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Thread: Need help with my gear (Phase One + ZD Back)

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    Senior Member MaxKißler's Avatar
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    Need help with my gear (Phase One + ZD Back)

    Hi everyone,

    first of all, thanks for taking your time to read this.

    I have to admit I'm not only new to this forum but also new to photography itself. I bought my first dslr in April this year and taught myself to take images and postprocess them. So I'm still devoloping myself and haven't figured out, which "photographic direction" to turn to. One thing's for sure, I do want to make my living out of it.

    Now I've recently discoverd MFD and it fascinated me so badly (I knew this was what I needed, without having to try it out first)... So I ended up, spending what I've got for a refurbished Phase One 645AF and a good as new ZD Back. It wasn't a difficult decision for me since I'm not the economical kind of guy anyway and I convinced myself with the thought, that if I someday want to play among the big boys, I better get to know the gear asap.

    On friday I received my first lens, a Mamiya AF 45mm f/2,8, which I thought might be a good focal lentgh for shooting handheld. Sadly I haven't discovered this forum earlier, as I just read that this lens might be total crap.

    Today's available light was good enough for my first test run but later on as I developed my raws I recognized a lot of, I don't know, is that chromatic abbaration? Especially when recovering dark areas. In almost every backlight shot I recovered, there are these purple shades. (Sorry, I'm not yet familiar with photographis terms in the English language).

    Now my actual questions are: Does this have something to to with the lens or is something wrong with my back? Are 12 bits per channel too less to effectively recover dark areas? Are the old Mamiya AF lenses "good enough" for the ZD Back?

    P1 645AF + ZD Back + 45mm @ ISO 100, 1/80s, f/8

    Attachment 37672

    Here's a 100% crop of what I was talking about.

    Attachment 37673

    ^^I hope this works.

    Thanks for your info of any kind!

    Max

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    Re: Need help with my gear (Phase One + ZD Back)

    Max - I'm new here as well and still asking questions but the guys are very helpful and I'm sure you will get an answer quickly - Most are based in the USA so on a different timezone to Europe

    Tim

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    Re: Need help with my gear (Phase One + ZD Back)

    The phrase you are looking for is "purple blobs" - a google search for "Mamiya ZD purploe blobs" will uncover a lot of information about this.

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    Re: Need help with my gear (Phase One + ZD Back)

    Looks like something is wrong with the back... did you buy it from a store? If so take it back! Off-hand I'd guess the coating on the IR filter is uneven or peeling.

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    Re: Need help with my gear (Phase One + ZD Back)

    Quote Originally Posted by dougpetersonci View Post
    The phrase you are looking for is "purple blobs" - a google search for "Mamiya ZD purple blobs" will uncover a lot of information about this.
    Well i am not getting those with mine.

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    Re: Need help with my gear (Phase One + ZD Back)

    Max, welcome to forum

    ZD is not very well handling pulling of shadows, in fact most of MFDbs are, except may be for newest ones (havent touched P65+ yet.. or newest Leafs.. MUST RESIST TEMPTATION).
    Looks like you did that in the image, to even out contrasts between sky and road.

    And secondly - what you used to process RAW?

    And thirdly - what white balance setting you used? (yes it does matter for even for RAW, trust me on this one)
    Last edited by SergeiR; 21st November 2010 at 16:43.

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    Re: Need help with my gear (Phase One + ZD Back)

    Thanks guys.

    I used the automatic white balance and later corrected it with Lightroom. I didn't know that white balance had an impact on raws. Good to know.

    Unfortunately I bought the back on ebay so there's no chance for an easy fix...

    Could it be possible, that the sensor is just dirty as hell? I have discovered a lot of dust particles on the sensor's surface. Sadly I can't yet clean it.


    Sergei,

    don't you get these "blobs" when recovering a severely underexposed image?
    Now you obviously own a ZD Back, how are your experiances with long exposures?

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    Re: Need help with my gear (Phase One + ZD Back)

    Quote Originally Posted by SergeiR View Post
    ZD is not very well handling pulling of shadows, in fact most of MFDbs are, except may be for newest ones
    That's absolutely untrue. Even a 2003 vintage Phase One H25 or 2004 era Leaf Valeo 17 can pull enormous (clean, color accurate, and natural looking) detail from deep underexposed shadows. That's one of the major advantages to use a digital back. That said: not every digital back is created equal...

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    Re: Need help with my gear (Phase One + ZD Back)

    How under exposed were the shadows. Can you post a sample of the shot before you boosted the shadows?

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    Re: Need help with my gear (Phase One + ZD Back)

    Quote Originally Posted by MaxKißler View Post
    Thanks guys.

    I used the automatic white balance and later corrected it with Lightroom. I didn't know that white balance had an impact on raws. Good to know.

    Unfortunately I bought the back on ebay so there's no chance for an easy fix...

    Could it be possible, that the sensor is just dirty as hell? I have discovered a lot of dust particles on the sensor's surface. Sadly I can't yet clean it.


    Sergei,

    don't you get these "blobs" when recovering a severely underexposed image?
    Now you obviously own a ZD Back, how are your experiances with long exposures?
    You may get better results in Capture One than LightRoom. However, I fear you may not find a great "fix" - this is a problem found/discussed by many (numerically - I have no idea % wise) ZD users, especially early in the life of the back - from my memory Mamiya addressed/fixed/improved it in later production, but to be clear I am NOT a ZD expert. I would contact your local Mamiya rep and see what their policy is. And read through the various threads that come up when you google "mamiya ZD purple blobs".

    Hopefully you can get it resolved!
    Last edited by dougpeterson; 21st November 2010 at 18:31.

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    Re: Need help with my gear (Phase One + ZD Back)

    Quote Originally Posted by dougpetersonci View Post
    That's absolutely untrue. Even a 2003 vintage Phase One H25 or 2004 era Leaf Valeo 17 can pull enormous (clean, color accurate, and natural looking) detail from deep underexposed shadows. That's one of the major advantages to use a digital back. That said: not every digital back is created equal...
    Doug - i tried to pull shadows when was deciding between Phase One and Leaf, about year ago. And i seen Drew Gardner doing same on his DVD with his P45+. Its getting real ugly real fast. May be these are just two occasions (well ok, i has same deal with Hassel, but i wont go there), i am sure you have access to wider array of gear than i am. So i am speaking purely from my personal experience - highlights - yes. Shadows , while it can pull out more details in general (having 16 bit of which 4 bits are roughly go to lower end of curve, so more details than dSLR) - pulling isnt something they are very good at. They do have more details from scratch, but if you go and pull them artifically - you getting "blooming" zones of weird colour noise, unless you getting it done with better RAW convertors (RAW Developer and C1 do come to mind - they handle it better.. just like Bibble used to be best for pushing highlights for about year, till everyone caught up ).

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    Re: Need help with my gear (Phase One + ZD Back)

    Quote Originally Posted by MaxKißler View Post
    Could it be possible, that the sensor is just dirty as hell? I have discovered a lot of dust particles on the sensor's surface. Sadly I can't yet clean it.


    Sergei,

    don't you get these "blobs" when recovering a severely underexposed image?
    Now you obviously own a ZD Back, how are your experiances with long exposures?
    you can just get filter glass off the ZD back and use dust blower to clean. Just be carefull as there is real sensor surface under there ))

    This is fairly unique feature of them - made them desired for IR photography for a while.

    --

    ZDs arent great with long exposures. I did up to 12s, and cleaned it in C1, and its somewhat useable.. But not in heat. Passive cooling makes this back lightweight , but prone to high temp == noise.

    Oh and - i do not pull shadows on normal basis (and when i did - my ZD is more or less ok on those blobs, except for some weird and rare occasions). I hate doing that with dSLRs and i dont like it with MFDbs. Thats why we have flashmeters I dislike to be off even by as much as stop. Only time when i do underexpose on purpose - when i have to build up array of images like sky + river, for gluing them later together. Everything else - i'd rather adjust settings on camera or light power, or move a bit. Photography is all about light and shadows. Got to control them But get a trial of C1 - they indeed do much better job on these things and you get some extra control over things - like moire removal.
    Last edited by SergeiR; 21st November 2010 at 19:22.

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    Senior Member MaxKißler's Avatar
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    Re: Need help with my gear (Phase One + ZD Back)

    I only have this problem when shooting directly towards the sun and later pull shadows. My light meter indicated an almost "proper" exposured and so did the histo on the back. However, these shadow areas might just be too underexposed?

    Since this is my first digital back and the first time I took some pictures with it, I simply don't have the experiance on how far one can go.

    Here are some examples.

    Attachment 37701 Attachment 37702

    @ Doug,

    I checked other forums as you implied and begin to lose hope after all I read on Luminous Landscapes.

    Now I just called Mamiya Germany and that guy said I should be using their software instead of C1 or LR. Somehow I don't think this will change anything...

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    Re: Need help with my gear (Phase One + ZD Back)

    Yeah, i thought about it a bit more when woke up this morning - most of those artifact-ish shadows you will ever get - will be in contra-light. In normal conditions you can get 2 stops out of shadows easy.

    PS: Mamiya got actual software for backs? Oy..
    But seriously - try C1 and instead of just getting expsure comp - try their shadow/highlight tool. It does wonders sometime.

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    Re: Need help with my gear (Phase One + ZD Back)

    Quote Originally Posted by MaxKißler View Post
    I checked other forums as you implied and begin to lose hope after all I read on Luminous Landscapes.
    Yeah, if you got to shoot for real you cant do it with anything less than arca cube, newest and greatest gear & etc.

    Or you can just shoot and enjoy it, working around limitations of your gear, while growing into new one. Choice is always yours

    - almost contra-light ZD on RZIIProD, with 140mm lens (while i couldnt figure how to get RZ to work with Leaf )




    - controlled light ZD on AFDIII (my Leaf was away for upgrades/calibration at MAC)



    - controlled light , ZD on AFD (one of first shots i made with ZD, when i got it)


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    Re: Need help with my gear (Phase One + ZD Back)

    Sergei,

    these are great shots indeed! If you might have plenty of spare time, would you please be so kind and do some tests with your back. I mean, if yours can pull details out of shadows comparable to mine above, we know for sure that my back is malfunctioning.

    Apart from that, I better live with these limitations which definitely won't stop me from enjoying this camera system. It's so much fun to take pictures with it.

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    Re: Need help with my gear (Phase One + ZD Back)

    Dallas got rainy days for whole week in forecast, but i will try to see what i can do with flashes - tonight or tomorrow.

    I dont really think you got any unique issues there - remember that asphalt on the road is pretty much gray, so when you starting to pull it - RAW processor will try to "invent" colours sometime, if it feels like there should be some colour

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    Senior Member MaxKißler's Avatar
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    Re: Need help with my gear (Phase One + ZD Back)

    Thanks a lot Sergei,

    I guess it is nothing to worry about since I'm not using it commercially anyway. I would love to know how a back with 16 bits would handle equal conditions.

    I would really appreciate if you could do some tests with your back!

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    Re: Need help with my gear (Phase One + ZD Back)

    Quote Originally Posted by SergeiR View Post
    ...
    But seriously - try C1 and instead of just getting expsure comp - try their shadow/highlight tool. It does wonders sometime.

    I agree that the software plays a big part on the outcome. Also, I've seen people having problems in LR and after creating a custom profile with the DNG editor (free from Adobe), the problems disappeared. The problems were similar to yours but the blotchines was not purple.

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    Re: Need help with my gear (Phase One + ZD Back)

    Quote Originally Posted by SergeiR View Post
    I dont really think you got any unique issues there - remember that asphalt on the road is pretty much gray, so when you starting to pull it - RAW processor will try to "invent" colours sometime, if it feels like there should be some colour
    Again, when you pull up shadow detail the quality of the result depends very heavily on the quality of the camera/back you were using and the quality of the raw convertor. If you pull up shadows and get large blobs of green/purple worms it points to sub-part quality of either the camera/back or raw convertor.

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    Re: Need help with my gear (Phase One + ZD Back)

    Doug,

    do you have any experience with equally underexposed images taken with a different back?
    Comparable to the two images I posted before.

    Maybe the ZD Back is just not good at contra-light shots? What do you think, is there something wrong with it? I get the same results no matter what raw developer I use...

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    Re: Need help with my gear (Phase One + ZD Back)

    I have been using my ZD for a while now.

    Quite simply, as a raw converter, Lightroom 2.6 sucks relative to the C1. I get tons of those weird green bits in the shadows from LR, where they are totally not there in C1.

    I more or less only use LR for the BW presets when using my ZD. Not near the same problem when converting Nikon.

    While you cannot pull the same detail, try shooting a JPEG, and it will eliminate the converter from the sequence. No green bits in the JPEG, and it's almost certainly not the hardware.

    On the other hand, clearly, when there is light, the ZD is a great value if you compare it to a D3X or a Canon Mark IV!

    Just my 2cents, YMMV.

    Dave

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    Re: Need help with my gear (Phase One + ZD Back)

    You're trying recover 3 to 4 stops of shadow detail in these images, and that's just not realistic. With a ZD you can boost the shadows 1 to 2 stops in most cases and be fine.

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    Re: Need help with my gear (Phase One + ZD Back)

    Quote Originally Posted by dougpetersonci View Post
    The phrase you are looking for is "purple blobs" - a google search for "Mamiya ZD purploe blobs" will uncover a lot of information about this.
    @ Max,

    The purple blobs was not same issue but another that photographer Frank Doorhof wrote of that was limited to a faulty ZDs in a certain batch/batches of ZD back only. What you are experiencing appear to be exact same as I wrote of under title "ZD has Problem" at www.luminous-landscape.com ; http://www.luminous-landscape.com/fo...?topic=22698.0

    Above was what I pointed out nearly three years ago. What I pointed out then was that there were from what I had learnt issues relating to the then "limited" design of the ZD - both hardware and firmware side. Leaf Aptus 22 has identical sensor from Dalsa and has per what I know not had same problem, thus what I was told in late 2007 frank makes sense. Per posts here on Getdpi I thought Phase One and Mamiya had reduced that problem, however what you show in photos seem very identical to way I would have expected my old ZD camera to perform. I sold it at loss because it was simply unusable product for my landscape photography, namely when you have much light and same time shadow in photo. However it also showed this when exposing neutral to test sample filling half frame with white and remaining with near black subject under diffused natural lighting indoors.

    I went with Leaf Aptus 65 and have had no similar problem.

    With above experience and I recommend you following:

    1. Get Capture One since it is developed by Phase One who owns major controlling share in Mamiya. If any software includes a fix to tune down the problem, it is likely Capture One. I also recommend that software because it is way better than any other raw converter I have used. Capture One also works excellent for my Leaf Aptus files with conversion profiles direct implemented with Leaf, thus if anyone have made good for ZD it must be them.

    2. It might not be popular among many, but crush the black by adjusting the black point to give less shadow details. That should reduce the problem.

    3. With Capture One PRO I can guess it can also work to tune down the issue by color adjusting with a narrow focus on the purple that ZD creates by using the color tool.

    4. I recommend testing your ZD back and doing so also of others in the shop you bought it from have. When Mamiya agent here in Hong Kong tested in early 2008 they found frank same problem on each ZD back and ZD camera they had in stock, simply by photographing a test chart with neutral exposure and observing purple in black frame on test chart...

    5. You may also wish to do a thorough search on www.luminous-landscape.com to read up on problems of ZD and what serial numbers those had to ensure that you was correctly sold a new and not old ZD. The critical is the last letter in ZD serial number (or was it the the first?). There is different numbering of ZD back and ZD camera.

    Regards
    Anders

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    Re: Need help with my gear (Phase One + ZD Back)

    Quote Originally Posted by MaxKißler View Post
    This looks like an IR hot spot. It's caused by optical reflections. Curiously I've only seen it on film with a Schneider 72XL (on 617) AND center filter. Taking off he CF would make it go away. In that case it was probably an IR reflection between the ND portion of the filter and front element of the lens. In your case, because the spot mimics the sky highlights I'd suspect it's a reflection that involves an in-focus part of the image path; almost certainly between the back of the lens and IR filter. A different lens might make it go away.

    It could also be something about early versions of the ZD back reflecting between the image chip and the IR filter. I've never seen it on mine though and I shoot into sun and bright sky a lot.

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    Re: Need help with my gear (Phase One + ZD Back)

    Thanks for all your help.

    It all sounds very plausible to me yet it's still confusing... Today I checked my images again and it appears to occur only on the lower bottom part when there is little contrast. Probably because those parts are most likely to be underexposed. As John suggested, it might be to much for the ZD to recover those details.

    @ John
    I read a lot on pebbleplace.com which also encouraged me to get the back and since you once owned a ZD camera I'm sure you know better how far one can push it and still get good results.

    @ Anders
    Yeah, I read those aswell. Unfortunately a refurbished Leaf Aptus 54 (not even the "s" version) costs about four times as much as the ZD Back so I won't regret my purchase that soon.

    @ Jan
    It will be difficult to check as I have to aquire another lens first... My budget is very very limited. ;-)

    Now the only thing that really bugs me is not to know whether some other ZD users might be able to pull shadows comparable to mine in the images obove with the same piece of equipment and without having these ugly blobs...

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    Re: Need help with my gear (Phase One + ZD Back)

    I've yet to see that kind of discoloration from any back ... all the way from my first Kodak Proback up to now. I wouldn't care what the cause was, it would be unacceptable. The issue is well documented.

    So, if I were you, I'd still explore returning the back as defective. I guess it will depend on how long it's been since you bought it off of e-bay (That was error number 1. Never buy without return privileges, and it's always better to buy from an authorized or highly trusted dealer). Have you contacted the seller?

    There are some limitations to a ZD, but this shouldn't be one of them. However, the images you posted are grossly underexposed. The only way to shoot something that's lit like that is to expose for the midtones and let the sky go ... or to make multiple exposures on a tripod and marry the images in post processing.

    -Marc

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    Re: Need help with my gear (Phase One + ZD Back)

    Max i owned the ZD back a couple years ago and actually my first back. Mine did not perform like this in anyway. To me this just flat out looks defective. I'm going to have to agree with Marc here.
    Photography is all about experimentation and without it you will never learn art.

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    Re: Need help with my gear (Phase One + ZD Back)

    Quote Originally Posted by fotografz View Post
    I've yet to see that kind of discoloration from any back ... all the way from my first Kodak Proback up to now. I wouldn't care what the cause was, it would be unacceptable. The issue is well documented.

    So, if I were you, I'd still explore returning the back as defective. I guess it will depend on how long it's been since you bought it off of e-bay (That was error number 1. Never buy without return privileges, and it's always better to buy from an authorized or highly trusted dealer). Have you contacted the seller?

    There are some limitations to a ZD, but this shouldn't be one of them. However, the images you posted are grossly underexposed. The only way to shoot something that's lit like that is to expose for the midtones and let the sky go ... or to make multiple exposures on a tripod and marry the images in post processing.

    -Marc
    One thing that was said around three years ago of ZD was that it needs ALOT of light. To my observation it seemed that people using it in studio and in sunny climates thus seemed to experience less purple artifacts, simply because they had alot of light. Again the purple blobs were looking different and were clear purple blobs, not what Max showed above. The purple artifacts on other hand (posted by Max above) showed up in shadow and darker areas, just like did on mine (even around -2 stop). There must still be numerous such ZD floating around on used market thus one can urge people to be cautious. One could wish Mamiya would have been honest and took them all back... and reimbursed us who lost on them... However, what I stated above can possibly help to tune down the problem, as of course to use it in conditions with lots of light and reasonably even light. Do try Capture One. Newer ZDs may partially be much improved due to Capture One and maybe some firmware fix to tune down the issue. However, one could guess that Phase One did not spend too much $$ into ZD, thus did not fix hardware part. At least that is my guess. Reading between the lines, simply seemed they failed to proper develop ZD and released it to bring in revenue... Will not comment my personal opinion.

    Max, please post back more of what direction you take and what you discover. Will be interesting to hear of. One could hope that software and firmware side to have improved in three years time. And sincere wish you best luck. And yes, my Aptus 65 cost me $$ and I bought new. It was f^&*^%#@ spent of $, simply because wanted have quality digital to enjoy advanced digital photography, not dslr. The contrast with Leaf is also truly excellent support, and fast such. For expensive gear that and reliable is very important.

    Regards
    Anders
    Last edited by Anders_HK; 23rd November 2010 at 04:09.

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    Re: Need help with my gear (Phase One + ZD Back)

    Quote Originally Posted by Anders_HK View Post
    @ Max,

    The purple blobs was not same issue but another that photographer Frank Doorhof wrote of that was limited to a faulty ZDs in a certain batch/batches of ZD back only. What you are experiencing appear to be exact same as I wrote of under title "ZD has Problem" at www.luminous-landscape.com ; http://www.luminous-landscape.com/fo...?topic=22698.0
    Posts like this is why GetDPI is such a great resource! Thanks for taking the time to elaborate so fully on your experience.

    Thanks!

    P.S. semantics wise I think for many people "purple blobs" became a descriptor of BOTH the worm issue and the very-low-frequency shadow color accuracy issue.

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    Re: Need help with my gear (Phase One + ZD Back)

    Quote Originally Posted by dougpetersonci View Post
    Posts like this is why GetDPI is such a great resource! Thanks for taking the time to elaborate so fully on your experience.

    Thanks!
    I can only agree to that .
    Regards . Jürgen .
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    Re: Need help with my gear (Phase One + ZD Back)

    As I have said, before, if the ergonomics of the ZD were better, I would be thrilled with the price performance ratio. When Processed in C1, mine seems to hold both highlights and shadaows pretty well. I'm not in the position where I have a good feeling for how many stops, but way better than my D300. The following crops show both resolution and ability to get highlight detail.

    Nikon 100% crop:
    50mm lens 1.8, 1/500


    Mamiya:

    150mm 3.2 1/500

    ( I'm have not gone to DOF master, but I'm confident, they are both thin!)

    Note the details in the fine hairs above the lips, and the lips. I think the Mamiya is better.

    Going back and reviewing, I would say the character of the my problem areas in the shadows in not near the same type of greens as the OP. I'll post some examples soon.

    Dave

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    Senior Member MaxKißler's Avatar
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    Re: Need help with my gear (Phase One + ZD Back)

    Hi everyone,

    I did some rudiculous test shots today and it appears to be some sort of reflections that only appear in underexposed parts of an image. I shot towards lit windows while the foreground was underexposed. When I processed the files and pulled up shadows, purple areas in the shape of my windows appeared. Especially when these parts where underexposed below 3 f stops. I'll redo this test tomorrow and show you the results.

    I still believe this happens due to the 12 bits which don't seem to have enough colour information.

    @ Anders
    Thanks for sharing your experiences. As I already mentioned I bought it via ebay so there is no chance of returning it. I agree with you that Mamiya should have taken action in the first place. However, the back works fine, except for those "contra-light" situations and I really enjoy using it.

    BTW I didn't expect the AF on my PhaseOne body to be that fast!

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    Senior Member MaxKißler's Avatar
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    Re: Need help with my gear (Phase One + ZD Back)

    @ Dave
    My ZD Back works quite well under controlled conditions, even if I'm just using my tiny Metz flash. What I'm concerned about are these weird magenta reflections occurring only when shooting towards the source of light.

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    Senior Member Steve Hendrix's Avatar
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    Re: Need help with my gear (Phase One + ZD Back)

    Quote Originally Posted by MaxKißler View Post
    Hi everyone,

    I did some rudiculous test shots today and it appears to be some sort of reflections that only appear in underexposed parts of an image. I shot towards lit windows while the foreground was underexposed. When I processed the files and pulled up shadows, purple areas in the shape of my windows appeared. Especially when these parts where underexposed below 3 f stops. I'll redo this test tomorrow and show you the results.

    I still believe this happens due to the 12 bits which don't seem to have enough colour information.

    @ Anders
    Thanks for sharing your experiences. As I already mentioned I bought it via ebay so there is no chance of returning it. I agree with you that Mamiya should have taken action in the first place. However, the back works fine, except for those "contra-light" situations and I really enjoy using it.

    BTW I didn't expect the AF on my PhaseOne body to be that fast!
    Max

    In my opinion, there is probably nothing wrong with your back.

    At ISO 100, you are 2 stops pushed from the base ISO of 25. If you push underexposed low key subject matter 2 stops with anything, this or something like it will often be the result.

    Attached below is a crop of an ISO 400 shot from the same sensor pushed 2 stops (though in a Leaf Aptus 22).

    There are ways to reduce the effect, sometimes just using a white balance dropper to click on the area, if it is a reasonably neutral area, like a sidewalk or a street. Also, you can use the Color Editor in Capture One to select the purple globs and desaturate them.


    Steve Hendrix
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    Re: Need help with my gear (Phase One + ZD Back)

    I went out to my files, and pulled an example a bit more severe than the one Steve shows above. I think that it really points out what is by now all too well know, the ZD is a good light back.


    This is at ISO 400, and with a continuous light source, both highlights and shadows opened up full on the C1 sliders. In this silly case, we get both green and purple artifacts.

    I'm not sure how a "modern" back would deal with this, but that is one that that I would expect to be better on the newer ones.

    For my use, in almost all cases, I can just crank up the power on the strobes and shoot at ISO 50/F8, and there, the ZD is just fine.

    Dave

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    Senior Member Steve Hendrix's Avatar
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    Re: Need help with my gear (Phase One + ZD Back)

    Quote Originally Posted by djonesii View Post
    I went out to my files, and pulled an example a bit more severe than the one Steve shows above. I think that it really points out what is by now all too well know, the ZD is a good light back.

    This is at ISO 400, and with a continuous light source, both highlights and shadows opened up full on the C1 sliders. In this silly case, we get both green and purple artifacts.

    I'm not sure how a "modern" back would deal with this, but that is one that that I would expect to be better on the newer ones.

    For my use, in almost all cases, I can just crank up the power on the strobes and shoot at ISO 50/F8, and there, the ZD is just fine.

    Dave

    I would say modern backs handle this better, though it is still a situation that I would try to avoid or use best practices to reduce the effect in post.


    Steve Hendrix
    Steve Hendrix, Sales Manager, www.captureintegration.com (e-mail Me)
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    Re: Need help with my gear (Phase One + ZD Back)

    All backs fall apart somewhere. The pertinent question is when and how.

    The examples posted by Dave and Steve show grain and low frequency color noise.

    The examples posted by the OP show grain and ULTRA LOW frequency color noise which more or less looks like large color banding.

    Low frequency color noise can be relatively easily removed by increasing color noise suppression. Large areas of color banding are much more troublesome to deal with in post.

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    Re: Need help with my gear (Phase One + ZD Back)

    Quote Originally Posted by MaxKißler View Post
    I still believe this happens due to the 12 bits which don't seem to have enough colour information.
    afaik it is 14 bits.

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    Re: Need help with my gear (Phase One + ZD Back)

    Quote Originally Posted by Steve Hendrix View Post
    M
    At ISO 100, you are 2 stops pushed from the base ISO of 25. If you push underexposed low key subject matter 2 stops with anything, this or something like it will often be the result.

    i think ZD starts with 50, at least mine is.

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    Senior Member Steve Hendrix's Avatar
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    Re: Need help with my gear (Phase One + ZD Back)

    Quote Originally Posted by SergeiR View Post
    i think ZD starts with 50, at least mine is.
    I only know the base ISO of the sensor in the ZD is the same as the Aptus 22 (and Aptus 54, 54-S, II-5), and Jenoptik M22, by the way. The base iSO for all of the Aptus products using that sensor is 25 and I believe the M22 was also 25. I think one time we metered at the 25 setting and it was closer to 18 ISO...

    Regardless of the starting available ISO on the ZD, I consider the base ISO to be at 25 and if 50 is the start, it is already pushed.

    And this attached result can be achieved with the Color Editor pretty easily, and even improved from this with just a bit more effort.


    Steve Hendrix
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  42. #42
    Senior Member MaxKißler's Avatar
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    Re: Need help with my gear (Phase One + ZD Back)

    Quote Originally Posted by SergeiR View Post
    afaik it is 14 bits.
    IMO it has a 14bit ADC but the files are downsampled to 12bits per channel.

    However, I'm relieved for I'm sure to have almost solved that purple area mystery! At least it makes perfect sense to me.

    This is it:
    When the camera is pointed towards the source of light and in the moment the sensor is exposed, light is reflected by the IR-Cut filter towards the back of the lens. These reflections are mainly red/magenta like the surface that reflects the light (the IR-Cut filter). Now this light again is reflected by the back of the lens and now passes the IR-Cut filter leaving a little red/magenta colour information in the shadow parts. When I'm pulling shadows the red/magenta areas appear because they dominate over other colour information. This only appears in the shadows as there is enough information in the highlighted areas.
    So I guess it has something to do with the back of the lens, probably the (missing?) coating. Since it is not the 45mm D lens which I believe was mainly designed for digital purposes. So the Mamiya AF 45mm lens is not well coated as film didn't reflect?

    That only leaves one question:
    Why is light reflected by the sensor's filter? Does the filter let only a certain "amount" of light pass thru? Does that even make sense?!

    I'm going to post some samples tommorrow to support my thesis.

    Thank you Mr. Brittenson, you already gave the answer to this, only didn't I think of it long enough.

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    Re: Need help with my gear (Phase One + ZD Back)

    Quote Originally Posted by MaxKißler View Post
    Why is light reflected by the sensor's filter? Does the filter let only a certain "amount" of light pass thru? Does that even make sense?!
    Every piece of glass has a transmission rate, which by definition means not 100% of the light passes through it. Generally the better quality the glass the higher the transmission rate. As a case study look up the transmission rates of variously priced UV filters.

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    Senior Member MaxKißler's Avatar
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    Re: Need help with my gear (Phase One + ZD Back)

    Quote Originally Posted by MaxKißler View Post
    That only leaves one question:
    Why is light reflected by the sensor's filter? Does the filter let only a certain "amount" of light pass thru? Does that even make sense?!
    I realised how stupid the question was or at least how stupidly phrased right after posting it... I thought the IR-Cut filter might absorb that amount of light instead of reflecting it.

    Do you think some kind of filter might minimize that effect?

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    Re: Need help with my gear (Phase One + ZD Back)

    Quote Originally Posted by MaxKißler View Post
    I realised how stupid the question was or at least how stupidly phrased right after posting it... I thought the IR-Cut filter might absorb that amount of light instead of reflecting it.

    Do you think some kind of filter might minimize that effect?
    No.

    Return the back if you can and hunt down a later model where the issue was fixed.

    -Marc

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    Re: Need help with my gear (Phase One + ZD Back)

    Quote Originally Posted by Steve Hendrix View Post
    Max

    In my opinion, there is probably nothing wrong with your back.

    At ISO 100, you are 2 stops pushed from the base ISO of 25. If you push underexposed low key subject matter 2 stops with anything, this or something like it will often be the result.

    Quote Originally Posted by djonesii View Post
    For my use, in almost all cases, I can just crank up the power on the strobes and shoot at ISO 50/F8, and there, the ZD is just fine.
    This was the limitation of the ZD. Or in essence, it was not a product useful within all photographic situations that 50 ISO film was. Thus my impression was (and remain) that it was a clear faulty product, and that at least those old ZDs remain wrong with - a.k.a. they are capable only within a more narrow use than 50 ISO film.

    On the contrary, the Aptus 22 with same identical sensor from Dalsa was apprant not having same problem. See Frank Doorhof's review of ZD and read of his jump to Aptus 22 years back http://www.doorhof.nl/blog/index.php?board=11.0. In Luminous-Landscape forum is also much old written of ZD.


    Quote Originally Posted by MaxKißler View Post
    I realised how stupid the question was or at least how stupidly phrased right after posting it... I thought the IR-Cut filter might absorb that amount of light instead of reflecting it.

    Do you think some kind of filter might minimize that effect?
    No idea. You might try an IR block filter on lens filter thread similar to Leica M8 instead of the one in ZD body. You might find used ones but I have no idea if it will work better.

    To shoot IR you could instead of buying the ZD IR pass filter remove the ZD IR block and install an IR pass on lens filter threads. That might be cheaper, since possibly more available as used.

    You could also process as BW, in which case the purple problem would no longer be purple...

    - - -

    In all of this time of ZD... it seem remarkable that Mamiya remains quiet of the problem or any fix, is it not???

    Regards
    Anders
    Last edited by Anders_HK; 24th November 2010 at 16:21.

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    Senior Member MaxKißler's Avatar
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    Re: Need help with my gear (Phase One + ZD Back)

    Quote Originally Posted by Anders_HK View Post
    No idea. You might try an IR block filter on lens filter thread similar to Leica M8 instead of the one in ZD body. You might find used ones but I have no idea if it will work better.
    Thanks Anders,

    that's a great idea! It should definitely solve that problem and is way cheaper than buying a "D lens" which is out of my reach ATM.
    Sadly, I didn't have the same light conditions otherwise I would have showed you why I concluded that these purple spots are IR-Cut filter reflections.

    Kind regards
    Max

  48. #48
    Senior Member ondebanks's Avatar
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    Re: Need help with my gear (Phase One + ZD Back)

    Max,

    I've been following the ZD colour blotches issue for a long time, and from all the evidence I've seen, I don't believe that it is a case of reflections. In your park sunset image (MMFC0079-2.jpg aka attachment 37702), the geometry is all wrong to invoke sensor/IR filter/lens reflections as the cause of the purple blotches. They should be strongest on a line passing through both the brightest thing in the image (the sun) and the central axis of the image/system. They are nowhere near that line. They are also too irregular in outline. Nor do they mimic the sky in either size or shape. Sorry, but that theory does not fit the data!

    It's also unconnected with the bit depth. Lots of backs have 12 bits depth (including my Kodak Proback 645M), and they don't show this effect. In my astrophotography, I sometimes have to push at least as much as the 2 stops you and Steve have shown, and my Kodak does not behave like this. Such as, I shoot at ISO 400 (2 stops above base ISO of 100) and then push it another stop or two!

    I'm afraid that's all I can do regarding this colour blotch problem: I can tell you that it's not some of the things you thought it might be; but I cannot tell you what it is. It is the oddest behaviour that I've seen from a CCD sensor. How does one explain colour correlations over such large scales?

    Pixel to pixel variations in the flatfield response are normal, but it's not that either - if it were, then the blotches would be just as visible at high signal levels, but of course they're not.

    The same reasoning rules out any other multiplicative/percentage-of-signal line of thinking, such as localised variations in the Bayer filters.

    No: the problem is only visible at low signal levels, and that points to additive/subtractive effects. The reflections idea falls into this category which is why it would indeed be logically sensible, but as I've already said, it just doesn't seem to work.

    My guess (and that's all it is) is that if a bias calibration frame is internally subtracted, it is "awry" over moderate scales: too much or too little bias is being subtracted from groups of pixels. Just a few counts of bias error could upset the low-signal RGB colour ratios over these scales.

    Since bias calibration would be under Mamiya's control and embedded in their firmware, it follows that other backs (like Leaf) with the same sensor would not show the same effect, and that the problem could have been solved by Mamiya by the time they released the second generation of ZD backs. In other words, it's a theory which fits the data, but better data might well prove it wrong!

    Ray

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    Re: Need help with my gear (Phase One + ZD Back)

    Well i can happily say that i seen same issue on Aptus + C1 processing other day on couple of shots Available contra-light, and stange bit of colour in picture, when pulled up about 2.7 steps.

    Which leads me to believe that idea about funky re-reflections may be not very far from true

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    Re: Need help with my gear (Phase One + ZD Back)

    Ah, but where is the strange bit of colour occuring? And does it look like normal lens flare? I've seen a mild pink spot in the centre of my Kodak's images when shooting the moon at a frame-filling magnification, through a complicated relay of optics. That may involve a small reflection off the IR filter. But it is visible at high signal levels.

    Anyway - there is a very easy way to test if this is due to reflections or not. Photograph a uniform scene (e.g. a white wall or ceiling) with your ZD or Aptus with a small aperture (not wide open), and heavily underexpose it, so that it is all recorded at the sort of shadow image intensity where you see the colour blotches. If you see the blotches in this frame, it must be inherent to the sensor or firmware, not am optical reflection - because why would a flat, uniform illumination of the entire sensor cause reflections which create blotches only in certain scattered groups of pixels?

    Max, I recommend that you try that test.

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