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Thread: How different are the P45+ and P30+ as regards long exposures and noise levels?

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    How different are the P45+ and P30+ as regards long exposures and noise levels?

    I finally put my Contax/P30+ combo into service tonight with an outing to Miami, Arizona for some nighttime photography. Unfortunately, the initial results are not very promising, as (IMO) the images started to become excessively noisy after just 45 seconds of exposure at ISO100. (I also had some problems with the Contax 35mm lens creating ghosts whenever there was a strong light source in or just outside of the frame, despite using a lens shade and despite using a gobo to further shade the lens from direct light as much as possible. But I digress...)

    The ambient temp was in the low to mid-80s range and according to Capture One's handy chart, the back should have been good for exposures as long as several minutes at these temps. But either my tolerance for noise is lower than for most people or my back isn't performing up to snuff, as the noise levels I experienced with tonight's batch of images are clearly excessive.

    Anyway, while I wasn't planning on upgrading to a P45+ just yet, if it's a much better performer than the P30+ for long exposures, I may need to look into this as I fear the alternative may be for me to punt on medium-format digital and (don't laugh!) return to the various m4/3 setups with which I have been surprisingly successful previously.

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Did you have a filter on the Zeiss 35mm?

    -Marc

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    What raw converter were you using, and what were the NR settings? You should have had very little noise at 45 seconds.
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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Quote Originally Posted by fotografz View Post
    Did you have a filter on the Zeiss 35mm?

    -Marc
    Nope. The scenes I photograph are illuminated by streetlights, so this has been a problem before with other lenses, but not to this extent. Usually, so long as I can block the light from the streetlight overhead from striking the lens, ghosting isn't a problem, but not so with the 35mm lens. I didn't compare them back to back, but I did briefly use the 45mm lens as well and didn't have any problems with it.
    Last edited by Audii-Dudii; 4th September 2010 at 05:42.

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Quote Originally Posted by Jack Flesher View Post
    What raw converter were you using, and what were the NR settings? You should have had very little noise at 45 seconds.
    I am using the latest version of C1 but I don't recall the NR settings off the top of my head and am at my office right now, so I can't check on this until I get home later today. I will admit to being very new to C1 -- I only started using it earlier this week! -- so maybe I'm doing something wrong (or at least not optimally) there? Oh, and the back has the latest version firmware installed, too.

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    I'm a bit surprised by this . I had the P30+ do up to 35 minutes. Sure some noise but was pretty minimal. Now that was in cooler weather. Question how warm was the back to start with. I reside in AZ as well and right now a cam just sitting in the car for 10 minutes is deadly hot. Now the P30+ has micro lenses and the angle of the street lamps could possible be ghosting with a wide lens. That is very possible IMHO.
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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    P30+ ISO 100 at 35 minutes

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Re ghosts: One problem with older lenses before digital was rear element coatings. With digital, you get more reflection off the sensor glass back toward the rear lens element than you did with film. This can show up as fairly prominent ghosting when these lenses are used with digital, especially when strong, point-source light is in the frame. Newer generation lenses have been designed to help attenuate this. Of course filters, especially un-coated ones, can cause a similar effect from the front element bounce-back too.

    Re noise: That's a weird one. Can you post an example of the image with excessive noise at 45 seconds, full frame and a crop of the bad area?
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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Quote Originally Posted by Guy Mancuso View Post
    I'm a bit surprised by this . I had the P30+ do up to 35 minutes. Sure some noise but was pretty minimal. Now that was in cooler weather. Question how warm was the back to start with. I reside in AZ as well and right now a cam just sitting in the car for 10 minutes is deadly hot.
    Your comment about temperature has caused me to ponder a bit. Although last night was my first formal outing with the Contax/P30+ combo, I've used it several times before around my neighborhood as I was getting to know it, and the ambient temps on those occasions have all been in the upper 90s and the back became noticeably warm to the touch in use -- hot, even -- yet I don't recall having any significant noise problems then. That said, though, those exposures were all in the 10-30 second range, which is consistent with my experience last night.

    I don't recall the back getting anywhere near that warm last night, but due to some operational issues I was having with focusing and composing images in the dim light, I was forced into composing and focusing images iteratively by tweaking the camera position and focus distance by reviewing the prior image on the LCD, which meant in some instances, I was banging off images more-or-less consecutively for 15-20 minutes as I homed-in on the final image. So even though the exposures were only 45-120 seconds long, the back was on (although idling at times) for a much longer period of time. Prior to this, I was turning off the back between images to keep it cool, but these were also the shorter exposures, so I'm not sure I can separate the effects at work here without some further testing / analysis.

    Oh, and I apologize for starting this thread without posting any images to illustrate what I mean. It was sort of a knee-jerk reaction at the end of a disappointing evening and I'm now away from my home computer and don't have access to them ... doh! <*smacks forehead*>

    Now the P30+ has micro lenses and the angle of the street lamps could possible be ghosting with a wide lens. That is very possible IMHO.
    Hmm ... I hadn't thought of that. Interesting...

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Quote Originally Posted by Jack Flesher View Post
    Re ghosts: One problem with older lenses before digital was rear element coatings. With digital, you get more reflection off the sensor glass back toward the rear lens element than you did with film. This can show up as fairly prominent ghosting when these lenses are used with digital, especially when strong, point-source light is in the frame. Newer generation lenses have been designed to help attenuate this. Of course filters, especially un-coated ones, can cause a similar effect from the front element bounce-back too.
    I realize that Contax / Zeiss lenses were designed before digital backs had become common, but they definitely existed at that point in time and surely Zeiss considered this factor in spec'ing its coatings? In any event, prior to buying into the Contax system, I searched the 'net rather thoroughly looking for info about the performance of the lenses -- scoured it, even! -- and I can't recall anybody, anywhere ever mentioning this as a problem with the 35mm lens. That said, I'll admit the type of photography I do is a bit unique, so it's certainly possible that I'm the first person to ever use it in precisely this manner ... who knows?

    Re noise: That's a weird one. Can you post an example of the image with excessive noise at 45 seconds, full frame and a crop of the bad area?
    Um, yeah. That was a bit of a bonehead manuever on my part, wasn't it? When I get home later today, I'll post some examples.

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Quote Originally Posted by Audii-Dudii View Post
    I was banging off images more-or-less consecutively for 15-20 minutes as I homed-in on the final image. So even though the exposures were only 45-120 seconds long, the back was on (although idling at times) for a much longer period of time.
    This probably explains it as the heat build-up on the sensor is somewhat cumulative without adequate downtime between frames. I would guess what you were seeing is equivalent to the noise generated with a 15 minute or so exposure because of this; and 15 minutes at 80 degrees would be pretty noisy I think...
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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Quote Originally Posted by Guy Mancuso View Post
    P30+ ISO 100 at 35 minutes

    LOL ... you have posted this photo before and it was definitely one of the factors that pushed me to buy a P30+. So, in a roundabout way, I guess this means I can blame you for putting me in this situation?

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Quote Originally Posted by Audii-Dudii View Post
    I searched the 'net rather thoroughly looking for info about the performance of the lenses -- scoured it, even! -- and I can't recall anybody, anywhere ever mentioning this as a problem with the 35mm lens.
    Well maybe... But I owned and shot Contax MF, including the 35mm lens, for several years with film before Kodak released the DCS Pro back for it. I recall occasional ghosting in direct light conditions with that camera and digital back that I never noticed with film, but then I am older and it was a long time ago, so maybe my memory is flawed. Regardless, if it was due to the microlenses on your P30+ back, I would think the image of Guy's above would show it with the car lights in the frame...
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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Quote Originally Posted by Jack Flesher View Post
    This probably explains it as the heat build-up on the sensor is somewhat cumulative without adequate downtime between frames. I would guess what you were seeing is equivalent to the noise generated with a 15 minute or so exposure because of this; and 15 minutes at 80 degrees would be pretty noisy I think...
    Having slept on this overnight, this was one of the explanations I've come up with as well, which raises the obvious question as to how much downtime between exposures is necessary for low-noise performance? It looks like I'll need to do some more testing, especially as I typically bracket my images in groups of three, which means even shorter exposures will require the back to be on for several minutes at a time.

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Well general rule at least for me is if you feel warmth on the bottom of the back than turn it off before doing a long exposure. If your running them constantly your just building heat and in 80 degrees this will be even harder since the back will get warm after the first 15 minute shot. They simply will build heat. In cooler weather this is not a issue since it rarely will get warm but when you hit the 80 mark it almost pays to go for one than turn it off for awhile and cool the back down.
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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Quote Originally Posted by Audii-Dudii View Post
    LOL ... you have posted this photo before and it was definitely one of the factors that pushed me to buy a P30+. So, in a roundabout way, I guess this means I can blame you for putting me in this situation?
    LOL been blamed for a lot worse.

    Guess i emptied a few bank accounts along the way as well. Such a devil

    But seriously the P30+ is a great back no question about it and even though it maybe rated to a hour and in cold weather it maybe . I found 35 minutes in 55 degrees pretty good. Not sure I personally would push it further and I have seen Jack go the full hour on the P45+ the same night and he had awesome results
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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    "I have seen Jack go the full hour on the P45+ the same night and he had awesome results?" Do you bring chairs, or sit in the car?

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    From hotel balcony . LOL


    I should add C1 is your answer also with long exposure noise control now in version 5 and also working with luminance and color noise controls you can really get awesome results.
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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    I haven't owned a Phase back on a while so I don't remember if the dark frame is automagic. Is the 30+ exposing a dark frame to subtract at the end of the exposure? I used to shoot a P21, non plus, for 35 minutes at a time with awesome results.

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Yes they do a dark frame as long as your exposure is
    Photography is all about experimentation and without it you will never learn art.

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    1) Absolutely essential (for best results) to ensure your back has the latest firmware. Check under Menu > Configuration > About. If you don't have 5.1.2, and especially if you have something very old like 2.9.8 you will see much better results with longer exposures. More Info.

    2) If you shoot four four-minute exposure in a row (just to select a specific example) without allowing the back to cool down then the noise in the image will be similar to a sixteen minute exposure. It's perfectly reasonable to adopt a workflow whereby you shoot as many frames quickly as you need to asses framing/exposure etc (including using high ISO images to estimate final proper exposure) and then wait a few minutes before capturing the "keeper".

    3) Judging the back's temperature is not something that's really that easy to do. The entire chasis is constructed as a big heat sink, so it's not only normal to see the outside frame become warm/hot - it's the entire point! The only temperature that matters for long exposure noise purposes is the internal temperature of the back. The heat is pulled away from the sensor/A-D convertor to the exterior of the back where a large surface area can dissipate that heat into the air quickly (and without a fan).

    4) Capture One versions and raw processing settings also matter a lot. Keep in mind that if you "push" the file one stop in post (a.k.a. +1 Exposure in C1) means you are effectively doubling the length of the exposure in post. So if you're temperature-limit was 10-minutes and you expose in-camera for 5 minutes and then slide exposure up to +1 in Capture One you will be going past the "maximum" - the world will not end but your noise levels will likely be higher than you want. The same principal applies to any image adjustment which increases exposure in the shadows (e.g. shadow recovery, curves, lens-vignette or LCC adjustments). NEVER try Lightroom/Aperture/etc/etc to process long exposures from Phase One - stick with Capture One, and specifically stick with Capture One 5.1.2 (or whatever the latest is when you read this).

    With all that in mind: a P30+ back with recent firmware and which is shot when it's had a chance to cool off will behave very much in accordance to Phase One Long Exposure Guide which we have on our website. That of course is showing the maximum, so it's always a good idea to be conservative where possible.

    P.S. Our company name is "Capture Integration", not "Capture One" (no worries of course - I just thought I'd clarify to avoid confusion of any other readers).

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Thanks for the clarifications Doug! And FWIW, as respects the names, I often use "CI" when referring to Capture Integration, and "C1" when referring to PhaseOne's Capture One processing software -- it's unfortunate the letter *I* and the number *1* look so similar online. My bad.
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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Quote Originally Posted by dougpetersonci View Post
    2) If you shoot four four-minute exposure in a row (just to select a specific example) without allowing the back to cool down then the noise in the image will be similar to a sixteen minute exposure. It's perfectly reasonable to adopt a workflow whereby you shoot as many frames quickly as you need to asses framing/exposure etc (including using high ISO images to estimate final proper exposure) and then wait a few minutes before capturing the "keeper".
    Last night, I did some more testing instead of photographing (grrr...) and confirmed that shooting several long exposures virtually consecutively does indeed appear to have been the source of my noise problem. What's not yet clear, though, is how long I should allow the back to cool between exposures to prevent noise from being a problem in the future. Or if this can be sped up any by providing some external cooling via a fan, as I am often setup in the middle of a street and the local police prefer that I disrupt traffic for as short a period of time as possible.

    4) Capture One versions and raw processing settings also matter a lot. Keep in mind that if you "push" the file one stop in post (a.k.a. +1 Exposure in C1) means you are effectively doubling the length of the exposure in post. So if you're temperature-limit was 10-minutes and you expose in-camera for 5 minutes and then slide exposure up to +1 in Capture One you will be going past the "maximum" - the world will not end but your noise levels will likely be higher than you want. The same principal applies to any image adjustment which increases exposure in the shadows (e.g. shadow recovery, curves, lens-vignette or LCC adjustments). NEVER try Lightroom/Aperture/etc/etc to process long exposures from Phase One - stick with Capture One, and specifically stick with Capture One 5.1.2 (or whatever the latest is when you read this).
    I understand the relationship between tweaking the image and increasing the presence of noise, but I wasn't aware that the relationship between doing so pre- and post-exposure is 1:1, which is how I read your comments. In any event, I am using the latest version of Capture One and it does appear that I was not using its NR tools aggressively enough. Needless to say, I'm looking forward to the Capture Integration (see? I got it right this time!) Capture One seminar in October as I have a lot of learning to do before I'm able to master it!

    Oh, and for the record, my P30+ also has the latest firmware version installed, as that's how I received it fresh from Denmark after it was replaced during my recent Hasselblad H-to-Contax mount conversion.

    With all that in mind: a P30+ back with recent firmware and which is shot when it's had a chance to cool off will behave very much in accordance to Phase One Long Exposure Guide which we have on our website. That of course is showing the maximum, so it's always a good idea to be conservative where possible.
    In view of my experience, perhaps you might consider adding a third note to the chart to the effect that multiple consecutive long exposures can equal the effect of a single long exposure of the same length? In retrospect, this seems fairly obvious, I know, but I'm generally not a dumb guy and I didn't consider this until it smacked me upside the head this past Friday night.

    Getting back to my original question, though: If the P45+ is the best Phase One has to offer as regards long exposures, are you able to quantify how much better it is than the P30+? While I would prefer to let my budget recover a bit before I think about upgrading, if the difference between them is significant enough -- say, 20%, whatever that might mean -- I might consider it anyway as many of the images I capture are quite ephemeral and I may not have a chance later to capture them again.

    P.S. Our company name is "Capture Integration", not "Capture One" (no worries of course - I just thought I'd clarify to avoid confusion of any other readers).
    Yet another instance of brain fade on my part. My apologies...
    Last edited by Audii-Dudii; 5th September 2010 at 09:52.

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Quote Originally Posted by Audii-Dudii View Post
    Getting back to my original question, though: If the P45+ is the best Phase One has to offer as regards long exposures, are you able to quantify how much better it is than the P30+? While I would prefer to let my budget recover a bit before I think about upgrading, if the difference between them is significant enough -- say, 20%, whatever that might mean -- I might consider it anyway as many of the images I capture are quite ephemeral and I may not have a chance later to capture them again.
    In my experience the P45+ is a bit better than the 30+ in regards to long exposure. I can't offer a technical explanation as I believe the difference is more than the obvious: smaller noise size for any given print size because of the higher resolution. However my experience is enough to indicate it'd be worth it for you to do your own further testing.

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Quick reminder note: the P30+ has microlenses while the P45+ does not. The base ISO of the P30+ is therefore ISO100 while the P45+ has a base ISO of 50. When I said the 45+ was slightly better than the 30+ at long exposures I meant in terms of being able to achieve the longest exposure in minutes for any given temperature. This equation may change if instead you are trying to gather the right amount of light for an exposure in a given fixed-lighting scene where the one stop gain in ISO may negate the higher ceiling in minutes.

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    FWIW,

    Here is a 30 minute capture at ISO *100* off the P45+. I used ISO 100 because I only had about 1/4 battery left and wasn't sure it would hold for a full hour. In the end, I still had a 1/4 battery after the 30 minutes of exposure and 30 of darkframe, so for whatever reason the backs don't seem to use a lot of power during the long exposure process:

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Quote Originally Posted by dougpetersonci View Post
    This equation may change if instead you are trying to gather the right amount of light for an exposure in a given fixed-lighting scene where the one stop gain in ISO may negate the higher ceiling in minutes.
    Well, since lighting rarely gets more fixed than it does with streetlights, which is how the scenes I photograph are illuminated, it sounds like the only benefit I'll see from a P45+ versus my P30+ are larger files and higher resolution.

    FYI, in case anybody is curious, here's the very first image I captured with the Contax/P30+ combo ... clearly, I still have a learning curve to climb here but aside from the noise issues, the results thus far do seem promising.


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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Quote Originally Posted by Jack Flesher View Post
    FWIW,

    Here is a 30 minute capture at ISO *100* off the P45+. I used ISO 100 because I only had about 1/4 battery left and wasn't sure it would hold for a full hour. In the end, I still had a 1/4 battery after the 30 minutes of exposure and 30 of darkframe, so for whatever reason the backs don't seem to use a lot of power during the long exposure process:

    Really beautiful image, Jack.
    However, even at this size the top area looks slightly noisy. Maybe it's just the web compression. Could you show a 100% crop from the top right area?

    -Dominique

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Dominique, I could dig the original up, but I can tell you it is a "noisy" image by any conventional measure. In fact, it is a good argument to stick to base ISO with these backs when doing long exposures. On the upside, the noise is only obvious in the even-toned areas -- which in this image is the entire sky.

    As a side-bar, what I found more interesting with long exposures on the P45+ was the fact that stars rendered their actual color more intensely than I'd ever seen with similar film captures.
    Jack
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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Quote Originally Posted by Jack Flesher View Post
    I can tell you it is a "noisy" image by any conventional measure. In fact, it is a good argument to stick to base ISO with these backs when doing long exposures.
    jack - could you say something about noise in the range of 1-5 minutes? what about dynamic range?

    --chris

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Quote Originally Posted by cly View Post
    jack - could you say something about noise in the range of 1-5 minutes? what about dynamic range?

    --chris
    I never really did very many shots in that range. Most of my "long exposure" frames were 15 or 30 seconds. I can tell you there that at ISO 50 they were exceptionally clean, though still visibly noisier than sub 1 second shots.

    Here's a 30 second, ISO 50, P45+ capture:



    Here is a 100% crop from the above frame, C1 NR set to 0/40/0 (Lum/color/long exp):

    Jack
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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    thanks a lot! may i ask to also post a crop of the lower left corner?

    -- chris

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Quote Originally Posted by cly View Post
    thanks a lot! may i ask to also post a crop of the lower left corner?

    -- chris
    Here you go:

    Jack
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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    What a forum! Where else can you order up crops from an image and have them delivered within an hour? :-)

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    once more: thanks a lot, jack!

    Quote Originally Posted by Audii-Dudii View Post
    What a forum! Where else can you order up crops from an image and have them delivered within an hour? :-)
    and not only that, it's one of the, pretty rare, friendly places in the web :-)

    compliments to jack and guy and everyone participating for keeping this a place where most discussions don't end in useless verbal fights!

    --chris

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Doug,
    Out of curiosity,if one does a twenty minute exposure, for example, does
    the black frame exposure process also contribute heat or can it be considered
    part of the cool down cycle

    Mark

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Quote Originally Posted by mtomalty View Post
    Doug,
    Out of curiosity,if one does a twenty minute exposure, for example, does
    the black frame exposure process also contribute heat or can it be considered
    part of the cool down cycle

    Mark
    Mark

    The chip is powered and is exposing even though there is no light hitting the sensor. So yes, it does create heat and noise and is not a part of the cool down process.

    Sincerely,

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Hi, I just wondered if someone could please let me know what "black frame exposure process" means. I would like to transition from MF film to digital and am considering purchasing a p30+ or p45+ back for long exposure work. I have never heard this term before though.

    Oh, and great information here, thank you!

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    black frame exposure process:

    Here's a brief summary, although there's more to it than just this:

    After the shot has been taken a second exposure is made by the back - the dark frame - which has no light hitting the sensor but the noise signature of the back is recorded. This 'exposure' takes the same amount of time as the original shot since you need to let the heat/signal noise build up. This dark frame is then processed against the original image to remove/reduce this background noise from the shot.
    Remember: adventure before dementia!

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Very interesting. Is this something you do manually? Is there an automatic feature for this with Phase One backs? Is it something you would do only for long exposures, or in general?

    Thanks.

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    The back will do it automatically. It means that when shooting long exposures that you need to figure that each shot will take 2x as long, once for the original scene capture and then the same amount of time again while you patiently wait for your MFDB to do the dark frame and processing. Obviously when it's doing this you can't shoot another image until it has finished.

    Some camera systems allow you to override this and not capture the dark frame and do noise reduction later in post processing. Phase backs, at least the ones I have, don't allow you to do this.
    Remember: adventure before dementia!

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Thanks Graham.

    Is there a difference in quality doing it in the back vs. doing it in post? Presumably the back is applying algorithms that clone the data around 'noisy' pixels the same as the computer software would do, so I am wondering which would do a better job, if there even is a difference.

    I shoot a lot of [upwards of] 10-minute shots in the daytime using a 10-stop ND filter, using various medium format film stocks. I have noticed that even the drum scans that come back from the lab have quite a lot of grain. I am hoping that getting into a digital back will yield more impressive results. Does anyone here have any advice/experience in this particular issue with shooting long exposure on film vs. digital? Perhaps this should be a new topic of discussion, but I figured I would ask!

  43. #43
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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Quote Originally Posted by Jack View Post
    Here's a 30 second, ISO 50, P45+ capture:

    Jack, this image is beautiful, thanks for sharing. Where is this location?
    Likes 1 Member(s) liked this post

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Sonar, are you compensating for reciprocity law failure with your film? If not, you are underexposing and contrast increases by the loss of shadow density. This could give you more grain.

    Digital does not suffer from reciprocity both with the exposure time nor change in contrast. But noise will build up. Some things you can do when you shoot, use ISO effectively and dark frame subtraction, some can be done in post, stacking several shots to reduce random noise. Since digital is more sensitive to IR, the quality of the ND filter is important for long exposure daylight work--if it does not cut IR, you will end up with a color headache.

  45. #45
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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    I generally expose about 20% longer than what the light meter tells me at a 10-stop increase, but I don't have a formula for compensating for reciprocity. Is there a general rule of thumb I should know about?

    Interesting what you say about IR showing up in the digital. This could explain something that has been perplexing me for some time. When I shoot long exposure in the daytime with a 5DMK2 I often get this distinct line in the lower 1/3 of the frame where the color values are significantly different. I can't explain it, it doesn't seem to matter what brand ND filters I am using (Lee, B+W, etc). I never considered that it could be infrared so I've not tried using a UV filter to see if that corrects the issue. I figured it was a limitation with the Canon itself. I have two 5D's and the issue occurs with both. I have not noticed this with film yet, but I have noticed that with slide film I get a strange redness at times over the entire image- which could be the same issue just expressed differently in the film.

    Here are two of the most apparent examples I got with the 5D earlier this year. The first image I stacked many ND filters on the lens to experiment bringing out this effect, and the second image just had one ND.




    Here is an image shot on film where the same phenomenon might be occurring, but is not as apparent (notice the lower rock cropping has red in it):



    Do you think the use of a UV filter would correct this issue?

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Hi Sonar,

    I wanted to pitch in one WHY a dark frame is done.

    When dealing with mathematical reduction of noise in an image (or music, or any other electronic recording) the type of noise is just as important as the amount. Specifically, if the software knows what the type of noise is in an image it can much more effectively reduce the noise in that image without significant loss of detail.

    For instance software has a much harder time removing "white noise" from an audio recording than removing a single constant tone (e.g. a buzzing noise).

    The "dark frame" is the digital back taking a measurement of both the amount, and the type, of noise being caused by the long exposure. By taking a 1 minute image and then a 1 minute blackframe the software is given a lot of additional information to work with and can do a very good job of providing you a final clean image.

    Notably for a Phase One digital back this extra information is only read by Capture One (due to extensive cooperation, co-development, and mutual interests of the software and hardware teams at Phase One).

    There remains no digital back in the world in the same league as a P45+ with current firmware for anything in the many minutes and above category.

    If you'd like to work with a Phase One partner with extensive long exposure experience we'd be honored to help; we frequently work with photographers on evaluation rentals which can be counted towards purchase :-).

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Quote Originally Posted by sonar View Post
    Thanks Graham.

    Is there a difference in quality doing it in the back vs. doing it in post? Presumably the back is applying algorithms that clone the data around 'noisy' pixels the same as the computer software would do, so I am wondering which would do a better job, if there even is a difference.
    This is actually a very interesting question!

    I think that it partially depends on what you are shooting as to whether the in-back dark frame subtraction and noise reduction is 'better' than post processing techniques such as the image stacking or noise analysis & subtraction.

    I'm no expert in this area but I do know that there are two types of noise that need to handled with long exposures - pattern noise and random noise.

    Pattern noise is best handled by dark frame subtraction, either in camera or it can be handled in specialized image processing software applications.

    Random noise can be tackled by shooting multiple images and then averaging them either in a tool like photoshop or better through a specialized image stacking application. Another technique is to shoot multiple short images and combine these in a stack which will in effect sum together the exposures - the benefit for noise reduction is that each shorter image may have less noise than the equivalent longer exposure image and so you'll combine these into a cleaner image.

    In in an ideal world, you'd get the very best results from a combination of dark frame subtraction & image stacking in one of the astrophotography applications since these can utilize algorithms that are more sophisticated than the in-camera processing of the raw file. However, at some point you have to be practical and that means with a MFDB like the Phase One P series, you are going to have the dark frame subtraction done in camera for you anyway. You don't have a choice. Then you have to decide whether you want to go through the hassle of processing a boat load of individual images to produce the equivalent long exposure. If you only have the ability to shoot at most up to 15-30s this may be your only option (other than film).

    I bought a P25+ specifically for long exposure work because it works well for my kind of shots of several minutes. I'd rather stack images from my IQ160 but the available software options to do this were somewhat limited and the ones I looked at wouldn't handle 60mp 16bit files well at all. If I'd hit the lottery then I'd have bought a P45+ because that's the king of long exposures with the higher resolution and longer image handling. If you ever want to use a technical camera you might want to avoid the P30+.

    One down side of using the P+ backs though is that you don't have the option to turn off the dark frame subtraction - not a problem on a single shot so much but if you want to shoot multiple images of a scene it would be nicer to be able to shoot ONE dark frame image and then multiple shots later at the same exposure settings. If you're shooting a 10 minute image then that saves you 10 minutes per exposure. Oh well, it is what it is.

    p.s. I'd take Doug up on his offer to have a chat ...
    Remember: adventure before dementia!

    As Oscar Wilde said, "my tastes are simple, I only like the best"

  48. #48
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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Quote Originally Posted by GrahamWelland View Post
    If you ever want to use a technical camera you might want to avoid the P30+...
    Graham, curious to know what you mean by this. I am seriously considering buying one of these right now, for both fashion work (which pays the bills) and long exposure work (which serves my soul).

    Is the P30+ the only back that doesn't have the option to turn off dark frame subtraction?

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    The micro lenses on the P30+ make it unsuitable for use with technical cameras (Arca, Alpa, Cambo etc) where you may have lens movements. You'll get horrible lens brightness and color casts on the this back.

    If you intend to shoot using a DSLR body you'll have no problems at all. It's not a bad back in any way, it's just not suited to technical cameras with movements. For everything else it has a great reputation.

    You might find this helpful: http://forum.getdpi.com/forum/showthread.php?t=15269
    Remember: adventure before dementia!

    As Oscar Wilde said, "my tastes are simple, I only like the best"

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    Re: How different are the P45+ and P30+ as regards long exposures and noise levels?

    Quote Originally Posted by sonar View Post
    I generally expose about 20% longer than what the light meter tells me at a 10-stop increase, but I don't have a formula for compensating for reciprocity. Is there a general rule of thumb I should know about?

    Interesting what you say about IR showing up in the digital. This could explain something that has been perplexing me for some time. When I shoot long exposure in the daytime with a 5DMK2 I often get this distinct line in the lower 1/3 of the frame where the color values are significantly different. I can't explain it, it doesn't seem to matter what brand ND filters I am using (Lee, B+W, etc). I never considered that it could be infrared so I've not tried using a UV filter to see if that corrects the issue. I figured it was a limitation with the Canon itself. I have two 5D's and the issue occurs with both. I have not noticed this with film yet, but I have noticed that with slide film I get a strange redness at times over the entire image- which could be the same issue just expressed differently in the film.

    Here are two of the most apparent examples I got with the 5D earlier this year. The first image I stacked many ND filters on the lens to experiment bringing out this effect, and the second image just had one ND.




    Here is an image shot on film where the same phenomenon might be occurring, but is not as apparent (notice the lower rock cropping has red in it):



    Do you think the use of a UV filter would correct this issue?
    That looks like viewfinder light leak. A very small amount of light leaks through the viewfinder and will cause issues during extremely long exposures, especially when there is a bright source of light behind the camera (e.g. sunlight). Just place a piece of black tape over the viewfinder.

    P.S. I do not claim expertise on film. However you can find emulsion-specific reciprocity failure (which includes both color and density shifts) on the film box itself, or, failing that, you can google "reciprocity [name of film]". It varies a lot between types of film (e-6, color neg, black and white) and a little between specific emulsions of that type of film.

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