Interesting MF digital article over at LuLa from Mark Dubovoy

[PeterA]

Re calibrating arTec: the Artec is a different animal to Alpa. What I like about the arTec is what I don't like about the Alpa 12 system. The artec gives me a focusing screen (via sliding system) and tilt shift. So 'calibrating a back to a fixed mount' is not an issue with artec - since you have a focussing screen to see exact focus.

What I dont like about arTec is what I liek about Alpa - with a 12 series you can shoot hand held in appropriate light conditions. Whilst arTec is tripod mount system - always.

Different systems with significant overlaping functionalities with some not overlapping functionality - Alpa/Arca/Artec are all extremely capable systems.IF you wanted a tripod system I would rate artec highest followed by arca and then Alpa - difference being the movement capbilities combined with in built focussing screen system tilts towards artec for a tripod system. Hwever on price vs functionality - probably arca wins easilly.

 

[D&A]

Yeah, really long, fast aperture AF lenses are the domain of the 35mm DSLRs for sure, I've max'ed out at 300mm on the H system and 350/4 on the Contax 645 before that. The HC300/4.5 takes the 1.7X teleconverter for a 510/7.6, but you lose AF. I don't use long glass much ... 180mm is about all I ever need even on a MFD.

-Marc

Thank you ever so much for your thoughtful feedback Marc. For general work, 180mm on MF is more than sufficient and often shorter focal lengths are required. There are two areas though that an equivelent of 250-300mm preferably with AF (focal length in 35mm terms) is required, without resorting to cropping the S2 file. One is for concert work, especially in certain venues. The other area is for wildlife although this can be approached with manual focus (and hopefully with even longer focal length lenses than stated above). Thus a 3rd party lens on the S2 would possibly satisfy the requirement for wildlife. Definitely food for thought. Thanks again!

Dave (D&A)

 

[Anders_HK]

From the calibration process you will figure out how much you need to move the focus helicoid (from the precise measured distance) to get good focus. This "correction" can be dialed in each time you focus with any lens.

Terry,

This assumes that the sensor is perfect parallel to lens plane, does it not?

Or is there a way to calibrate also to make perfect parallel?


Dear All,

Any info on shimmed/calibration of back from Cambo RS users?

What about how well the lenses are shimmed/calibrated to the camera system?


Thank you.

Regards
Anders

 

[ustein]

I enjoyed it.
Sad to discover that all the pictures I've taken in the last ten years aren't really up to it (35mm sensor). But I'll struggle on manfully.

I formated all my disks and kept my 5 P65 photos :deadhorse:

Looking for a new job now.

 

[Jeffg53]

I formated all my disks and kept my 5 P65 photos :deadhorse:

Looking for a new job now.

You could apply over at LuLa but your ego is a bit wimpy for there:cussing:

 

[aweitz]

Without going into every bit of detail, you can calibrate the Arca yourself by going through a process similar to what was posted about how they shim the Alpa. From the calibration process you will figure out how much you need to move the focus helicoid (from the precise measured distance) to get good focus. This "correction" can be dialed in each time you focus with any lens.

The issue is this: You can't simply dial in the correction if the sensor placement is skewed. If it's skewed by a fraction of a mm, then the Arca way is useless. You have to be able to shim from side to side up and down - and sometimes you have to cut the shim so that one side gets more of a shim. Alpa's way of doing it seems to be the most painless, in that you shim once for each back/sensor and then forget it.

Anders

 

[ustein]

You could apply over at LuLa but your ego is a bit wimpy for there:cussing:

I know, I know

 

[doug]

... wildlife although this can be approached with manual focus (and hopefully with even longer focal length lenses than stated above). Thus a 3rd party lens on the S2 would possibly satisfy the requirement for wildlife.

If you end up going this route I'd be very interested in hearing of your experience.

 

[etrump]

Comments on ego aside, I thought the whole benefit of lula WAS the one sided equipment rants.

Pretty typical for that site but I still find them useful and wasn't too offended when I read the article mentioned. He does make a valliant effort to explain it is just HIS opinion.

Anyway, aren't all digital mf'ers supposed to trash film and 35mm digital? I understood that was part of the mf creed. :ROTFL:

 

[D&A]

If you end up going this route I'd be very interested in hearing of your experience.

Hi Doug,

I am quite familar with many your fabulous images, having seen them posted here (on Getdpi) and also your interest and use in long lenses, for what you photograph. I had already had it in mind to contact you with any developments in regards to this (long lenses on the S2) if and when I decided to head down that route. So far, all consideration accomplished so far is unfortunately on paper. Having equipment in hand is really the only way to know what works and what doesn't...which in turn can end up being an expensive proposition. Of course this last point is all moot, if I win the lottery tomorrow Thanks!

Dave (D&A)

 

[Terry]

Hi Doug,

Of course this last point is all moot, if I win the lottery tomorrow

Dave (D&A)

Sounds like a good thread...."if you won the lottery, describe your new kit"...

 

[D&A]

Sounds like a good thread...."if you won the lottery, describe your new kit"...

LOL Terry...and along with describing the new kit, they should also mention all the locations they plan on going to with it

Dave (D&A)

 

[Christopher]

I think it is far more important to be able to actually focus exactly than to shim it. Sure if you have q back which is completely out of line you need to do something but, I know both my P65 and old P45 are good enough, so that I dont see any problems. However I can see a huge difference between the focus of 22 or 28 meters. Especially at f5,6 or 8

 

[thomas]

I think it is far more important to be able to actually focus exactly than to shim it. Sure if you have q back which is completely out of line you need to do something but, I know both my P65 and old P45 are good enough, so that I dont see any problems. However I can see a huge difference between the focus of 22 or 28 meters. Especially at f5,6 or 8

100% agreed!
if you look at the resolution of Alpa's new "high precision focus rings" you will find the indications will do for most purposes...

... however the much higher resolution of Arca's focus ring is certainly an advantage re the handling.
Also re even higher precission (if required).

 

[Anders_HK]

Well... lets define there is depth of focus which is between sensor and lens, and that DOF and focus point occurs on other end of lens...

Thus for wide angle lens depth of focus is way small (it is larger for longer lens), thus is that reason to shim back also for perfect parallel, as well as correct depth of focus?? Simply because depth of focus for wide angle is so very small, thus any error on it will make impact.

Correct?

Thus, is it possible to shim this on also Cambo and Arca?

Regards
Anders

 

[thomas]

Well... lets define there is depth of focus which is between sensor and lens, and that DOF and focus point occurs on other end of lens...

Thus for wide angle lens depth of focus is way small (it is larger for longer lens), thus is that reason to shim back also for perfect parallel, as well as correct depth of focus?? Simply because depth of focus for wide angle is so very small, thus any error on it will make impact.

Correct?

yes, correct!

Thus, is it possible to shim this on also Cambo and Arca?

on the Arca you don't have to. The focus indication on the Arca is linear and it doesn't show the distance in meters (or feet)... it does show certain numeric values that translate to a certain distance (they provide tables for each lens to translate distances into the respective values). So once you know the deviation of lens & sensor (let's say it's for instance 3 numeric values) you can use that offset for any lens at any distance.
So you don't shim the back... you actually just "shift" the numeric values on your tables

On other tech cameras you can adjust the lenses. I've once outlined how you can do it here: http://forum.getdpi.com/forum/showpost.php?p=240696&postcount=4572
You'll have to see if the outcome is still appropriate for focussing on the groundglass (if you use the groundglass for focussing at all...). On my kit the groundglass is still accurate for focussing.
But if the lenses require large adjustments the groundglass might be off. In this case you would also have to re-adjust the groundglass (for instance with shims).
So on an Arca or Alpa it's much easier to achieve the required spacing of lens + sensor. However, basically it's also possible to gain the same accuracy on other cameras.

 

[Anders_HK]

yes, correct!

on the Arca you don't have to. The focus indication on the Arca is linear and it doesn't show the distance in meters (or feet)... it does show certain numeric values that translate to a certain distance (they provide tables for each lens to translate distances into the respective values). So once you know the deviation of lens & sensor (let's say it's for instance 3 numeric values) you can use that offset for any lens at any distance.
So you don't shim the back... you actually just "shift" the numeric values on your tables

On other tech cameras you can adjust the lenses. I've once outlined how you can do it here: http://forum.getdpi.com/forum/showpost.php?p=240696&postcount=4572
You'll have to see if the outcome is still appropriate for focussing on the groundglass (if you use the groundglass for focussing at all...). On my kit the groundglass is still accurate for focussing.
But if the lenses require large adjustments the groundglass might be off. In this case you would also have to re-adjust the groundglass (for instance with shims).
So on an Arca or Alpa it's much easier to achieve the required spacing of lens + sensor. However, basically it's also possible to gain the same accuracy on other cameras.

Thanks

Thus is it correct to say that Alpa would be the only for which it would be possible to shim the back for sensor to be perfect parallel to the camera, and the Alpa camera is from factory at such strict tolerance as to say it is perfect parallel to lens plane (or each lens actually perfect from factory and by Schneider/Rodenstock calibrated as to be perfect parallel to camera)? And for all others it would take to shim each lens to achieve same?

However... on the others (Arca, Cambo etc), when turn the back 90 degrees... shimming would thus no longer be perfect correct, right?

Regards
Anders

 

[Guy Mancuso]

Comments on ego aside, I thought the whole benefit of lula WAS the one sided equipment rants.

Pretty typical for that site but I still find them useful and wasn't too offended when I read the article mentioned. He does make a valliant effort to explain it is just HIS opinion.

Anyway, aren't all digital mf'ers supposed to trash film and 35mm digital? I understood that was part of the mf creed. :ROTFL:

Bingo I think you hit the nail on the head here. LOL
I'm still laughing .

Luckily I actually have REAL clients that are extremely happy with me delivering these very high resolution images to them. At this point it is a demand they know what I am showing up with at the door going to there shoots and I am getting more work because of it in certain ways. These are corporate clients that have 5 shooters they use frequently. I know it is not just my gear but me as the shooter but it gives me a edge on the competition. This is real and not some fantasy crap that we often read.

Case in point and I even hate to admit this but stupidly I lost ALL my final outputs to clients on my Drobo. I accidentally formatted the Drobo. Now i always had the Raws on backup disks but the final image drive was also screwed. This is not pleasant to admit but I had all client delivered images on DVD as well and I always made a backup DVD. I have yet to fully recover from this and 2 weeks ago my website went down as the hosting company went belly up or something. So now I am forced to go through hundreds and I mean hundreds of DVD and recover the Final Tif images to get images back to use for the web site but also doing double duty to get these images back on the Drobo. I am cherry picking and already have 70 gbs back up on the Drobo and going through hundreds of images throughout the years with different gear. My point is here is i can see the differences between the cams that i shot. It is not much of a stretch to see what was shot on MF when comparing it to the quality of others and yes my processing has certainly gotten to expert levels for sure as we all learn over the years. My point is sure these MF images are very very good and for me clients are wanting it. I have very smart clients that see and understand the increase in the images.

But my Sony is damn good too for certain jobs so it all comes down to what needs you have . I don't have to prove the MF is a better file than 35mm and why should I . My clients are happy I am happy why argue with that. I honestly read some threads and say to myself WHY go through all this crap when most of these folks never even shot a MF system in there life. I am not saying MF is the king of the road and going to run everyone off it either. End of day who cares. All I care about is delivering the best that i can to the best of my gears abilities and mine. Its not about the gear it is about the image and that gets so lost in so many threads. Okay back to more DVD's and please remind me occasionally how much I hate DVD's and how smart I am to stay away from the holy wars.

 

[thomas]

Thus is it correct to say that Alpa would be the only for which it would be possible to shim the back for sensor to be perfect parallel to the camera, and the Alpa camera is from factory at such strict tolerance as to say it is perfect parallel to lens plane (or each lens actually perfect from factory and by Schneider/Rodenstock calibrated as to be perfect parallel to camera)? And for all others it would take to shim each lens to achieve same? However... on the others (Arca, Cambo etc), when turn the back 90 degrees... shimming would thus no longer be perfect correct (because back mount not shimmed to be perfect to sensor, only lens is for horizontal position of back), right, or?

okay, you are referring to the perpendicular alignment of the entire rear standard (and camera interface), not only to the lens-sensor distance... I didn't get you right, sorry.

Nope... Alpa and Arca have a different approach but basically can achieve the same accuracy. On both you can't adjust the perpendicular alignement - only the lens-sensor distance. I've outlined above how you can achieve the same on other cameras... but again only for the lens-sensor distance.

I have to say that the parallelism on my Cambo WRS is dead on. You can easily check the alignment of camera & sensor if you use large movements and check focus at infinity and then turn the digiback 180° and shoot at the same large movements. If the outcome is the same (i.e. if the spread of sharpness is the same...) the kit works as supposed to. If not... it could also be the sensor that is tilted (or the lens).
I certainly think that Alpa cameras are exceptionally made... no doubt about that! I just don't have any accuracy issues with my WRS... therefore I have no reason to trash my kit and buy an Alpa. I would take an Rm3D anyway if I'd switch the platform one day. Personal preference...

 

[Mike M]

thanks for all the info about focus accuracy...shimming and work arounds between the various camera makers

This is great stuff to be aware of...thanks everybody