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Cambo owners - shimming the back

jagsiva

Active member
As I go through my options for a tech cam, the cambo WRS keeps drawing me in as a great balance of size with movements. The other option is the RM3Di, but it is a little bigger and the has 10mm less movement left to right. I could flip it, but that is another work around.

One major question I have is whether the Cambo can be shimmed. The Arca and Apla offer what appears to be a very precise mechanism for doing this. I have read on this board and process for adjusting 4 screws on the Cambo to achieve the same. Has anyone tried this and is it as "idiot proof" (important in my context) as the mechanisms in the other two? Are the results comparable?

I will be using it with an IQ180. Thanks for any help and thoughts.
 

Guy Mancuso

Administrator, Instructor
You can shim the body. I never did it but I did calibrate some lenses which for me was easy as I shot tethered and set my infinity deadly right on the mark. One of the Cambo reps can speak more about the body but I found no need. I did adjust the plate so my back fit more tightly to it. Also our dealers here can probably do this for you as we'll.
 

jagsiva

Active member
Thanks Guy. You were one of the people I was hoping would comment.

When you say you adjusted the plate for a better fit, was this just manipulating the plate or something more by design to allow you to do this?
 

jagsiva

Active member
Thanks Peter. I did not realize you could adjust the lenses this easily. This does appear make equalize the whole shimming issue for the Cambo.

Thank again.
 

Guy Mancuso

Administrator, Instructor
Yes it works really well the adapter plate has actual washers in it that you can remove and adjust your back. That's the first thing to do. Than tether your laptop and see if the infinity mark is dead on . If not than adjust lenses my 35xl was really off my 60 was perfect and 90 very slightly.
 

Don Libby

Well-known member
I've been using the WRS for longer than I can remember and just never felt the need to shim the body. Still don't.

Don
 

Anders_HK

Member
I've been using the WRS for longer than I can remember and just never felt the need to shim the body. Still don't.
Don,

As someone who have been looking into tach cam for awhile, I wonder if you have tested your WRS to ensure of its focus accuracy?

Best regards,
Anders
 

Anders_HK

Member
If I understand the differences between Cambo, Alpa and Arca;

1. Alpa is the only one who permit shimming of the back to a camera system , which (assumably) is calibrated to within tolerances. The advantage is that groundglass likewise is (assumably) calibrated from factory to that system, and that one can use someone elses lens which will be equally sharp due within tolerance to the system.

Likewise Alpa is the only one who have their lenses calibrated/adjusted by Schneider and Rodenstock.

2. Cambo permits calibration of lenses by user. That makes the lenses match any tolerance in location of sensor in digital back. However, downside appear to be the groundglass not being calibrated to the sensor in back and thus that it is rather useless to arrive at perfect sharp focus (unless if with luck the groundglass from factory match the sensor plane perfect)? Likewise, if borrowing a lens from someone it will likely not match the camera system or sensor.

Then, what is frank point of shimming the back of a Cambo?? Or rather, how can one calibrate/shim the groundglass plane to be in perfect with the sensor plane?

3. Arca permit for table look up of offset factors to account for tolerance in digital back. Then same as Cambo the groundglass will not be in tolerence for focus accuracy??

Am I understanding the above correct?

Please do not get me wrong. I have been looking at Alpa for quite awhile but find indeed the Cambo RS400 and RS5000 very interesting alternatives. Getting tolerances perfect for Cambo though seem somewhat an issue if one wants to be able to have the option to also use groundglass for precise focus. Additionally, the fact that Alpa sends lenses to Schneider and Rodenstock is assuring.

Appreciate any insight from users!

Thanks!!!

Best regards,
Anders
 

dougpeterson

Workshop Member
Frankly I find the ground glass to be "useless to arrive at perfect sharp focus" anyway. At least when talking about focusing exactly the detail from an 80mp image (that can be easily printed a meter wide) on a 645 sized ground glass. Even with a good brightscreen and a great loupe and patience it's not for the feint of heart.

Anyway, keep in mind that "shimming" is a really fancy word for putting a piece of thin metal sheet between two components. So just about anything that can be removed from a system (easily, or by means of disassembly) can be shimmed if it's really important to you.
 

Guy Mancuso

Administrator, Instructor
I'm with Doug on the ground glass use. It's a kludge to even use it and many folks don't bother. I never found the need myself. Also you have some marketing going on here. If your focus is dead on with your back than shimming will do nothing for you. All it really does is get you align with a graphically number like 10 ft for example well there is play in any lens and the markings for 10 ft could actually be 11 ft. Yes even with the nice focus rings that Alpa uses it still can be off. Arca has offsets which work really nice but with Cambo calibrating your lenses works just as well. End of day all you care about is nailing focus any IQ back will tell you that in a second with focus mask or 100 percent zoom , really who cares if the graphical number is off. In effect all three systems do exactly the same thing they just do it differently. I never had a issue once I calibrated my lenses. Also if you set it up for the ground glass than even they have play in them. BTW you can shim a Cambo body I just don't know anyone that has even bothered when its easy to calibrate a lens to a so called numerical number. That's all any of them do anyway.
 

jagsiva

Active member
In my case, GG is out of the question. As Doug mentions, at least for me, it does not offer the level of resolution to justify all the troubles of going to a tech camera, i.e., I will not realise the full value of the "hypothetical" quality of the IQ180 and tech lenses.

For this reason, I will likely rely on a rangefinder and/or live view. So precision of the GG vs. compensated for lenses is not an issue.

More of an issue of course is ability to focus accurately. I am still pondering this one.
 

Don Libby

Well-known member
I tried using a ground glass for almost a year and found it all but useless for what I do. While it did offer "some" benefits they simply weren't worth the it. Stoped using it and sold it shortly afterwards. I'm now shooting with a IQ160 attached and have so far found that to be one of if not the very best back I've had the pleasure using (started out with a P45+ then P65). The IQ series is made for a tech camera.

Don
 

Anders_HK

Member
Well, if there were no accuracy in using a goundglass there would be no possibility for arriving sharp focus using an 80MP back on a Techno or with any sliding adapter, right? Unless tethered or live view...

On a Cambo with lens movements, then how would you focus accurate without shooting tethered or live view? That seems when a groundglass would be needed, or??? Say e.g. you have three redwood trees that you want to compose for them to be in sharpest DOF but they are lined up at 45 degree to camera? Is not that a case for when an accurate shimmed groundglass would be necessary?

Thanks!

Best regards,
Anders
 

Guy Mancuso

Administrator, Instructor
Honest answer its all guess work unless you have live view or focus mask to confirm it. Ground glass on tech cams is nothing like a 4x5 its very hard. You can certainly do it but I bet your still going to want to confirm it after you took the shot. Just not so sure you want to rely on it solely unless your doing studio work and a lot easier to deal with it but there you have tethered.
 

Don Libby

Well-known member
Totally agree with Guy on this one. I tried the ground glass route for focus and quickly found it all but useless (FOR ME). Others may find it better. The best use I found the groundglass for was using a filter. This of course was before the IQ came along.

Anders - to answer you question - no I've never really tested my WRS as I've simply never felt the need. That said, of course I suppose it couldn't hurt.

Don
 

MGrayson

Subscriber and Workshop Member
On a Cambo with lens movements, then how would you focus accurate without shooting tethered or live view? That seems when a groundglass would be needed, or??? Say e.g. you have three redwood trees that you want to compose for them to be in sharpest DOF but they are lined up at 45 degree to camera? Is not that a case for when an accurate shimmed groundglass would be necessary?
Anders,

The answer to your question is iteration. You take many shots to get the focus correct, making small adjustments of focus and tilt/swing each time, and examining the effect with focus mask or 100% zoom. This is very different from GG focusing, but works extremely well. With large memory cards and a fast back, it is a quick and relatively painless exercise.

The attached file shows two shots from such a focus/compose sequence. The bright green is the Focus Mask, not the foliage! The extra green in the foreground of the second frame is the Focus Mask indicating improvement.

Best,

Matt
 

Guy Mancuso

Administrator, Instructor
And really if you get right down to it. It's very much like shooting Polaroids but much quicker. I think and work with tech cams in that fashion. No matter how perfect the camera setup is you still wind up confirming every shot but that comes after the shot really either by focus mask, 100 percent zooming and such. Live view as we know with MF is no Nikon or Canon setup until these sensors become CMOS than things will change.
 

Anders_HK

Member
The answer to your question is iteration. You take many shots to get the focus correct, making small adjustments of focus and tilt/swing each time, and examining the effect with focus mask or 100% zoom.
Above seem tedious as compared to using GG focusing. Joe Cornish write of using IQ180 on Techno (from IQ180 - First Three Months - Impressions - On LandscapeOn Landscape)

"... I am getting such great results with the Techno and the sliding back (and my Silvestri 10x loupe)"

"I make no bones about, 5×4 wins by a mile for viewing. But, once accepted and persevered with I have found my ability to compose upside down on a ground glass screen at this size is perfectly possible. I often use a Hasselblad ‘top’ viewer, which has a 3x magnifier and shows the whole screen. I finish the process with a Silvestri 10x loupe, and this gives me reasonable security that I have done any tilt adjustments correctly. In practice, setting up a Techno and a medium format back actually takes me a little bit more time and trouble than a 5x4inch Ebony. Of course all the preceding comments would apply to any technical view camera used with this format and not just the Techno."


The use of a 10x or 6x may also depend on the GG used. A Maxwell GG has been said to be brighter than Cambo, Alpa and Arca GG, and I would assume also the Linhof. Thus perhaps a 6x Rodenstock Aspheric Loupe would suffice using a bright Maxwell GG ???

However, the GG need to be perfect (within a tolerance) in plane with the sensor in the digital back. With Alpa that seem not a problem since the back is shimmed to the camera system. However, does Cambo offer any means to adjust the GG to the senor in back, or how would you shim the back interface to be perfect in plane to the GG???

Anyone with experience?

Thanks!

Best regards,
Anders
 

jlm

Workshop Member
you can, using screw adjustments, effectively "shim" the cambo, but you are basically using the images created as a measure of success, and the lens is set at infinity.
n not sure if alpa offers a different solution, using metal shims rather than screw adjustment
 
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