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Phase / Leaf mount or sensor misalignment?

tjv

Active member
I have a Leaf Credo 60 in V mount. Without getting into too much detail, I started experiencing focusing errors and at first blamed my Linhof sliding back - two left / right frames to stitch consistently showed front and back focus respectively. Turned out not to be the case as another slider yielded same results with all the same lenses and camera etc.

Long story short, I thought to check the V adaptor plate by rotating it on the back in the slider and morning the back on the adaptor in both horizontal and vertical positions.

Without applying abnormal force to clip it in to the top V mount latches in portrait orientation, the point where the latches hook into the back made a disturbing ‘crack’ and the back is now completely stuck on the plate. No amount of force I’d be comfortable using can get it off… so perhaps this suggests the root of my left / right focus shift issues...

The back and / or plate is stuffed - well at least if that wasn’t the case before it certainly is now! At the very least I now have to send the back to Phase / Leaf to detach the plate and fix the mount plus check for sensor and mount alignment. I have no idea how a problem like this could suddenly arise. Baffling... any ideas?

Anyone out there had anything like this suddenly happen to their back, sensor and / or mount slipping out of alignment without any knock or warning?

Any idea what a service charge for the above runs for? I live in New Zealand so that does complicate things somewhat as we have no dealer network worth anything here. My back was purchased new here, but I am the second owner and have had it without problems for five years.

Thanks,

T
 

alistairsimmons

Well-known member
If I were in your position I would speak with Rory at Specular in Australia and have him advise/send it to Phase One for estimate. The minimum service check charge of a digital back is €500 + shipping, but Specular would your closest/best contact to discuss it with, and get a solution.

Al
 

tjv

Active member
Thanks Al.

It seems crazy but it’d just as costly to send to Australia than to the US, EU or UK. It’s a real shame that the NZ representative is so hopeless. I guess the customer base is just not here, but then I wonder why they bother...

As an aside, we met last year when I was passing through London and I purchased a battery for my Credo. You have a great selection of gear on hand!

T
 

tjv

Active member
Ok... the back is totally fine. Phew! It was a weird anomaly on the adaptor plate and a trusted tech saw and rectified it straight away. Focus shift issues however seem to be to do with the sliding back after all... maybe Alpa is right after all...
 

Steve Hendrix

Well-known member
Ok... the back is totally fine. Phew! It was a weird anomaly on the adaptor plate and a trusted tech saw and rectified it straight away. Focus shift issues however seem to be to do with the sliding back after all... maybe Alpa is right after all...

The number of potential opportunities for tolerance fatigue with a digital back on a tech camera are many.

Start with the digital back, the sensor position, the face/connecting point of the digital back, the connection device itself, the interface plate, the rear face of the camera body, the connecting devices to attach the plate to the body, the depth between front and rear of the body, the front face of the camera body, the connection device for attaching the lens to the body, the rear of the lens mounting chassis, the optics in the lens, etc. This is not even a complete list.

It's amazing that these solutions produce the amazing results they do, considering the challenges.

Sliding backs bring their own set of elements to the equation, but even assuming your eyes are good, and the ground glass assembly is properly positioned, your results will likely be inconsistent at best (for true accuracy). I did a sliding back test one day with numerous sliding backs from multiple manufacturers. I found the best I could achieve where the focus point did not (noticeably) move after sliding the digital back over after focusing through the ground glass was 6 out of 10.


Steve Hendrix/CI
 

tjv

Active member
Thanks Steve,

I appreciate your reply and agree with your assessment of sliding backs. It does seem that while convenient they are problematic. I don't think I'm being unrealistic in my expectations for accuracy though, as this is what this equipment is marketed for. Otherwise why bother?

In any event I think I'll have to try another solution, maybe a direct adaptor to the camera. I'll lose my ability to stitch my much loved 1:2 panoramas, but at least I'll get consistent results (hopefully!)

All of this hassle makes me long for Alpa...

In your opinion, how accurate is the stitching mechanism on the Max and STC in regards to this stuff? Is there as much play in that as there is in a sliding back, seeing as they kind of offer the same functionality (minus the GG facility of course.)

Thanks,

Tim
 

dchew

Well-known member
Hi Tim,
The nice thing about the Alpa design is you really can test this because you can rotate the lens 90 degrees to see what affects the image sharpness: lens or mount(s).

I often go through an alignment test to verify things are square. It goes something like this:
  1. Shift the STC all the way, 18mm.
  2. Focus in the bottom corner.
  3. Take a series of 5 images, rotating the lens 90 degrees each time.
  4. Compare images. The 5th image is a “qc” check to make sure you didn’t bump anything during the process; it should look just like the first image.
  5. This part of the test shows any lens alignment issues at the far corners of the image circle. It’s a reference for the best you can get without bringing in camera alignment issues.
  6. Now, use Jim Kasson’s method of lens testing with the added step of shifting the back using the camera movement. Focus in a far corner when shifted, then shift the opposite direction and swing the camera to get the target in the opposite corner of the image circle.
  7. Again, compare the images. This reveals the difference between lens-only issues and camera system alignment issues.

My experience, with a sample population of 1 that is 9 years old, has been quite good and repeatable. I don’t notice any additional variance with the camera system; certainly nothing that compares with tiny changes in focus point. But, I’ve only been doing this for the last three years or so since getting the IQ3100 and now the 4150.

Dave
 

dougpeterson

Workshop Member
In your opinion, how accurate is the stitching mechanism on the Max and STC in regards to this stuff? Is there as much play in that as there is in a sliding back, seeing as they kind of offer the same functionality (minus the GG facility of course.)
I'm not Steve, but I hope you won't mind me pitching in my two cents.

There are two limitations on sliding GG on these systems: 1) they add several additional tolerance points that all accumulate 2) the ground glass itself and the sliding backs that house them were all designed in the era of much lower resolution backs.

I actually think #2 is more important as the tolerances and designs that worked very well at 16mp and 22mp are not well suited to use at 150mp. Current Phase One backs can make razor sharp 4 foot prints; try super-fine focusing that much detail using a ~2 inch ground glass. Ever since the advent of high quality live view, we have sold nearly zero sliding ground glass units.

Switching to the context of modern tech cameras my experience is stellar for all four major brands (Arca, Cambo, Alpa, Phase). It's just not something I think you need to worry about absent a specific reason (e.g. the camera was dropped and you're worried something has been effected). That said, if it helps provide you assurance, it's not unreasonable to ask your dealer to test the entire system prior to delivering it to you; that's the kind of value added service you should expect from a value-added partner!

On the new Phase One XT there is no separate adapter plate, which takes out one point of tolerance and the entire system (including back and all lenses) are tested as a unit by Phase One before shipping. I don't think that is necessary, as our experience has been great even on systems for which that is not true. But it can't hurt!
 

Steve Hendrix

Well-known member
Thanks Steve,

I appreciate your reply and agree with your assessment of sliding backs. It does seem that while convenient they are problematic. I don't think I'm being unrealistic in my expectations for accuracy though, as this is what this equipment is marketed for. Otherwise why bother?

In any event I think I'll have to try another solution, maybe a direct adaptor to the camera. I'll lose my ability to stitch my much loved 1:2 panoramas, but at least I'll get consistent results (hopefully!)

All of this hassle makes me long for Alpa...

In your opinion, how accurate is the stitching mechanism on the Max and STC in regards to this stuff? Is there as much play in that as there is in a sliding back, seeing as they kind of offer the same functionality (minus the GG facility of course.)

Thanks,

Tim

Hi Tim -

You don't have as much play with a geared drive on a tech cam as you would with a sliding back on a view camera. With the exception of the built-in geared sliding back of the Sinar Artec and the Cambo WRS 6000 tech cams, I'm not aware of any other sliding backs that offered geared movement. Instead, they slide on a rail, and that setup cannot be so tight and play-free so that the sliding mechanism won't be able to slide. Some sliding back models are tighter than others, and even the best may need a tune up.

Add that to the view camera component, which often has a tilting rear frame or standard, which must be secured by self locking gearing or manual locking gearing, and you have more potential for play. Try pressing against the top of your rear standard and you will see at least one potential point of weakness, but the sliding mechanism of the sliding back is another. The geared travel for the tech cameras does not have the limitation that a rail travel device would (assuming good health of the gearing).

The tech cam body itself also doesn't have the same potential give that a rear standard/frame would on a view camera. However, the tripod head at this point does introduce that potential, functioning similarly as a "rail" that the rear standard of the view camera would be attached to. The View Camera also has this potential issue to account for as well, in addition to the rear standard/frame itself.

There is also potential for movement (give) with the tech cam on top of a tripod head that is not really robust and locked down. But this is mitigated to a large degree by how you move the digital back. For most tech cameras, you are rotating a gearing knob with a finger, and not applying much forward/backward pressure to the camera. And in the case of Alpa tech cameras that optionally allow you to release the gearing and slide the digital back manually, the amount of travel is much less than the travel on a typical sliding back, and less travel means less opportunity for intolerance.

Importantly, any single issue can produce an intolerance factor, but the factor is magnified by the sum of all potential intolerance points. Most tech cam and view camera users are producing photography with precision, but if not, then it is good to know the potential points of weakness (things can generally be improved where there are problems). Recently we had a problem with some intolerance that we picked up in our tech camera pre-sales testing (If you order a tech camera lens, we are going to test it before shipping to you). Every component was good, the sensor position was good, the interface plate was measured and within tolerance on all 4 corners, same with the camera body, front and back, same with the lens mount. It turns out a latching mechanism needed adjustment. That's a good example of how precise (and accurate) these devices can be, but measuring the components in this case did not provide the clue to the issue. Real world testing of the entire system is best.

You're not using these systems because they are accurate and precise. You're using them because the quality of the individual components (the optics, the digital back, the functions of the camera body) allow you to produce unmatched results. The fact that you are creating this solution by manually connecting modular components creates challenges that stress tolerance factors, but in the vast majority of cases these challenges are overcome and precision is achieved.



Steve Hendrix/CI
 

Geoff

Well-known member
Forgive me Doug, Steve, and Tim for jumping in. A bit to add, from the side of shared user-experience.

Tim and I got to know each other through our shared use of the Linhof Techno and Credo 60 backs. The Techno has some good features, most notably is the ease of lens changes (uses Technika lens boards) combined with a very rigid rear standard. However, the front standard, with all the movements, is difficult to get absolutely perfectly aligned with the rear. This has been well-discussed elsewhere (see Anders Torger's extensive review of the Techno) and he points out its zero detents are too generous. There are ways to help this (use of fixed stops to set it up right) but these may not be enough for the 35mm lens.

If one adds a bit of sliding back misbehaviour, well, you can predict what would happen. And its quite likely that is what happened here.

There is a bit more to the story. Tim was interested in checking out the Schneider 35mm XL and I sent him mine to try. He got decent results in the center, and poor results off-center. The lens has since been checked for parallelism (front to back) by Precision Camera and is OK. I got better results, but it was still not perfect on one side. I suspect some mis-alignment somewhere.

Looking deeper, his Linhof stitching back had some issues; my Silvestri stitching back has done well for me, especially with other lenses. But maybe the 35mm needs really precise alignment and struggles in this setup.

Both Steve and Doug are right about the advantages of an Alpa (or Arca, Cambo) with fewer assembly combinations and tighter tolerances. That is quite clear. If one were to stay with a Techno, perhaps this could be used to set up absolute paralellism of all the faces, say by working off a building face....: https://www.bhphotovideo.com/c/product/157407-REG/Versalab_PARALLEL_Parallel_Alignment_Gauge.html

Or perhaps, the demands of that 35mm lens (and other wides) simply need a better platform.

All in all, then:

  1. less assemblies or combinations are better - less chance for intolerance
  2. pancake cameras have assuredly better alignments . But one has to buy into their lens mounts...
  3. parallelism of the standards is important.
  4. some combinations of lenses, f stops, print sizes, and back size (both sensor dimensions and resolution), may be more demanding; others may be more forgiving. Tim prints much larger than I do.

Which leaves the nagging question: how good do you need it? For a 150mp back, clearly the best everywhere.

There may be some other issue with this particular camera/setup yet to be unraveled. Maybe send it back to the mother ship to get calibrated?
 

dougpeterson

Workshop Member
Which leaves the nagging question: how good do you need it? For a 150mp back, clearly the best everywhere.
I'd personally revise this a bit to "For a 150mp back, if you want to hit its max possible res, clearly the best everywhere is desired".

The point being that many images/scenes/use-cases do not require maximum resolution, and in some cases the purpose of the image is actually inhibited by razor-sharp detail. If a given camera (whether the techno, a pinhole camera, an old wooden 4x5 or otherwise) helps you create the images you like to make and/or is enjoyable to use then it may forgivable (for some users and in some use cases) that it not perform with 100% maximum sharpness. Same goes for lenses or workflows.

It may be an assumption that everyone buying an IQ4 150mp wants every image to be as sharp and detailed as possible, and that's why they bought a 150mp camera. That is certainly true for many/most of our clients, but we have a certain subset of clients who are using 100mp or 150mp backs to create imagery that is abstract, or motion-blurred, or soft-focused, or using older lenses and therefore NOT dependent on maximizing resolution. There are many other reasons someone might have bought such a back for those use cases (color, dynamic range, ES, nearly zero color cast, tonality, best-ever IR if using the achromatic version etc etc).

But yes, if you're looking to create tack-sharp 150mp images you don't want to hamstring yourself with gear that isn't parallel unto itself; that really puts a wrench in the works!
 

tjv

Active member
Thanks guys,

I’ve been tied up with pre-Christmas duties today so I need to keep this quick...

I really appreciate the replies and thoughts on the matter.

Linhof & Studio, UK have sent me a Christmas care package containing a ton of parts to help diagnose the root cause of the problem.

A new V back adaptor
A direct camera-back adaptor to remove the sliding back altogether
A new sliding back plus GG set to compare to mine

I am absolutely blown away by their service, as usual. They have done all of this for free, including courier, as part of their long term customer support. I bought my Techno and lenses 8 years ago and digital adaptors etc 4 years ago, plus live all the way in NZ, so they’re entrusting me with a lot!

I will write a longer reply when I have a chance, just wanted to give a brief update as to where I’m at.

I must admit though, the draw to Alpa for the long term is strong but I really do love my Techno. I think it’s a terribly underrated setup, especially for people like me who still shoot a lot of film. I think with a CMOS back with live view I’d be in heaven, although that would definitely necessitate dropping the sliding back and forgoing stitching panoramas - for that I think a pancake camera would be better.

Maybe the replacement sliding back will prove me wrong...

T
 
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tjv

Active member
A brief update now that the components Linhof and Studio sent me have arrived and I have had time to do some testing...

Something is definitely out of whack, but I don't know where as things are so inconsistent.

To summarise...

Both sliding backs give different results, and focus position relative to GG AND actual point of focus changes depending on the back adaptor used AND position of the sliding back.

One slider shifts focus forward on the right shifted frame and slightly rear on the left, the other the opposite when using the same back adaptor plate.

With the other, new adaptor plate, my slider is WAY off and the loaner slider is near to my old slider with my plate.

The director adaptor with the new adaptor plate is way off – GG focus is drastically off the focus point on sensor to the point of being comical.

The loaner sliding back with my adaptor gave the best results by far when the back was in landscape orientation, but it noticeably shifts focus forward when shifted left – the opposite of with my adaptor plate.

(At this point of testing I was wanting to get drunk, and fast...)

So...

What the hell is going on here?!?! Could my back / sensor be out after all? Can that even happen? Seems like a possible combination of a few things, but the most consistent thing is the back and body – the problem happens with both of my lenses. The rear standard of the Techno is rock solid and even if the front standard were off, I'd have thought all other things being equal because I'm supposedly shifting the back perfectly parallel left and right, the focus point shouldn't shift...

Help! :banghead:
 

dchew

Well-known member
Tim,
You said, "The rear standard of the Techno is rock solid and even if the front standard were off, I'd have thought all other things being equal because I'm supposedly shifting the back perfectly parallel left and right, the focus point shouldn't shift..." I don't think that is correct. If your front standard has a bit of swing/tilt at the zero points, then shifting the back will show a big difference because you are out at the edge of the image circle where the front standard error is magnified.

I do think it is pretty normal to have different adapters with slightly different focus points, as well as different sliding backs. I have two Alpa back adapters and their shim stacks are definitely different. I have two 17mm adapter/spacers which are very slightly different. Not something I would notice at f/11, but when critically testing for the shimming process I can see a consistent difference.

Regardless, when I'm faced with these situations that make no sense I go back to the beginning and eliminate variables one by one.

Consistency: Focus on something, shoot, slide back to the GG but don't touch anything else. Slide back, shoot. Do it three times. Do they look the same?

Operator Error: As simple as things seem, you need to know how consistent you are. Focus, shoot. Scramble focus, focus, shoot. Do it three times. Do they all look the same?

Lens: I don't know the Lindhof. Can you rotate the lens in the standard or in its mount? If so, shoot, rotate it and shoot again. Do they look the same?

Adapter Plate: It looks like the direct camera-back adapter can be mounted any direction. If that is true, rotate it 180 degrees and take an image each time. Do they all look the same? Do it three times so the first and last are the same position. At least those two should look the same.

Field curvature: Without shifting, focus on something in the center. Is the edge out of focus? If you concentrate and focus on that part of the image, does it get sharper? Is the center now out of focus?

Sliding back: This gets tough because there are so many variables when sliding the back; that's why I left this for last. If all the above are consistent, then you can isolate it to the sliding back not being parallel.

I apologize if this is all basic an unhelpful. I used the Sinar with its sliding back for a while, but never the Techno so I am flying blind.

Dave
 

Geoff

Well-known member
Dave -
This is an excellent set of recommendations. Thank you for the outline, its good for all of us.

The Techno has basically a large fixed back which is cast solid with the bottom of the camera. It has a rise fall capability built in, but its quite recessed, geared and stable as a rock. And his issues are with shift. Its quite possible that its a combination of some front standard out of true (easily done) and some variance in the shifting back. And maybe the mounting plate isn't quite flat? Could that be rotated?

Other possible additions to your list:

- which lens, f stop, shutter speeds?
- which mount is your Credo? Did you change adapter plates when using new slider?
- what magnification are you using to check focus?
- try different lenses and changing the f stop

Geoff
 

tjv

Active member
I spent three hours today trying to get to the bottom of this. I tried my absolute best to work methodically, testing each component in different possible combinations with two different lenses stopped down to f11 and wide open. I keep getting these random, completely out of focus shots that I find hard to pin down to user error – I've seriously never noticed these user focus errors issues when working in the field, ever. I talking serious miss-focus. At least I've not noticed it before I suddenly observed large focus shifts between left / right frames for stitching several weeks ago.

I think I'm going crazy, so will put the whole lot away for a day or two then do it all again with renewed energy.

Thanks for the feedback.

Off for a beer...

Can someone answer for me though: Has anyone ever observed a sensor coming slightly loose in a digital back? Even a sensor that's gone out of alignment somehow?
 

Geoff

Well-known member
If I read you right, are you saying that sometimes a shot (and shifted ones too) will be just fine, and then other times there is serious misfocusing of the same shot setup, although all the other variables aren't changed? If so, that begins to limit the problem to a mechanical one, something like, as you suggest, either sensor shifting or something else moving.
 

tjv

Active member
Hi Geoff,

Yes, that does seem to be the case. I'm going to run one final test to confirm because I don't want to pay crazy money to send the kit to the EU only to be told it was a fault of the back all along, or even worse – well, it depends on how you look at it – that it was some stupid user error oversight...

Anyway, to answer other questions:

1: Adaptor plates:

Linhof & Studio have leant me a brand new one, so I have two in my possession. They are V mount.
Curiously, my adaptor plate is branded Phase One, and the other is a Linhof made product.
My plate is silver and seems to fit perfectly into the short slider, except for the fact the locking mechanism does not clip into the 'lock' position with it as the edge is slightly more raised / less bevelled. The Linhof plate is anodised black and of course locks in perfectly with the Linhof slider. However curiously, in tests so far, the Linhof plate seems to give the worst results in both sliders, being focus is more off. More testing needed...


2: Sliding backs:

I have the loan of a demo (i.e. used) Linhof short sliding back, plus my long sliding back.
My long slider actually has more depth to it, so that explains the problems I had getting infinity focus with your 35mm XL.
The short slider sits flush with the back of the camera and seems more solid, where as my long slider made of thinner metal and sits back about 1.5mm from the rear standard. The part where the back and GG sit when in taking or focusing position respectively is solid, but outside of that the slider is a bit flexible.


3: Direct mount and GG frame

I have the loan of a 1697 universal adaptor (https://www.linhofstudio.com/products/Linhof-cameras-Techno-Series/Universal_Adapter_for_RSC_Adapter_Plates_for_Live_Focus).The back adaptor plate fits into this, on which the back then connects.
To use the GG you need to remove the back AND the adaptor plate, then insert the GG frame (https://www.linhofstudio.com/products/Linhof-cameras-Techno-Series/Ground_Glass_Adapter) in the adaptor plate slot – The has the same shape connection, obviously. This is a real pain in the arse, as this means two things to connect and disconnect when swapping the GG for the back, and there's no 'cap' you can put over the adaptor plate when it's still connected to the back to save from constantly disconnecting both in order to protect the sensor.


4: Replacement GG and fresnel.

I have loan of a replacement set to test against mine. This I can categorically say gives the same results. As an aside, it's the standard GG and I think that while it's a lot darker it's actually slightly finer grain and may even be easier to find focus with...


Off to test again now. Wish me luck. If you see any mushroom sounds on the news emanating from New Zealand, you'll know it's me loosing my temper...


If I read you right, are you saying that sometimes a shot (and shifted ones too) will be just fine, and then other times there is serious misfocusing of the same shot setup, although all the other variables aren't changed? If so, that begins to limit the problem to a mechanical one, something like, as you suggest, either sensor shifting or something else moving.
 

tjv

Active member
To those who have been kind and interested enough to reply:

I have sent the entire kit minus the digital back to Linhof Studio for testing and service. I was finding the testing a real mind bending experience, so think this is the best option.

My gut feeling is that something is off, most likely the sliding back. Maybe also my adaptor plate.

For whatever reason the direct adaptor and gg frame I was leant gave wildly off results, but the two sliders relatively close results with mine being worse. It could simply be that sliding backs in general are sub-par for this kind of work, but I know for a fact my setup used to give perfect or at least close enough to perfect results. Now it’s quite a bit out when slid to the right - centre and left are pretty much identical.

Of note is the Linhof sliding back only has three positions, being centre and +/- 17mm L/R.

Anyway, a good service of the camera to check parallelism is due anyway and I’ll get the copal shutters tuned as well. If that doesn’t result in a cure or at least improvement I know that either my back is out of square or I need to consider an alternative setup.

Linhof Studio have been truly awesome to deal with and a great help in trying to find a cure through the loan of parts, and I know the kit is in good hands with them.

If it comes to needing to send the Credo 60 for service I may be in for a rough ride... I may end up sending to a dealer with a presence here as at least I know Doug and Steve and their respective crews know what they’re talking about and will get the job done.
 

tjv

Active member
An update:

It wasn't the sliding back or the sensor at all.

In short, after around 8 years of pretty heavy use the rise / fall mechanism on the rear standard had become ever so slightly loose / worn, causing the back to sit differently depending on position and weight distribution.

Linhof Studio were amazing, and have also rest all other zero points and movements to proper parallelism and most other things had slipped a little since new as well.

Happy camper now!
 
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