Tilt and your tech cam - how often with short lenses?

[cly]

How often do you use tilt with short lenses? Or: Would you miss something if you could only tilt with lenses longer than 80mm? (I'm about to enter Dante's world, main subject is interior design in museums and architecture. Still trying to do my homework ...)

Jack's review of the Cambo with the 40mm Rodenstock (http://forum.getdpi.com/forum/showthread.php?t=13238) shows how useful tilt/swing can be. I am wondering wether the lack of tilt with WA lenses in the Alpa family might turn out a problem.

Thanks for you comments!

Chris

 

[Terry]

I am new and learning to using tilt. That being said, I am definitely using tilt with my 35mm lens on a regular basis (I'm using the Arca Rm3D). I was looking at Alpa gear last week and the fact that tilt only starts at 80mm with the short barrel lenses is a bummer. I'm not expert enough at using tilt or using Alpa gear to give advice but what I can say is that it is very simple on the Arca and you need no additional gear (adapters).

 

[Bob]

My own experience with tilt seems to be primarily associated with short lenses both for landscape and architecture and with longer lenses for product photography.
I would find an 80mm restriction far too long to be useful for most of what I shoot with my P65+.
-bob

 

[GrahamWelland]

As an Alpa user I have to say that the lack of tilt capabilities with wide angle glass is inconvenient for landscape work. If I had it, I'd definitely use it. Instead when I need more DoF I have to resort to stopping down further than I'd like than f/8-f/11 and/or focus stacking & using Helicon Focus - both of which are a pain & extra steps for an image. (Although the same applies to shooting with DSLR too)

 

[jlm]

you might want to read this:

http://forum.getdpi.com/forum/showthread.php?t=13238&highlight=cambo+wrs

 

[rhsu]

How often do you use tilt with short lenses? Or: Would you miss something if you could only tilt with lenses longer than 80mm? (I'm about to enter Dante's world, main subject is interior design in museums and architecture. Still trying to do my homework ...)

Jack's review of the Cambo with the 40mm Rodenstock (http://forum.getdpi.com/forum/showthread.php?t=13238) shows how useful tilt/swing can be. I am wondering wether the lack of tilt with WA lenses in the Alpa family might turn out a problem.

Thanks for you comments!

Chris

Chris,

Bob's rule of thumb with WA and longer lenses usage is spot on.

I have both my HR28/35 lenses with no T/S mount. But my HR40 is T/S mounted.

Prior to HR40, I would us my HR28 permanently on the WRS and a lot of my shots were at infinity @ f8. Yes, I wish I had a 1* tilt to get a bit more DOF.

I now use my HR40 more because of the movements. I look forward to mount my HR28 on T/S as well - but the amount of T/S for the HR28 would be very minimal to justify the cost at this stage - that's based on the minimal amount of movement with my HR40 ie rarely do I go beyond 1-2* @ f8 infinity. Although the IC of the HR40 is 90mm and HR28 is only 70mm, the sensor that I am using would allow me at least 3* more with the HR28. I just have not met a situation that I could say: "gosh, I wish I could get 3* more of my DOF" - that's because I avoided that scenario.

I love to be able to have my HR90 T/S mounted for close up but NOT able to do so at the moment by Cambo people. Only the Digitar 90mm is capable of doing so at the moment. Here lies the adv of Alpa HR90 short barrel mount w/ T/S adapter.

However, do try out Sinar arTec as it allow all 4 movements on the camera and NOT on the lens mount (ie Cambo) - and where you are, you have better access to Sinar. You can then mount most std Sinar mount lenses from HR23 (landscapes) to HR90 and greater (products) onto the arTec and have movements . However, with the arTec, unfortunately, you cannot do both T/S together at the same time like that of Cambo T/S lens mount.

Hope that helps....:thumbup:

 

[jlm]

going by the book, if your lens is 5' above the ground and you are focused at infinity:

43mm lens would need 1.5 degree tilt (the same net fl as the 28 in the hasselblad HTS)
70mm lens: 2.5 degrees

this would produce a plane of focus of the level ground

 

[Pedro Mendes]

With the Artec you can combine tilt and swing,by rotating the lens standard.But it's less convenient than with a tec camera with separate gears for tilt and swing like the Monolith ,because the lens standard of the Artec is not geared and has marks each 10 degrees.
And yes, one degree forward tilt helps bringing the foreground in sharp focus(I use the 40mm Rodenstock).
Pedro.

 

[rhsu]

going by the book, if your lens is 5' above the ground and you are focused at infinity:

43mm lens would need 1.5 degree tilt (the same net fl as the 28 in the hasselblad HTS)
70mm lens: 2.5 degrees

this would produce a plane of focus of the level ground

The Scheimpflug Rule
The gloriously named Scheimpflug Rule says that if the subject plane, the plane of the lens panel and the image plane all meet at a common line, everything in the subject plane will be in focus in the image plane.
:thumbs:

 

[Anders_HK]

Chris,

I am carefully considering getting a tech camera, as such perhaps my thoughts can be of some value.

It is my belief that it is important to focus on the image and what we wish as far as rendering. When looking at the two train car photos in http://forum.getdpi.com/forum/showthread.php?t=13238 I actually prefer the first where the near of train car is sharp and far is not, because it add a sense of depth. Likewise I find similar interesting in landscape images because it add depth. However, I am also someone who prefer to have light fall off in images... because it likewise creates focus. When I say this, do consider that the sensor/film size of a digital back is significant smaller than 4x5, for which tilts are very mandatory for landscapes.

My prime interest is in Alpa since they arguably offer tighter tolerances than any other system made today, including possibility to shimming back, strict fabrication tolerances, roller bearings etc, and the fact that tilts are not built into the camera itself. With cameras having tilts built in it appears to me as one factor that need to be zeroed to perfection for each shot and which is difficult if not impossible to make to same tolerances one can shim an Alpa. Why? Lets remember Alpa can be shimmed to 0.01mm tolerance. That is extremely small. All is a trade off though, thus depends on our preferences and intended use. Thus, what do you prefer, tilts or the preciseness of an Alpa?

A thought of something to complement an Alpa system with is for me a Shen-Hao 6x9 non folding camera to add movements for select situations. If that one would be fitted with a rear mount to enable mounting Alpa groundglass and back mount to tight tolerance this would add what is most critical in chain when needing accurate focus for tilts for select situations (the tolerance in plane between groundlass and sensor of digital back). Rodenstock makes a 6x loupe that covers a reasonably large viewing area and which can be used to focus.

I hope above help or at least share some different considerations. :salute:

Regards
Anders

 

[jlm]

I would postulate that the precision and shimming of the alpa is only useful to ensure that if your lens is on the infinity stop, on the stop, not just the pointer on the mark, you are in focus.

at any other focus distance, the imprecision of the lens distance markings, coupled with however you measure distance to subject, completely override any high tolerance shimming. and if you are using the gg, shimming is not a factor.

the shimming i am referring to is only for distance to film plane, not parallelism

 

[Terry]

Chris,

My prime interest is in Alpa since they arguably offer tighter tolerances than any other system made today, including possibility to shimming back, strict fabrication tolerances, roller bearings etc, and the fact that tilts are not built into the camera itself. With cameras having tilts built in it appears to me as one factor that need to be zeroed to perfection for each shot and which is difficult if not impossible to make to same tolerances one can shim an Alpa. Why? Lets remember Alpa can be shimmed to 0.01mm tolerance. That is extremely small. All is a trade off though, thus depends on our preferences and intended use. Thus, what do you prefer, tilts or the preciseness of an Alpa?



Regards
Anders

Why do you say that only Alpa has the possibility of shimming backs? Technically couldn't you shim the back with any system?

On the Arca system you can calibrate focus.


.

 

[jlm]

i should also add that the alpa concept shimming of the back does not carry over for multiple lenses. Wouldn't it have made more sense to shim each lens?

 

[GrahamWelland]

i should also add that the alpa concept shimming of the back does not carry over for multiple lenses. Wouldn't it have made more sense to shim each lens?

That's what you pay the extra Alpa tax on the lenses for. They are supposed to be accurately calibrated to the mount and the precision of the lens mount/body/spacer/back plate is supposed to be set and consistent. The only part not set up by Alpa is the digital back so hence the shunning per application. (That said, I'm sure as an engineer you could argue that there's tolerance at every step in the chain ... Etc etc oke

 

[David Klepacki]

Hmm ... It seems people have already "forgotten" the lessons learned from Joe Holmes:

http://www.josephholmes.com/news-medformatprecision.html

According to Joe, the lenses for ALPA cameras are just as prone to inaccuracy as for any other camera, as he found large variation in image quality from both their Rodenstock and Schneider digital wides.

 

[jlm]

that was a lot to wade through!

written in 2009...I'm hoping the Schneider and Rodenstock lens quality is improved, as he implies, but it looks like you have to personally calibrate each lens to your body/back to guarantee infinity focus can be achieved.

the lesson to take home is that a 16 micron shift (about 1/6 the thickness of a sheet of paper) in lens to sensor distance constitutes a change in subject distance from infinity to 200' (for a 35mm lens at 5.6, if i recalled it correctly). makes the superfine helical focus ring on the arca seems sensible

 

[GrahamWelland]

Hmm ... It seems people have already "forgotten" the lessons learned from Joe Holmes:

http://www.josephholmes.com/news-medformatprecision.html

According to Joe, the lenses for ALPA cameras are just as prone to inaccuracy as for any other camera, as he found large variation in image quality from both their Rodenstock and Schneider digital wides.

If that's directed at my post then I'd also say that it seems that people have already "forgotten" to read the whole post too.

Manufacturing tolerances are a fact of life. Sure, the arca approach of dialing in a calibration offset per lens (once you've determined what it is of course) whenever you use that lens, and using a chart/guide to map their focus dial to real distances, should provide a correct focus for that lens/back combo. However, when the sun is rising rapidly, you're freezing your butt off, you're trying to make sure that the scene is composed just as you want it, its dark as well just for good measure, now tell me that you'll dial in the correct offset, look up the focal point mapping and shoot the shot every time? :watch: I'm just saying ...

Btw, I have a great deal of respect for Joseph Holmes and his tests, however, I recall that both Rodenstock & SK recommend pretty much any of the lenses he tested to be shot optimally between f/8 & f/11 with MFDBs. Pretty much the only glass I personally expect to perform optimally at their maximum aperture or +1 are Leica RF lenses. (and I'm not wishing to start a Leica lens war either btw).

 

[Terry]

Graham - I think that is a little overly dramatic about how you use the Arca. Most people only have a couple of lenses and any adjustment factor is really quite small and simple to remember. In addition with the wider lenses for landscape you are working with a pretty short range of the focus helical.

 

[David Klepacki]

Graham, I was just pointing out Joe's analysis and that Alpa has no tighter tolerances or precision than any other quality camera maker (e.g., Sinar, Arca, Linhof). In fact, I was careful not to advocate any one camera vendor over another in my post, so am not sure why you want to compare against Arca now. However, since you bring it up, I do agree with Terry here, and also that the Arca can still be shot in the same manner as any Alpa, and so it is not limited to the procedure that you describe.

Also, Rodenstock does recommend F5.6 as an optimum aperture for their 28mm and 35mm lenses that Joe discusses.

David

 

[Anders_HK]

Following is my go relating to a number of the above recent posts. Comments are much appreciated and will assist in my own evaluation of deciding to go ahead with tech camera.

Graham, I was just pointing out Joe's analysis and that Alpa has no tighter tolerances or precision than any other quality camera maker (e.g., Sinar, Arca, Linhof).

I missed that part. Appreciate if you would please paste a quote, thanks.

That's what you pay the extra Alpa tax on the lenses for. They are supposed to be accurately calibrated to the mount and the precision of the lens mount/body/spacer/back plate is supposed to be set and consistent. The only part not set up by Alpa is the digital back so hence the shunning per application. (That said, I'm sure as an engineer you could argue that there's tolerance at every step in the chain ... Etc etc oke

I am an engineer, dont hit me! :OT:. What Joseph Holmes mentioned of the various parts, camera body, lens etc contributing to the whole is correct for basically anything that is fabricated. Not only that, each camera body, lens assembly etc is assembled of various components that each are made to specified fabrication tolerances, in order for the summation of all tolerances to result in a total of the component (e.g. camera body) being itself within a specified tolerance. Certain expensive high tech machinery is capable to fabricate individual parts to within 0.01mm tolerance. My guess is that is what is used to fabricate an Alpa system, and perhaps also Arca and Cambo components? However, the individual tolerances indeed add up to a total whole that is likely adjusted in fabrication in various ways at different stages. In this regards my guess is that Alpa makes their system as whole to tighter quality control, thus tighter tolerances.

For a tech camera, it is also absolute important that the lenses be mounted and adjusted for the lens plane to be perfect parallel to the sensor plane (or back mount), and within tolerance to the acceptable tolerance to achieve focus. However, as Joseph Holmes mentioned, a loaner back was off by 175 micron, which is 0.175mm and which is huge in comparison (you will see that from what I type below). I would guess that back was a rare one…

Back to Alpa...

I would postulate that the precision and shimming of the alpa is only useful to ensure that if your lens is on the infinity stop, on the stop, not just the pointer on the mark, you are in focus.

at any other focus distance, the imprecision of the lens distance markings, coupled with however you measure distance to subject, completely override any high tolerance shimming. and if you are using the gg, shimming is not a factor.

Unlikely. The very nature of a lens being calibrated is that the infinity marking is calibrated since that is the reference mark for calibration. Thus, then consider that the turn of helical focus is large compared to the focus travel of the helical. This is why I believe what you state is not correct since you would be in control of focus point thanks to the calibrated tolerances of the system.

As example, per what I was told by Schneider the critical tolerance of camera systems with adjusted flange focal distance at infinity is 0.02mm. Thus the infinity index of the helical mount has to be adjusted individually to the effective focus length of each lens to get a sharp image on infinity, or if this is failed by 0.02mm one cannot get a sharp image (per Schneider). Thus, obvious the loaner back that Joseph Holmes mentioned that was off by 0.175mm had a big problem. I am not sure if backs are always made to within 0.02mm (perhaps they are not), but obvious the shimming of Alpas (or “fudge” factors applied to tables for Arcas) do bring to within that tolerance, provided of course... that the sensor is perfect parallel to that camera system (and if not Alpa is the only one that offer a system of corner shims to compensate…).

As we see, we are fighting for very precise tolerances…

Now, 0.02mm is indeed very, very small and the turn on helical focus will need to be larger, or simply it will be very difficult to adjust focus for an image at any other setting than the infinity lock (if… at all that has been perfect calibrated to within 0.02mm tolerance).

For the Schneider 24mm lens (which may be an exception with unusual small focus travel), the total focus travel from 1.5m to infinity is only 0.3mm. That is already very small. Thus it is perhaps not a wonder that Joseph Holmes found problem with this lens when focused at wide open. While the lens is recommended for use within f/5.6~11, what that means is that the lens is capable of being sharp within that aperture range. However that does not necessarily mean that the helical focus is capable to at all times reliable focus at those apertures, because a helical focus too has tolerances. Perhaps with use of a groundglass on an Alpa the chance of precise focus would improve, if assuming that the tolerances between groundglass and sensor are smaller than between sensor and helical and measurement to focus point??? Notably for the 24mm Alpa seem to offer their own helical focus... perhaps it is designed to be more precise??????

Alpa enable the user to shim a back using shim plates as small as 0.01mm in order to ensure that it be shimmed to their system which is already within the critical 0.02mm tolerance. This is per my understanding (if I am correct) what really sets Alpa apart, including of course that all components also ensure of the total system (less back adapter plate) of being perfect parallel to lens plane. Thus all parts in Alpa system comes per my understanding already calibrated to very exact tolerances from the factory and which ensures to within 0.02mm critical tolerance. However please feel free to fill me in or correct me if I am wrong. I am keen to know and understand more.

Thus with any body or lens of the Alpa system it should be possible to focus to high (acceptable) accuracy within the critical 0.02mm tolerance using any shimmed back. Other fabricators such as Arca and Cambo as example do not provide their systems with such readily precise tolerances from the factory but while perhaps fabricate components to 0.01mm tolerance do not carry tolerances through to ensure the system being as exact as Alpa, or is my understanding incorrect??? Thus the lenses of those systems may need to be calibrated individually, or "fudge" factors may need to be applied such as for Arca, and which may or may not be different for different lenses (note). Correct? Indeed please feel free to shoot or correct me if I am wrong in what I write. This said, it is possible that the helical focus of Arca enables more exact adjustment of a focal point at wide open and with tape measure or laser, if a correctly calibrated “fudge” factor is applied to the scales, if that helical focus is fabricated to exact precise tolerances to match its turns…. For some applications perhaps that is desirable system and preferred means to work, albeit seem tad tedious. For landscapes I am uncertain if it is necessary with such system, Alpa's appear more simple to use to myself, yet we speak of perhaps preferences...

Back to tilts; with the critical 0.02mm tolerance it is my understanding that tilts cause complication, or??? 0.02mm is a very exact tolerance within which for each shot not requiring tilt that the lens will need to be zeroed to such tolerance. Perhaps the IQ backs with live view and focus confirmation a’la C1 “green mask” will assist in making that adjustment to point that it will not be much of an issue anymore, who knows??? However, there must also be risk that the tilt/zero adjustments get thrown out of tolerance between each shoot, or? Now, with this why would I speak of a Shen-Hao as a complement to an Alpa? Because the Alpa groundglass adhere to the within critical tolerance of the Alpa system and thus focus using the groundglass should result in acceptably sharp images using a shimmed back, if a custom mount with perfect flatness to fit the Alpa groundglass/back adapter is custom made for the Shen-Hao. The adjustments would be tedious and used for certain circumstances, but utilizing an aperture to yield a large DOF than wide open there will be some margin, perhaps even with a larger than required DOF the adjustment of tilt and shift will not be much issue???

Comments are very welcome and much appreciated. :thumbs:

Regards
Anders