Rodenstock 55mm and 58 XL 72 XL optimum apertures (HABS work).

[schafphoto]

Hello,

I am building a prototype a 5x7 shifting technical camera to increase my precision on Historic American Buildings Survey ( HABS/HAER/HALS ) projects (and because I need a more durable camera than my 5x7 View). I have a copy of a 72XL in a helical focus mount (the widest lens for 5x7) and I plan to replace my Schneider 65mm 5.6 with a 55mm Rodenstock or a 58mm SXL. Both will only work on the 4x5 reduction back, and will be mounted on a recessed board in a helical mount.

I have read in other posts that the optimum aperture for the 55 Rodenstock is f11 which would follow the old rule of about 3 stops from wide-open is sharpest. The Rodenstock catalog also pegs the Image Circle specs at f11 instead of 22 like most other lenses. (my Nikon f8 90 was tested at f16).

I guess I'm jumping to the conclusion that the 58 XL and 72 XL are best at f22 since that is the aperture where their lens charts seem to test them. I must admit I always attempt to use the 72 XL and the 90 Nikon at f22 when in the field (exteriors and interiors of buildings). But that may be an old Brooks habit rather than a Best Practice"... maybe I should try to achieve f 16 on my Nikon rather than f22. And if I buy the 55 Rodenstock should I feel confident that at f11 I'm getting superior sharpness? I must admit that the extra stop or two would be nice. Maybe I should be trying for f16 on the 72 XL?

In general I am not looking for huge depth of field, there is usually only one plane in focus and outside of extreme shifts, there are no movements in my process. I know this is splitting hairs and my f22 approach is fine, but I'm always looking for process improvements.

But if I can feel comfortable with f16, I'll take the extra bit of shutter speed – especially when I'm in a bucket truck or a windy day. Actual data and general opinions appreciated.

-Schaf

[Bob Salomon]

Just download the info on lenses from Rodenstock by going to our web site: www.hpmarketingcorp.com, click on the Rodenstock link and at the bottom of that page the factory site. All of the specs are there for download including info on the helical focusing mounts for their lenses and the center flters.

[schafphoto]

Thanks Bob, as you can see from my post, I've already been there, I was looking for a little more depth than the marketing brochure's statement... "A large working aperture of 8-11 allows advantageous, shorter exposure times for outdoor motifs".

I just can't imagine that I will get my best results at f8. The point of my post was that I have "very acceptable" results now, and to delve into best practices.

[Mark Sampson]

Try each different aperture and see if there is any apparent sharpness difference. Only you can decide what your optimum f/stop will be, as that's a function of your total practice. I'd bet that the lenses you mention will be up to the task.

[Lachlan 717]

Old theory says that any lens is at its sharpest around 2 stops under maximum aperture.

Thus, when DOF is not critical, I shoot my 72mm XL at f11.

I doubt that I'd notice any difference shooting it at f16 because I shoot reality, not test charts.

[schafphoto]

Thanks, I don't own the 55 or 58 yet to test but you have inspired me to do a test of my 72 XL in a real world situation... will report back.

-Schaf

[Bob Salomon]

Thanks Bob, as you can see from my post, I've already been there, I was looking for a little more depth than the marketing brochure's statement... "A large working aperture of 8-11 allows advantageous, shorter exposure times for outdoor motifs".

I just can't imagine that I will get my best results at f8. The point of my post was that I have "very acceptable" results now, and to delve into best practices.

F11is optimal aperture on the Apo Grandagon series. That is why the specs show the performance there. At f16 you will begin to be in diffraction.

[schafphoto]

Thanks Bob, Well that's a sufficient reason for buying the 55 right there. If the 58mm XL is optimum at 22. I'll take the 2 stops, especially when I'm at 2 seconds and reciprocity is looming.
-Schaf

[Ed Richards]

You are not going to see diffraction in the world on LF film at f22. There is a big gulf between optical bench tests and the field. If I were a betting man, I would bet that you cannot see a difference between 16/22/32 with the 72XL. Try it

[Lachlan 717]

If I was faced with your choice, I wouldn't worry about theoretic maximum resolution figures.

I would choose the lens with the biggest image circle.

Most modern lenses, excluding a lemon, will be plenty sharp enough in the centre and get softer as you move further to the edges. If you are shooting Architecture, chances are you'll be shifting/raising the image. As such, you'll be moving out of the central sharp zone towards the (usually) less-sharp edges.

You'll see more benefit from a bigger image circle than any difference between lenses in f11/16/22 sharpness.

[schafphoto]

And that is why I asked the question... I'm looking at the 55 and 58, and their ICs are:

55mm Rodenstock Grandagon is 163 mm at f11
58XL Super Angulon is 166 at f22 ( and probably closer to 160 at f11)
The difference between a 7 or 9mm front rise.
Both take 67mm filters. The Rodenstock is 80 rams heavier.
So in theory the IC of the 55mm is bigger if I am planning to use it outdoors on a building at f11.
Thanks this is getting very interesting.

-Schaf

[B.S.Kumar]

I have the 45, 55, 65 and 90 Apo-Grandagons, and most often use them at f/16, due to DOF requirements. I have on occasion used them at f/11, and can't say I've found any significant difference in sharpness.

Kumar

[ic-racer]

Bob told us that the lens is sharp at f11. You are probably going to have to stop down more than that to get your subject in focus, and therefore your optimum aperture for each image will be determined by defocus and diffraction, just like any other lens.

Since you are contact printing (right?) the 'math' estimates that you should be able to go down to f45. But of course that depends on you eyesight, viewing distance, potential for examination with a loupe, etc. Only you will know.

[schafphoto]

So True, I will know after I get a copy of the two lenses on my wishlist... In theory HABS does manifest itself in contact prints, but the reason for large format is the high negative resolution of details that would be lost on a smaller format, those details presumably will be seen by researchers examining the negs/scans in detail. Otherwise we could shoot 35mm and get sharp 4x5 prints.

[ic-racer]

So True, I will know after I get a copy of the two lenses on my wishlist... In theory HABS does manifest itself in contact prints, but the reason for large format is the high negative resolution of details that would be lost on a smaller format, those details presumably will be seen by researchers examining the negs/scans in detail. Otherwise we could shoot 35mm and get sharp 4x5 prints.

So the way I would put it all together is that if you are shooting a flat surface of a building, use f11. Otherwise, for 3 d subjects, the usual DOF and focusing guides may not give good info, because of the potential for a magnified view of the circles of confusion and Airy disks. You could re-calculate a DOF guide for an acceptable circle of confusion size 8 times smaller than 'usual viewing' (assuming 8x loupe to examine the negs/prints). When you get the lenses you will probably want to make some negatives at various apertures and see how they look under a loupe.

[schafphoto]

I think I will find a brick wall behind a chain link fence and expose some HP5 at different F's. I've been photographing for 20 years without "Airy discs" and the circles of confusion are usually larger in the 8 inches behind my camera than on my film...

[schafphoto]

I don't suppose anyone has tried photographing with a 55mm, 58mm, 72mm, etc on 8x10 film to really measure the circle. It would be interesting to see how far the illumination circle goes in comparison with the circle of acceptable detail... Those black clipped edges are more noticeable than unsharp, diffracted or out of focus sky corners.
I remember seeing the corners of my 65mm Schneider 5.6 get Wonky and put a wave in a hardwood floor before they fell off to oblivion... however if the bottom of the frame would have been a featureless cement floor, I would never had noticed.

[Photomagica]

Stephen,
I've done some very, very careful tests with a 150mm Nikkor W on 4x5 and also with an 80mm Planar on a Hasselblad 500CM. The largest factor affecting sharpness proved to be the coincidence of the film with the ground glass position and the flatness of the film.

The film position and flatness needs to be held to a very, very small tolerance to get the best out of a modern lens. And yes - this does show up in real world situations.

After I tuned the position of the ground glass in my 4x5 and performed film checks to confirm it coincided with the film position in a holder that was known to be good, I could see a real difference in my results. I then matched all of my film holders using a measuring jig and a light touch dial indicator.

Among the holders there were a surprising number of rejects, with many having errors twice the ANSI tolerance. This tolerance was set decades ago and is is too big by a factor of two, based upon my tests. Some of the best holders turned out to be old Kodak wooden ones. New plastic holders like Fidelity Elite were generally good, but plastic holders made prior to about 1995 were highly variable. A small percentage of plastic holders turned out to be warped - simply not flat.

For 4x5 the ANSI specification is for a film surface depth of 0.197 inches +/-0.007. I checked 50 film holders, with film in them and found the average depth was 0.190. Then I selected holders that were (mostly) within +/- 0.003 inches of this based upon the average depth of 9 locations on the surface of the film.

I also checked how well I could focus the camera, by attaching a dial indicator and then doing a large number of refocusings and averaging the result. The result was a mean error of +/- 0.0013 inches and a maximum error of +/-0.0045 inches. This test taught me I could achieve best results by exercising extreme care in focusing. This test was done with an 8x magnifier.

In building your camera, I urge careful attention to film depth, flatness and focusing to get the best out of the extremely high quality lenses you are considering.
Cheers,
Photomagica

[schafphoto]

Thanks, I'm not going to take my holder flatness for granted any more... I'll test mine they are a mixed bag.