It's true that the collimation of the lenses may vary a bit if the cell is not tightened, but I guess this is irrelevant for that test, when I made those tests I moved with the hand the front cell to see the effect of that clearance, I saw no practical effect.Originally Posted by Leigh
Anyway we can remove that clearance by making/using paper/cardboard/mylar shims.
Yes. I played with loosening the front element of a Fujinon (240A) and took photo's at the centre and halfway across the image circle at every full rotation of the front element (fully seated and four rotations in all). At every full rotation I refocused before taking the shots (object of focus was 25 metres away). In all five sets of images captured with a digital back (6μm pixel size) there was no discernable difference in image quality at 100% view on the computer screen.
That said I didn't check to see if there was any difference when the lens was focused closer or focused at infinity. I also didn't check for field tilt*, where the axis of tilt would be along the horizontal plane. It was a casual test just to satisfy my personal curiosity.
*EDIT 16th Jul.: Field tilt is the wrong definition to use as it correctly refers to the whole lens not the front lens group which I was discussing. My bad. Is decentring more accurate?
Last edited by duff photographer; 15-Jul-2018 at 15:50.
Fujinons usually don't include shims, until I know. My guess is that the Fujinon designs make preformance not that dependant on cells spacing.
I the other hand we have have designs (like some from rodenstock) that require an accurate shimming (done in the the front cell).
Let me speculate a bit... My guess is that in some designs the cells spacing impacts in how the aberrations are corrected, so intentionally the design uses the lens spacing as a degree of freedom in the design to optimize the lens.
Papi, several centuries ago I noticed that Polaroid Copal shutters have somewhat longer tube lengths than jes' plain Copal shutters. Since I wanted to put some 210 mm cells of a plasmat type lens in a Polaroid Copal #1 I asked my friend Eric Beltrando (visit his site dioptrique.info) for his opinion. Eric has written a ray tracing program and used it to provide calculated curves, spot images etc. for lens prescriptions in his database.
He told me to go ahead and use the shutter. His calculations indicated that in general plasmats' image quality isn't very sensitive to small errors in cell spacing and that 0.2 mm is 0.1% of 210 mm, not enough to worry about.
If no Fujinon LF lens has shimmed cells and some Schneider and Rodenstock lenses do, there are two possible explanations. Fujinon had better quality control, or Schneider and Rodenstock were more nearly perfectionists. In all designs cell spacing affects corrections.
OK, but in some designs it perhaps has a way greater impact.
For example a Symmar Convertible has its cells individually corrected, being a single cell usable, with the limitations a simple triplet design has.
But let's imagine that a design undercorrects Chromatic Aberration in the front cell while overcorrecting it in the rear cell. Then if we vary the cells spacing we can adjust the correction to the optimal point, as the amount of deviation added from front cell would depend on the lens spacing.
Then we can imagine that spherical aberration correction has a well lower dependence on the lens spacing, so if from the production crop we pair cells that compensate well the spherical aberration in particular then we would be able to minimize the chromatic aberration by shimming, obtaining a consistent quality production.
Just thinking in an hypothetical way to use shimming that's not related to overcoming manufacturing inconsistency, in fact the great amount of shimming that some Pro designs bear are not easy to explain from production inconsistency (IMHO).
A possibility is that (in some designs) cells spacing is an open paramenter for the manufacturing, that would allow a greater number of front/rear cells excellent combinations found.
Just speculating...
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Oh, yes... I've been exploring dioptrique.info since you pointed it to me time ago. Nice info !
Papi, if we had eggs we could have ham and eggs if we had ham.
I figured I would resurrect this thread from the dead to post some quick follow-up, four years and many sheets of film down the line. I will be mercifully brief.
1. 8x10 is a wonderful, demanding format. I find it best for things at moderate distance...it seems to be most distinctive when photographing objects and people within 10 meters or so, to get the lovely impression of the out of focus fall off. With long distance compositions, I see less of a difference to 4x5 for moderate sized prints...superior tonality and sharpness for sure, but those advantages are harder to spot until the prints are huge.
2. Everyone who said to get a wooden tripod was correct. I thought my BH55 would be enough, and it certainly is enough to "hold" the camera, but holding and stabilizing are two different things. This is partly an issue of the small contact area in an arca plate, versus a large, flat platform head. Especially in windy Iceland, a Ries with a platform head has been dramatically more stable and well worth the bulk and hassle if working for a car. I just wish someone would design a wooden tripod as solid as the Ries but without the pointy, sharp aluminum knobs sticking out everywhere. I would basically want a wooden RRS/Gitzo style locking, but clearly that would require hollow wooden tubes, which is obviously not going to work...
3. As expected, there are some real differences in lens characteristics and quality. My first lens was a 305mm G Claron, and while it has worked fine, it did not really bring what I was looking for. In the end with a lot of patience I found very good deals on three dedicated 8x10 lenses. A 240mm Sinaron SE, a 300mm Fujinon CM/W and a 450mm 12.5 Fujinon C. All are in excellent condition and very sharp. I find myself using the 240mm and 450mm the most. This is not too surprising, as I found my 110mm and 210mm lenses most used on 4x5. Of all of them, the 240mm stands out for sharpness and clarity. It is easiest to focus due to the high sharpness wide open and the bright 5.6 aperture. I would highly recommend this lens. My next favorite is the 450mm 12.5. Despite the slow aperture, it is still fairly easy to focus, though it does not snap in quite so readily as the other lenses. It is very sharp even at f16 or 22, and has a very pleasing character. The show stopper of this lens is of course the tiny size and weight given its huge coverage and long focal length. Of the three, I have had the lowest success rate with the 300mm Fuji, and I am not totally sure why. I have made some photos with it where it has been very very sharp and lovely in character, in particular one portrait. But for landscape work it seems not to be quite as strong as the other two. It may be a self-fulfilling prophecy at this point, as I tend to stick to the other two lenses for longer distances. But in the images that I have shot with this lens in the closer range (up to 10m), it has been sharp and lovely.
Here are some quick pictures. The B&W portrait of the man is with the 300mm Fuji. The eyelashes are tack sharp, and this is just a flatbed scan on an Epson. I think this is an excellent performance.
The color building is shot with the 450mm, with front rise. It too is sharp enough to see people's vases and trinkets in the windows in the buildings. I would post another from the 240mm, but it seems I can only post four images.
In any case, I hope this experience might help someone if they are asking a similar question to me.
PS, I see that the attached images have undergone a degrading process when uploaded. Please just take my word for it. They are sharp. BTW, I am typically using f16 or f22.
Interesting about your experiences with the wooden tripod.
Through what I've read in this thread, I'm wondering about what 8x10 camera that you're using?
Thanks Neil. I am using a Chamonix 810V. Quite light, but Iceland is the windiest populated country in the world, so it could just be specific to the environment...but what I found was a combination of both the wood and the platform. The platform may be more important...having a very large mating surface under the camera does a much better job of eliminating flex. The wood is also much more "dead"...it seems to absorb the vibrations more quickly than the carbon fiber. I have a full size studio stand at my lab, and the Ries is even a lot more stable than that, which is aluminum and probably over 100lbs. I don't always manage to carry it...the bulk is worse than the weight, but when I do have it, it is a great asset. The BH55 and TVC33 are great, but there is a lot more flexion and vibrations seem to linger longer and be transmitted better. At first I though some of my lenses were soft, but it was really the tripod...
Previously posted on the "goodness" of wood tripods. While this "white paper" is specific to surveyor tripods, much identical applies to Foto tripods.
https://www.largeformatphotography.i...od-white-paper
There are very real reasons why high quality wood remains a top choice tripod material for surveyor, astronomy telescopes and demanding Foto needs.
Too many folks new to view camera today is overly focused on the lowest weight view camera while neglecting the other components of the view camera image creation system like how Important The Tripod and Tripod Head IS.
IMO, focus on lowest weight/bulk and related is often the root of SO many view camera issues. Reality and facts are, this view camera image creation stuff is all a set of trade offs, there is no miracle widget in the future that will be a projection of the lowest weight/bulk fantasy, just harsh reality and limits of what Nature/Physics will allow.
Too often the lens is blamed for image issues the lens is not responsible for, like flimsy tripods, flimsy camera, wavy film in the film holder, limitations/skills/ability of the image creator and more.. when the lens was doing it's job proper.
Bernice
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