Re: LF vs MF lens quality
Dan, this isn't just an impression, it is in many cases a fact.
Given a "good" lens (ie: one that was maufactured correctly) the limiting factor in any format is film.
For TMax100 in D76, this means around 120 to 140l/mm. Similarly with Velvia and other fine grained color film as well as Delta 100 and in some cases other slow traditional grained films.
On a practical level, I am currently showing images from southern India temples. During the reception I challenged viewers to correctly guess which lens/camera/format various images were made with. All are very sharp. All are very contrasty. And the viewers were mixed newbies and working pro photographers. The differences are subtle enough that even with people using their reading glasses (OK, so we're an old crowd) no one correctly guessed even a single image. I used Rolleiflex TLR, Mamiya 7, and 4x5 - mixed TMax100/400 and enlarged to 11x14.
Quote:
Originally Posted by Dan Fromm
... With good lenses, I have the impression (= won't fight to the death to defend the idea) that film, not the lens, is limiting.
Re: LF vs MF lens quality
Deeply flawed? OK. Well...
In my case I took a Linhof III and calibrated the ground glass to +/1 0.04mm of specification. Then I set the camera at a distand 20:1 the focal length of the lens under test. Then I used TMax100 souped in D76 in all cases. Then I looked at the results under 160x in all cases. Most of the time I used my eyes to focus. Sometimes a friend came over and he did the focusing. These were the test conditions. Seems pretty consistant to me.
I fail to see how testing and retesting a single optic would be of benefit. I did exactly that at first and realized results were absolutely consistant in 4x5 optics. So why retest and retest again? What's to be gained? Does a camera system resolution change over varying subject/camera distances? ** There is a single case where retesting made a difference and that we in a 120 format system that I had continued access to.
** The answer to this is yes. In the case of 4x5, 20:1 working distance seemed about right for various lens designs. And, anyone working at infinity will seldom ever realize the full resolution potential of any lens due to image distortions introduced by roiling air.
Quote:
Originally Posted by JW Dewdney
Did you have some sort of comment on these Eric? I've actually spent quite a bit of time looking at these results. While Chris has gone to a hell of a lot of effort to get these numbers, my feeling is that it was a deeply flawed study. There's no control in place to objectify focus accuracy or many other factors. There would appear to be only a single trial for each lens (when there ought to be, say, 10). Only a single sample of each lens was used. The one common trend that I DO see in the numbers - is a linear drop in resolution with Focal Distance (notice I did NOT say focal LENGTH). I think that's something interesting to think about. My guess is that the degradation to resolution number with focal distance would be a diffraction byproduct (the further away you measure the amount of diffraction - the greater the diffraction becomes). So - "what is my point?" you ask...? I'm trying to suggest that the numbers you see have nothing so much to do with 'lens quality' so much as being built into the format itself - esp. where focal distance varies so greatly. Just a thought.
Re: LF vs MF lens quality
Wow. Really?
I took a stack of v.sharp 35mm down to the art director and she brought out her 20x loupe. Then, for grins, I threw down a few 4x5 chromes taken during the same photo session. She instantly turned to me and said "Now we're talk'n!... these I can work with... [peering through her loupe] and LOOK at that resolution and contrast!... it's as good as 35mm... and the size of these chrome... [drool]... please don't ever bring me 35mm again...
End of discussion. :)
Quote:
Originally Posted by Andre_941
Anyone who thinks Large format lenses (even the vaunted Rodenstock Apo Sironar-S 150) are as sharp as a good prime 35mm lenses has never taken a decent loupe to images shot at f8 with the Nikkor AFS-I 300 f2.8 lens.
I have, and the discussion ends there.
Re: LF vs MF lens quality
Quote:
Originally Posted by Christopher Perez
Given a "good" lens (ie: one that was maufactured correctly) the limiting factor in any format is film.
What do you mean by this?
I really don't get it. MTF performance of films like TMX trounces that of any photographic lens.
Even ignoring this, how can you really speak of limiting factors in a signal chain where every stage is capable of reducing the quality of the final image?
Re: LF vs MF lens quality
Chris, I think we're pretty much in agreement. Like you, I standardize on an emulsion and a shooting distance. Unlike you, to the extent possible I use the same shutter for all lenses. This eliminates slight (usually, sometimes they're large) variations in exposure that can bias judgements of color rendition. Basically, as long as veiling flare isn't a problem, with one exception undergoing retest (see below) I find no differences in color rendition among my lenses.
We don't quite agree on one point. Film isn't quite limiting with all of my lenses. The 200/4 MicroNikkor AIS I mentioned is my weakest Nikkor for 35 mm. I'm on my second one; it performs consistently with the first. The first shot and its replacement shoots consistently with MP's test of a third one. Not as sharp as, say, the 55 or 105 manual focus MicroNikkors and not as constrasty either. Just usable enough that I can't convince myself to sell it and get a 180/2.8.
I'm glad that you've tried to get people to match lens/format to image. Bob Monaghan did much the same thing with much the same results. And I've done the exercise, with same shutter and emulsion within group. Sometimes its possible to identify some of the images as a little sharper than the others, but so far no one has been able to match image to lens. There's one semi-exception that I think was due to shooting out-of-doors; all four shots (f/9 through f/22) from one of my 150 Apo Ronars came out quite blue. I believe that the sun was behind a cloud during that sequence, and I got one other blue shot that day between two normally colored ones with the same lens etc. Roses are red, shadows are blue. Because of their blue cast, the one AR's shots stand out from the others. Otherwise, when the images are scrambled and the slide numbers hidden sorting is impossible.
Cheers,
Dan
Re: LF vs MF lens quality
Quote:
Originally Posted by Christopher Perez
I fail to see how testing and retesting a single optic would be of benefit. I did exactly that at first and realized results were absolutely consistant in 4x5 optics. So why retest and retest again? What's to be gained? Does a camera system resolution change over varying subject/camera distances? ** There is a single case where retesting made a difference and that we in a 120 format system that I had continued access to.
** The answer to this is yes. In the case of 4x5, 20:1 working distance seemed about right for various lens designs. And, anyone working at infinity will seldom ever realize the full resolution potential of any lens due to image distortions introduced by roiling air.
By and large I would agree with you regarding most lenses, but I have encountered enough exception cases that I still prefer performing multiple tests myself.
I agree that differences in infinity performance between modern lenses are relatively rare, due to the factors you mention. However, some special design types (convertibles, for instance) may have additional design constraints and may be optimized for a more limited range of focus distances, and some degradation in infinity performance may be quite noticeable. And even with conventional lens designs, exceptions occur. My 600mm APO Tele Xenar is noticeably sharper at infinity versus my Fuji 600C; perhaps a single test at 20:1 might have revealed this, but how can one be sure? Since these long lenses are infinity workhorses, I preferred to make an explicit test at the specific application focus distance.
Regarding close-up performance, my concern is that 20:1 may not always be close enough to capture meaningful performance differences, particularly for larger format shooters who use longer focal lengths. When shooting 8x10, I need sharp performance at distances as close as 15 feet (or even closer), which for a normal 300mm lens equates to roughly 15:1 and for a 480mm lens roughly 10:1. My Fuji 450C performs well at infinity, but is clearly outclassed by my 480mm APO Symmar L at 15 feet. If I had shot at 30 feet (20:1), I suspect that the difference between the lenses might not have been noticeable.
I realize your tests were done with 4x5 in mind, for which 20:1 equates to much closer distances for most common 4x5 focal lengths.
Re: LF vs MF lens quality
Eric, you're right, the only way to find out if a lens will do what's needed is to ask it. I try lenses out in the way I intend to use them. Macro lenses vs. macro lenses and at a variety of magnifications; its amazing how finely tuned to a narrow range of magnifications ones intended for use above 1:1 can be. "Close-up" from 1:8 to 1:1 as practical; this includes process lenses, as practical. I mean, I can't focus my 480 closer than 1:10. Normal and shorter lenses at ~ 100 f. Lenses 2x normal and up at ~ 300 m. I did the MicroNikkor vs. GRII at 1:2 and ~ 40'. And so on.
I keep finding that among my ok lenses the differences are small, as in one could be happy with any of 'em. Its the lousy ones that stand out sharply.
One of this week's exercises was shooting a tessar with mounting threads on each end mounted each way at ~ 300 m. Didn't look too bad wide open on the GG either way, another indication that sharpness is very hard to judge on the GG unless using a target with a wide range of scales. Doublet to the front should be much worse on film, but its an empirical question. I asked the same question of a rather odd heliar type.
One clarification. Unlike those of you with big cameras, all I care about is central image quality. So I often do my trials with the lenses hung in front of a Nikon. Doesn't get all of the information that would be nice to have, gets enough for my purposes.
Re: LF vs MF lens quality
Quote:
Originally Posted by Christopher Perez
Deeply flawed? OK. Well...
In my case I took a Linhof III and calibrated the ground glass to +/1 0.04mm of specification. Then I set the camera at a distand 20:1 the focal length of the lens under test. Then I used TMax100 souped in D76 in all cases. Then I looked at the results under 160x in all cases. Most of the time I used my eyes to focus. Sometimes a friend came over and he did the focusing. These were the test conditions. Seems pretty consistant to me.
I fail to see how testing and retesting a single optic would be of benefit. I did exactly that at first and realized results were absolutely consistant in 4x5 optics. So why retest and retest again? What's to be gained? Does a camera system resolution change over varying subject/camera distances? ** There is a single case where retesting made a difference and that we in a 120 format system that I had continued access to.
** The answer to this is yes. In the case of 4x5, 20:1 working distance seemed about right for various lens designs. And, anyone working at infinity will seldom ever realize the full resolution potential of any lens due to image distortions introduced by roiling air.
Chris - I just wanted to qualify my comments in case you didn't get it the first time 'round. I probably wasn't concise enough. First - let me say - that I think it takes phenomenal dedication and deep care to pull off a study like that. I am disparaging your work in no way. HOWEVER - if this were an actual academic scientific study - you would take several data points for each sample - i.e. evaluate LPM for a 300mm Nikkor-M, say, at center of field and f/8 3-10 separate times.
The reason you would do this is to eliminate 'environmental' factors, such as focussing accuracy, film placement, etc. You wouldn't be able to simply do this in the same setup. It would need to be a separate trial - with teardown of your setup in the meantime. FURTHERMORE, if you're wanting to make an evaluation of a given MODEL of lens - it only stands to reason that you would need to go through the entire procedure for each of 3+ samples of a given lens model. It's completely impossible to establish a standard deviation unless this was done. And without establishing your 'lambda' (std. dev.) most scientists would throw out the results as meaningless.
I DO understand that it would take an INSANE amount of work to do this. I'm just sayin'... anyway - given the already fairly large dataset you HAVE established, we can derive certain things from it. If you were to plot resolution against focal distance - you would see, and COULD establish a std. deviation from the different lens models in the same or similar focal distances. And this is PRECISELY what I have been responding to - a linear drop in resolution with focal distance. I would predict that if you look at some of the medium format results - you'll notice a similar drop in resolution with non-retrofocus design lenses (I think a sonnar 250 is this type- ?).
And this is the ENTIRE crux of what I've been trying to put across to everyone. Simply - that an 80mm Planar in a copal shutter mounted for view camera use will not be sharper nor less sharp than it's equivalent mounted on a Hasselblad or Rolleiflex - the contention also holds for 35mm equivalents - though it's harder to find a lens that meets the non-retrofocus requirement. This is the only way conceivable that you can fairly compare designs in order to negate the effect of focal distance - which is ALWAYS lower for a retrofocus design by definition (except, of course, wide-angles).
Re: LF vs MF lens quality
Quote:
Originally Posted by Christopher Perez
and the size of these chrome... [drool]... please don't ever bring me 35mm again...[/I]
End of discussion. :)
Of course, all women know one thing: SIZE MATTERS.:p
Re: LF vs MF lens quality
I have recently scanned a bunch of 35mm, 6x6, 6x12 and 6x17 shots, taken of similar subjects at more or less the same time. The 35mm were taken with a Canon EOS 3 with Canon L lenses, the 6x6 with Hasselblad and Zeiss, and the 6x12 with a Horseman 45 with Nikon, Schneider and Fujinon. I scanned them all on a Nikon Coolscan 9000 at 4000 dpi. All were on Velvia 50 film. Looking at the resulting scans at 1:1 pixel ratio on Photoshop should therefore be a reasonable comparison of the lens quality, it seems to me. On that basis, the Zeiss/Hasselblad lenses look sharpest to me, followed by LF and Canon L.
Having said all that, there is precious little difference. I do not have a scanner capable of 4x5 yet but I expect they will make the most impressive enlargements.
