LF resolution compared to smaller formats?greenspun.com : LUSENET : Large format photography : One Thread
I'm new to LF and just got a Wisner 4x5 PE. After getting comfortable with basic movements, etc I took a couple of test shots last week. My exposure was just what I wanted, and at first glance focus seemed perfect too. Under my 8x loupe, however, the image resolution was a lot softer than I expected. With Toyo 3.6x loupe, the difference is not as noticeable.
My question: should I expect a lot softer LF images than I'm used to getting in 35mm and 6x7? I know that I can't expect it to be identical, but this is quite a lot softer. I compared to chromes from my Mamiya 7, and while its lenses *are* extremely good, there is simply no comparison in detail. I've never examined LF chromes "up close" before, so I have no other basis for comparison.
Equipment used: Wisner 4x5 PE with Fuji 300mm "C" lens, on Fuji Astia Quickload film in a new Quickload holder. These are shots in a local state park, of trees and lakeside, with much detail *available* in small twigs, reeds, etc. First shot 1 sec @ f/32.5; second shot 1/2 sec @ f/45 (sun came out!). I focused VERY carefully using the Toyo loupe and darkcloth, and checked focus again after removing the QL holder each time. I purposely took shots requiring only a small amount of tilt, in the interest of keeping it simple the first time.
Ron Wisner is strongly biased in favor of "loose" sheet film, and says that QL is soft in comparison. So many of this forum's readers use QL, however, that I can't imagine the difference is that great.
Am I expecting too much, or do I have a technical problem? My first thought is that there may be a film plane problem i.e. correlation of the GG with QL holder...I'd be most appreciative of any advice offered...thanks!!
-- Danny Burk (email@example.com), January 16, 2000
It is likely that smaller format lenses can have better resolution given that they have lesser constraints in terms of covering power etc. However, the numbers are not an order of magnitude different (whereas enlargement ratios can be) and I think the best lenses deliver comparable resolution figures across formats. Check the lens specs section of this site where there is a discussion of these differences. On the print, of course, odds are that LF is likely to have an advantage, thanks to lower enlargements required (given that the human eye can resolve somewhere in the region of 8 lppm, for an 8x10 print with a perfect enlargement system, an 8x10 format would need to deliver about 8 lppm to film, a 4x5 would need to deliver about 16 lppm to film and a 35mm would probably need to deliver about 64 lppm to film). And no enlargement system is perfect. I have not actually seen test results but am pretty sure that you do see greater losses with greater enlargement ratios, and this may well be non- linear. Even taking into account the fact that smaller formats may allow greater enlargements, this renders a huge advantage to LF.
Also, at some point, considerations of grain are going to set in.
There is reference on this site (I think its under the film holders section) to some work by Joe Englander where he found that Quickloads and Readyloads trail in sharpness compared to cut film holders and grafmatics (tolerances seem looser which means the film is not positioned at the same spot the ground glass was). However, I doubt that this would be a source of huge sharpness differences.
However, lets take a closer look at your set up. Firstly, you probably should do a direct comparison i.e., shoot the same subject in both formats you're comparing. With an 8X loupe, your eye is probably going to be able to resolve around 64 lppm or thereabouts (you might have some losses to imperfections in your loupe) on your film. If you look at the lens specs, you should find that your lens is capable of delivering that level of resolution, which might make it worthwhile for you test the alignment of your GG/film. You should find other discussion on that in the Q&A section of this site. Shoot a stack of slightly staggered playing cards or the like (so each card is slightly in front of the other) at a fairly large magnification.
Keep in mind that if you used a high enough power loupe, you may well find a point where the results from a smaller format look sharper through a loupe but this will of course never get transferred to the print (due to the factors discussed above). In other words, even using a lens/film combination of lower resolving power in Lf should render you advantages on the print compared to a lens/film combination of higher resolution in a smaller format.
Hope this helps. DJ
-- N Dhananjay (firstname.lastname@example.org), January 16, 2000.
What kind of tripod and head? Was the wind blowing? Did you "lock- down" all adjustments? Simple questions I know, but problems often have obvious answers. Never used quickload - so no comment on that. Once you get past f/16-f/22 lens performance will degrade rapidly, try to use swings and tilt to keep as close to these apertures as possible. At f/45 you would be lucky to get over 30lpmm on film under ideal conditions - add in field conditions, and the quickload filmholders, and that number is probably unobtainable most of the time.
-- Wayne DeWitt (email@example.com), January 16, 2000.
Forgot to add. Another thing to keep in mind when comparing formats is that there might be a difference on film in terms of DOF etc due to the differences in focal lengths. Compare two formats (say 8x10 and 4x5). You use a lens of twice the focal length on the larger format for the same framing. So, at the same f stop, the smaller format might have an advantage in terms of DOF on film, which of course, it loses in the course of enlargement, when the circles of confusion are enlarged to a greater degree.
Have some idea about the largest print you will make and use a loupe of about that power when you're checking focus etc. With 4x5, I generally think about 16x20 is the largest I will ever go and so I use a 4x loupe.
-- N Dhananjay (firstname.lastname@example.org), January 16, 2000.
Danny, if you shoot f/32 or f/45 using your 35 and 6x7 equipment, would they be sharper??? I think you may just be diffraction limited. Congratulations on getting you Wisner PE - I have one too ...
-- Carlos Co (email@example.com), January 16, 2000.
Thanks for your responses so far! I appreciate them all. A few further notes from this end...
I'm using the same setup as I use for smaller format, i.e. Gitzo 1227 carbon fibre tripod and Arca B1 ball head with RRS plate. There was no wind at all that morning, and I waited for everything to settle after inserting the film holder, before clicking the shutter. All the controls were firmly locked down. My shots don't have the look that I've gotten on handheld shots with 6x7 (OK, I should have used a tripod on those!), i.e. "elongation" of points. The 4x5 shots just have an overall "less sharp" look - and this is the same on the whole shot, not sharp/less sharp from one area to another.
I'll have to try a shot @ f/16 and see what happens. I was under the impression that one can use smaller f-stops as the format size increases, e.g. f/16 on 35mm vs f/22 on 6x7 vs f/32 on 4x5, and not experience loss of sharpness due to diffraction. Perhaps I misunderstood this...maybe that reference meant relative to print enlargement size rather than absolute quality of a certain area of film under a loupe? John Fielder's "Photographing the Landscape" says that one can stop down to f/90 without loss of sharpness. I thought that sounded a bit much, but without previous LF experience, I could only take him at his word! My 6x7 shots, just for comparison, are typically at f/16 or f/22 with excellent results.
-- Danny Burk (firstname.lastname@example.org), January 16, 2000.
Danny: At f/32, diffraction isn't much of a problem since diffraction limit at f/32 is still about 50 lp/mm. I don't worry about diffraction unless I go beyond f/45. I've measured on film (Provia) resolution of over 50 lp/mm with a 75mm Rodenstock Grandagon, and would suspect that the Fujinon 300C should be able to do at least 40- 50 lp/mm at that aperture. At that aperture, QuickLoad will not be a problem, assuming nothing is wrong with your holder. Some of my sharpest images have been with a 300mm Nikkor and QL holder. While the Mamiya, af f/16, can probably hit 60 lp/mm or higher, that's not a significant difference. I think the larger size of details in the larger chrome may suggest lack of fine detail. Until you do a side by side with same film, light and subject, it's hard to know if there is really a problem.
-- Glenn C. Kroeger (email@example.com), January 16, 2000.
Though I would add another story here... I did the following test:
120 roll film with 120mm Apo-Symmar at f/16 with Velvia 4x5 Velvia QL with 180mm Fujinon A at f/22+1/3 (since factor of 1.5 in focal length yields 1 1/3 stop less depth of field)
The 120 may have slightly higher on-film resolution, but it is outweighed by the difference of 1.5x in image size. On distant very fine scale detail (ribbing in tin roofs and bare tree branches) the 4x5 shows more actual image detail (but not much!)
Since tests show the apo-symmar is diffraction limited at this aperture in center of the field, I doubt Mamiya7 lenses would be much different.
-- Glenn C. Kroeger (firstname.lastname@example.org), January 16, 2000.
At f32 and f45 you might be losing a small amount of resolution from diffraction. What size prints are you planning? One can be appalled at almost any negative when examined at very high magnification. If the negatives look good with your 3.6X loupe, you will probably get excellent prints upto at least 16X20.
If I remember the equations rightly, comparing diffraction effects across formats (negative sizes) for the SAME SIZE PRINTS, then if you double the size of the negative, the same diffraction obtains at one stop further stopped down. So f8 on 35 mm is about the same as f11 on 6x7 which is about the same as f22 on 4x5.
If you suspect a film plane vs ground glass problem, an easy test would be to photograph trees at a range of distances. This may already be present in the photographs you are describing. If some trees are sharply focused, but they are not the ones you focused on, then the problem is identified.
-- Michael Briggs (MichaelBriggs@earthlink.net), January 16, 2000.
Michael: not quite right. For the SAME SIZE PRINTS, then if you double the size of the negative, the same diffraction obtains at double the f-number. So f8 on 35 mm is about the same as f16 on 6x7 which is about the same as f32 on 4x5.
I don't know Astia, QL, or that lens, so I don't know which of these would be dominant in softness. Danny describes the LF as 'quite a lot softer' than MF, which I don't think should be the case. As he is directly comparing on-film resolutions, rather than same-size prints, we might expect them to be slightly softer (because larger format lenses typically have lightly lower resolutions), but not much.
-- Alan Gibson (Alan.Gibson@technologist.com), January 16, 2000.
Danny, First I would check the mechanics: Was the lens assembled correctly afeter being mounted? Does the GG line up with the silm plane in your holder? Is either out of spec? Have you trired with a different holder. iuse QL all the time and have tested my QL holders against a variety of differnt holders and found therewas virtually almost no difference with my cameras (Canham DLC & Arca Swiss 4x5 F-line.) with the lens (a 210mm f/5.6 Nikkor W) wide open and no difference with with the lens stopped down to f/16 and f/22. The test were made on Velvia QL and Velvia 4x5. Your images should be sharp. Something in your imaging system: either your camera, your holder or the combination of the two, is wrong.
-- Ellis Vener (email@example.com), January 16, 2000.
There has been many qualified responses above that all point to potential problems in the mechanics of the process... I agree with all of them - and you should confirm these are / are not issues in your paticular situation. It sounds as if you are astute enough to know if one of these problems exists, but many of us have been fooled before.... However, I must admit I continue to share the exact same frustration you are experiencing. I own a Mamiya 7, 4x5 and 8x10 cameras. Unfortunatly you started comparing your 4x5 work to one of the sharpest camera systems in the world...The bottom line is this... the M7 lenses are probably the sharpest lenses ever made. Some test results have recorded 140 lpmm to film! This is truly amazing, considering the very best 4x5 lens will offer maybe 75 lpmm... mainly the very new Schneider Super Symar XL 150 and 110mm. But, apart from this lens and a select few others, most LF lenses are far inferior. The Nikor 300M you used - I once saw it recorded at approx. 50 lpmm. Still not high enough to overcome the magnifcation degredation that will occur bringing the 6x7 chrome to 4x5. From my experiences with these same cameras, I have concluded that the M7 produces 11x14 (sometimes 16 x 20) prints as good as 4x5, unless I am using my Super Symar XL's, in which case the 4x5 will produce slightly better results. Of course there is many other issues regarding lenses that equate to high quality enlargements, resolution being only one of them. However, I am somewhat convinced it is very significant in this comparison you are making. After a year of using these cameras, I still am baffled how my M7 chromes out perform my 4x5 chromes. (BTW, I doubt the QL are the problem, specially if stoped down to f22 or 32, I have tested them against film holders and rarely notice a difference, Depth of focus overcomes a lot of mis alignment at the film plane at those apt. - do the math and you will see) I have now come to accept this fact and have changed my shooting method as follows... If I have the right fl lens for the M7 for proper compostion, I use that camera first... unless the shot requires movements, then I use 4x5. If the scene is so awesome, or I envision a very large print (larger than 24"), then I use the 8x10 camera. And that jump becomes truly amazing, specially when using the high res. Super symars on 8x10. Both the 4x5 and M7 pale in comparison to these 8x10 chromes. So, assuming you have no mechanical issues, then IHHO, this situation will continue to amaze you for many years. After a shoot, I still stare at my M7 chromes under a 8x loupe and marvel at the sharpness and color rendition these chromes have compared to my 4x5 chromes! Now, if only Mamiya had longer lenses available for this format..... well that is the downer, they never will... they final introduced their longest lens, a 210mm f8...its huge and very slow. So although this amazing camera system produces results unparalled to anything I have seen, as with all things in photography, it still has has a down side... very limited fl's...and no movements. (Remember, this camera is the perfect wedding camera, that is what its intent was) If the M7 had the ability of long fl's, all movements, auto foucs, auto wind, TTL flash metering... I would sell all my LF equipment and use this camera system exclusevely! But that won't happen, so back to LF! I hope this adds some light to your situation.... Take Care....
-- Bill Glickman (firstname.lastname@example.org), January 17, 2000.
At f45 you will get noticable softening due to diffraction. I try to make this my max stop down. Comparing to medium format, you should try to stay around f22. Another thought is the extra coverage of the 300mm lens may be causing some flare and loss of contrast from the extra non-image forming light bouncing around inside the camera. Use a hood. Comparing my APO Sironar S 150 with my Fuji GW690 90mm lens, I don't see any loss of sharpness going from medium to 4X5. I do see a softening at f45 though. Do more testing and maybe try another lens. I have a Fuji 240 f9 A that is an excellent performer but not quite as good as the APO Sironar S. It will cover 8X10 so using a hood helps improve contrast in many situations. I also use a QL holder, as well as standard holders, and have not had any problem with it.
-- Gary Frost (email@example.com), January 17, 2000.
Bill's post brings up another important issue... film. It may be that at f/8, Mamiya 7 lenses can resolve 140 lp/mm, but NOT on color film. Look at the MTF curves for Velvia and Provia F. By 50 lp/mm these films are very low contrast. This is not to say that they cannot resolve more lp, but you will see soft separated lines, not crisp edges... the film just doesn't have the high frequency response to render this fine detail crisply. So 4x5 buys you a 50% linear size increase over 6x7. Even if you can get medium format lenses that resolve more than 50% better than 4x5, that's unlikely to occur at the f stops normally used in landscape work, where lenses in both formats are diffraction limited. Consider shooting at f/16 on your 6x7. Diffraction limits resolution to about 90 lp/mm but Velvia cannot record that (at real world contrast ratios). For equivalent depth of field, you would shoot the 4x5 lens (assuming a 1.5 ratio of focal lengths) at about f/24 (22+1/3) with a diffraction limit of about 60 lp/mm which Velvia CAN record. So the 4x5 will still hold an edge in detail, but barely.
The real question is whether the extra detail in 4x5 is usable! With digital enlargement (Tango scanner, LightJet 5000) about the maximum usable scanning density is 150 pixels/mm or 3800 ppi. That corresponds to a maximum resolution of 75 lp/mm. I've run tests with identical images, and with careful application of unsharp masking, there is virtually no difference in DETAIL in 20x24 inch prints from 6x7 and 4x5. There IS a difference in grain and tonal smoothness in areas of smoothly varying tone such as sky.
So the bottom line is not to expect TOO much from 4x5. It is slightly better than 6x7 in capturing detail given real film and lenses. But that slight edge is not going to show up, in color photography, in 16x20 or smaller prints if you use the best digital enlargement techniques. If you use traditional printing, there will be some difference in a 16x20 print. The big advantage of sheet film is the ability to push or pull process individual sheets, and the ability to crop with abandon and still make wonderful 20x24 prints. And on the light table, 4x5 chromes are more satisfying than 6x7.
-- Glenn C. Kroeger (firstname.lastname@example.org), January 17, 2000.
This is a reply to Bill Glickman's comments:
In my experience, resolutions higher than about 60 lp/mm are pretty much mythical beasts in ANY film format. One reason already pointed out is the resolution of the film itself. A second is the fact that diffraction typically ends up limiting you to far less.
Let's look at that "140 lp/mm" Mamiya lens that Bill raves about as an example: Simple theory and a bit of math tells us that such resolution is only obtainable at apertures of f/4.5 or wider even if the lens is otherwise perfect in all respects. By f/8 you're limited by diffraction alone to about 85 lp/mm, and at f/22 (a reasonable opening for near-far lanscape shots in 6x7) you're limited to 57 lp/mm. All of a sudden the pathetic-sounding 50 lp/mm resolution of that Nikkor M (or Danny's Fuji, which is a pretty similar lens) begins to look like it might really be a non-issue after all. At the f/45 opening that Danny used in his test, the diffraction-induced resolution limit is about 30 lp/mm. He'd might as well have been using a Wollensack or a polished Coke-bottle bottom at that point.
Furthermore, the human eye is only sensitive to spatial frequencies out to about 7 lp/mm (and even that's rather optimistic for anybody over age 30), so I seriously question Bill's ability to perceive anything past ~50 lp/mm through an 8X loupe. I know I can't (I've tested myself and others using targets of known frequencies as part of my job).
Bill, if you can see a significant difference between your 6x7 chromes and 4x5's shot with lenses as good as the Super Symmar under an 8X loupe, then I respectfully submit that there is something wrong with either your equipment or your technique. Well-executed LF work with top-notch lenses at ideal apertures should be nearly indistinguishable from perfection under magnification that weak, so no matter how good the Mamiya system is, the differences shouldn't be anywhere near as dramatic as you imply. Critical examination under a quality microscope might be another story altogether, of course...
-- Patrick Chase (email@example.com), January 17, 2000.
Bill, the camera you want is the Fuji 680 III. No rear movements, but ample front standard movements for a plethora of lenses from about 55mm to 500mm. And because the film format is 6x8 cm it is an even better match if you are trying to fill every last mm of an 8x10 or 11x14 piece of paper. And the lenses are, in my opinion, better than the Mamiya lenses for the RZ67 cameras.
-- Ellis Vener (firstname.lastname@example.org), January 17, 2000.
Ellis, I agree with you comment about Fuji 680 III, it is the only MF camera system that resembles LF. Two things prevented me from going with that system, the first is the size of camera and lenses, they are huge...the camera body is way bigger than my 4x5 body and also is not back pack friendly. The other reason was the poor lens resolution test results that were done by C. Perez, linked to this page. But I did take a good hard look at it...
As for the Mamiya 7 chromes vs. the 4x5 chromes, I respectfuly agree with most of the comments above. Being anal, I had to go re check my chromes after the above threads... and although I do not claim to be quite as scientific in my approach as some of the very knowlegable posters, I will say this for certaninty, and I know it somewhat defy's the math above... My M7 chromes withstand a 16x loupe with no loss of sharpness, and yes, most were shot at f8....although grain does become a slight issue at 16x, I will concede that, but I am hoping photoshop can clean the grain issue up. Now, my 4x5 chromes, none withstood the scrutiny of 16x, my best shots with the Super Symar XL's and some with the fuji 240 f9 mentioned above (the best lens I have next to the SS XL's) will withstand about 10x, my other LF lenses such as Nikor 75mm, Nikor 360W, Nikor 450M, were in the 6-8x. These are averages based on several hundred chromes. Of course there is exceptions to everything, these are AVERAGES. I did this to help express what is going on with my camera and lenses, not to offend anyones camera system or lenses.
I only use Velvia film, considering its high resolving power compared to other color films, this may be the reason the difference is apparent. I have to admit, this has been, and still is quite surprising to me - so Danny I fully appreciate you amazement. As one poster suggested, we have to be careful not to ask tooooo much from 4x5. I fully agree with that statement... Of course the 8x10 chromes withstood the same loupe magnification as the 4x5, but with double the format size, it just beats everything, including my back and shoulders! I welcome anyones comments, until this thread, I finally came to the conclusion as well as other Professional Photograhpers that informed me of the M7's amazing lenses... this is just the way it is.... nothing is wrong... I have performed gg/film alignment test so many times, I am convinced they cameras are right on the money. Also all of my LF cameras are brand new Toyo's, and all use new toyo film holders. I have done everything possible to rule out any error prone areas in both technique and camera mechanical operation...
-- Bill Glickman (email@example.com), January 17, 2000.
Actually, MF may score over LF even in the area of film alignment. Many (if not all) MF cameras have a pressure plate to hold the film flat - something which isn't done with LF (barring expensive vacuum backs). The larger film size of LF also perhaps contributes to the film bowing out of GG position. So even with a GG in the right place, you can have alignment issues.
I don't think comparing resolutions across formats is going to be frightfully conclusive - just far too many variables involved (aspect ratios, focal length differences which contribute DOF on film, different apertures one typically shots at which affects both DOF as well as sets resolution limits due to diffraction). And all of this still doesn't take into consideration the fact that an enlargement system will bring its own set of idiosyncracies (including diffraction) to bear.
The biggest draw for me to LF (at least in terms of sharpness, for the moment leaving aside advantages due to movements and grain and contact printing) is the fact that enlarging losses do seem to get worse with larger enlargement ratios, especially with real enlarging systems. In other words, I suspect that loss of sharpness is not linear. So if you have 100 lppm on film, a 2X enlargement may give you a loss of 50 lppm + another say 5 lppm due to enlarging system inperfections, leaving you with about 45 lppm. A 4X enlargement however is not a linear extrapolation of this i.e., it is not just a loss of 75 lppm to enlargement + another 5 lppm to the enlargement system imperfections. Your losses to the enlargement system add up too and thus you lose not just 75+5 lppm but a greater amount. Most of the time, enlargement systems are diffraction limited, especially once you get to large enlargement ratios. A long distance from lens to paper means smaller effective apertures, more distance for light rays to bend and bounce around the place etc. Thus the preference for smaller enlargement ratios => larger initial negs to begin with. However, please bear in mind that I am just speculating at this point. I have not actually seen tests (nor, needless to say, have I attempted them). Food for thought....
In any case, there's many more qualities to a photograph than lppm. I mean, pictures from ages past probably used lenses of even more limited sharpness. Doesn't seem to diminsih their appeal.
-- N Dhananjay (firstname.lastname@example.org), January 17, 2000.
Thanks for the outpouring of time and effort to my question! I really do appreciate every one of your responses, and would like to reply to some of the points that have been raised.
First of all, I spoke to Ron Wisner this morning. I sent him the 2 4x5 chromes in question, and he examined them upon receipt today. He confirmed that they should indeed be considerably sharper than they are, regardless of having shot them at f/32 and f/45, and asked several questions that could have affected their quality, i.e. did I use any type of filter (no) and other points that I covered in my earlier posts to this column. He asked me to take a test shot using another lens, with the suggestion that my Fuji 300mm could be defective. His comment was that the softness looked like that caused by diffraction that would occur at a much smaller aperture than I used, e.g. f/64 or smaller, but specifically *didn't* think that f/32 or 45 would cause so soft an image. Ron also suggests that smaller format shots with a high-quality lens will indeed surpass one on LF *in terms of absolute picture area* - i.e. cut out a 6x7 piece of a 4x5 chrome, both shot with the same fl and f/stop, and compare them directly - but that the 6x7's quality shouldn't be only slightly superior rather than a vast amount.
Over lunch hour today, I did a simple test shot of trees with a lot of small twigs in my back yard. I used a different lens - 150mm Super Symmar XL, which should certainly give the sharpest possible image, which this time I shot at f/16 on Velvia Quickload. I focused very carefully and rechecked focus after removing the QL holder - all was still as it should be. I should have the film back from the lab on Wednesday, at which point I'll examine it closely and report my findings in this column and to Ron Wisner. If it's indeed a lot sharper, I'll believe that Ron's theory of a defective lens may be correct, and will take up his offer to send the lens to him for testing.
Following up on some posts to this column...
I'm not planning at the moment to make prints of my shots. In smaller format I shoot only transparency film, and am doing likewise on 4x5. At some point, I may buy some negative film just to have it on hand if I foresee "something special" coming up. Enlarged print size is therefore not something that affects me at this time, but I can observe similar effects by viewing my chromes with 8x vs 3.6x loupes.
Ellis - I haven't tried a different QL holder (or any other holder for that matter), simply because this is the only holder I presently have. If today's test shot also turns out soft, I'll have to think that the holder may be at least partly at fault.
Bill - I'm intrigued by your comments re: Mamiya 7 vs LF. I will have to try shooting some negative on each (which I've never done), just out of curiosity, and compare same-size resulting enlargements, once this LF soft-focus problem is resolved! I could have compared an area of one of my 35mm shots for sharpness with the 8x loupe instead, but I used 6x7 simply because the format was closer in size, for whatever that's worth.
I'll keep everyone posted as the saga continues...thanks again for your interest :)
-- Danny Burk (email@example.com), January 17, 2000.
Glad you are making progress. Two thing I thought I would add. If your Fujinon 300C is at fault, it is not a problem with all Fujinon 300C. I have owned both a Nikkor 300M and a Fujinon 300C and found them both to be very sharp. If anything, my Fujinon was a bit more contrasty than my Nikkor, although I never tested resolution.
Second, I would agree with one of the previous posts that flare from the large image circle is a real issue. I know many LF photographers that insist that shading the lens with their hat or dark slide is enough. But for color work, a good bellows lens shade really improves image contrast, and therefore the impression of sharpness. MF and 35mm lenses today have flare baffles built into their designs, but with LF you have to do it the old fasioned way with an adjustable hood. Now that Lee makes several versions of their self supporting bellows hoods, including ones that fit Cokin holders, it is pretty easy to deal with a lightweight adjustable hood.
Let us know how this turns out!
-- Glenn C. Kroeger (firstname.lastname@example.org), January 17, 2000.
Danny, you sure did start a popular thread! The only other item I think was missed, and it seems we nailed them all, great contributions... the part of the image circle you are capturing in your film is very important also. If you are at the edge of the image circle, you can find very significant sharpness fall off. In the tests done by C. Perez, many of the edges fall offs can be 50%! And his test was only testing the edge of the film, not the edge of the image circle! It gets worse! This is very significant if the best part of the lens is only delivering 50 lpmm. The other related issue I would mention is this... for some reason, some lenses have f stop "sweet spots" that resolve excellent in comparison to the other f stops. My Fuji 600C shoots very poor at f11... If you look at the tests by C. Perez linked to this home page, you will see exactly what I am talking about. We are all interested to hear what Ron Wisner says also, he sure is a good resorice for this information. Since you already bought a camera from him, you can be assured his response will be non biased. Thank you for sharing on this thread...
-- Bill Glickman (email@example.com), January 17, 2000.
Check out this site for a lot of useful info on large format lenses: http://www.hevanet.com/cperez/index.html Check out the lens tests, and especially the heading 'How to determine usable/meaningful resolution limits'.
-- Ron Shaw (firstname.lastname@example.org), January 18, 2000.
One apology/clarification: Glenn Kroeger rightly points out that I got my estimates of diffraction-limited resolution wrong. Specifically, I used a relation (the Rayleigh criterion) which is specific to resolvability of adjacent point sources, and the way I used it to estimate the continuous (i.e. non-point sorce) case of an MTF target was very pessimistic. All that I'm really sure of now is that the real diffraction-limited resolution numbers are somewhere between what I posted and double what I posted.
Sorry about the confusion!
-- Patrick Chase (email@example.com), January 18, 2000.
Hello again! I'm back with interesting news to report. Today I picked up my test shot of trees/twigs shot with the Schneider 150mm Super Symmar XL. And...it's *very* sharp. Detail of tree bark and individual twigs can easily be seen with the 8x loupe. I didn't do any simultaneous shots with the Mamiya 7, so it's difficult to make a precise comparison based on non-identical subjects...but I'd have to say that it is only a *slight* amount less sharp than my Mamiya 6x7 chromes.
So...right now it looks like the Fuji 300mm lens is the likely culprit. I'm sending it to Ron Wisner for testing per his offer, and will await the results. Has anyone here gotten a brand-new major- brand lens that proved to have poor focus or other technical problems? Just bad beginner's luck, maybe? :)
I'll post additional info when I know more about the lens. Thanks again and happy shooting!
-- Danny Burk (firstname.lastname@example.org), January 19, 2000.
Don't rule out instability as a possible culprit. The 300mm requires 2x more bellows than the 150mm, wind or balance may have been a factor. I would have tested the lens with flash before sending it back.
-- Wayne DeWitt (email@example.com), January 20, 2000.