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Thread: LF resolution compared to smaller formats?

  1. #1

    Join Date
    Dec 1999
    Posts
    64

    LF resolution compared to smaller formats?

    Hi,

    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 wh at I wanted, and at first glance focus seemed perfect too. Under my 8x loupe, ho wever, the image resolution was a lot softer than I expected. With Toyo 3.6x lou pe, 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 sho t 1 sec @ f/32.5; second shot 1/2 sec @ f/45 (sun came out!). I focused VERY car efully using the Toyo loupe and darkcloth, and checked focus again after removin g 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 i s soft in comparison. So many of this forum's readers use QL, however, that I ca n't imagine the difference is that great.

    Am I expecting too much, or do I have a technical problem? My first thought is t hat 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!!

  2. #2

    Join Date
    Mar 1999
    Posts
    674

    LF resolution compared to smaller formats?

    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

  3. #3

    Join Date
    May 2006
    Posts
    376

    LF resolution compared to smaller formats?

    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.

  4. #4

    Join Date
    Mar 1999
    Posts
    674

    LF resolution compared to smaller formats?

    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.

    DJ

  5. #5

    Join Date
    Jan 1999
    Posts
    94

    LF resolution compared to smaller formats?

    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 ...

  6. #6

    Join Date
    Dec 1999
    Posts
    64

    LF resolution compared to smaller formats?

    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.

    Thanks again...Danny

  7. #7

    LF resolution compared to smaller formats?

    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.

  8. #8

    LF resolution compared to smaller formats?

    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.

  9. #9

    LF resolution compared to smaller formats?

    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.

  10. #10

    Join Date
    May 1998
    Posts
    218

    LF resolution compared to smaller formats?

    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.

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