xenohip
Established
One more note on the image quality invariance: DOF scales according to the absolute physical dimension of the aperture, for a given angle of view. The 40mm lens at f4 on 35mm format and the 80mm lens at f8 on medium format both have an aperture dimension of 10mm diameter (at least in simple, if not compound, lens terms). Therefore both lenses gather the same amount of light per unit time. If the ISO of the capture medium is adjusted to equalize the shutter speeds (i.e. 100 ISO 135 = 400 ISO 120) then the two images are formed from an equal number of photons. It makes good sense that the image quality would be similar.
semilog
curmudgeonly optimist
ok, just to make a fool of myself, I tried to play with numbers I don't understand,namely film RMS.
Tmax 100 is announced at RMS=8, while TX is 17.
a 6x9 neg requires ~2.5 less enlargement than a 35mm frame, thus it seems that in terms of grain effects, a TX on 6x9 has much more grain than a tmax 100 frame in 35mm (each RMS unit multiplies whatever is measured in the grain by a factor of two, right?)
Now that I have made clear that I understand nothing about that stuff, can someone correct me so we learn something today?
Note that RMS is a measure of grain, not resolving power.
For resolution you need to look at the film's MTF data. TMAX100 is indeed spectactular, Fuji ACROS is equivalent, and I'd venture to guess that Delta 100 is right in there with the others. Assuming that the camera is held stable and shutter/mirror movement are well-damped, the next most important cause of image blur is usually inaccurate focus. After that, it's film flatness. 35mm generally does better than MF for flatness, which helps 35 to close some (but not all) of the gap with MF. Another thing that can wreck 35mm sharpness is overexposure/overdevelopment. Thin negatives are generally sharper. This is often overlooked.
Assuming you've got all of that under control, you then need to get the detail back out of the negative. It's a lot easier to get good enlargements from MF negatives than from 35mm, but with good gear and technique it can be done. Holding the film flat is critical. I love the half-glass carrier for the V35 enlarger.
If you're scanning, MF wins again, and in a big way.
Really it's at the enlarging/scanning stage where MF has the biggest advantages. But 35 can be awfully good with exacting technique. Here's one of my better examples: ACROS developed in XTOL 1+1, scanned on a Polaroid 4000. Click on the picture to see bigger versions of same. Note that scanning tends to accentuate grain vs. enlargements, one reason why MF scans look better than 35. A drum scan would be better, and a good enlargement better still. Even so there is a lot of detail in this image.
My impression of carefully-handled ACROS is that it can approach the quality of Tri-X or HP5 shot on 645 format. TMAX400-2 on 645 would probably be superior. Soon I'll be out of Neopan 400, and ACROS and TMAX400-2 will be my exclusive choices for 35mm B&W.
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Denton
Established
My simplistic understanding
My simplistic understanding
On reflection, someone's head projected onto the film plane with an 80mm lens is the same whether it's MF or 35mm film. The film and image are the same as well as the DOF if the subject-lens distance does not change. But, I need to get half the distance with MF to fill the frame to the same degree, so that's the difference. I can ignore most of the math.
The critical thing is how large, in real dimensions, will the image take on the film plane.
My simplistic understanding
On reflection, someone's head projected onto the film plane with an 80mm lens is the same whether it's MF or 35mm film. The film and image are the same as well as the DOF if the subject-lens distance does not change. But, I need to get half the distance with MF to fill the frame to the same degree, so that's the difference. I can ignore most of the math.
The critical thing is how large, in real dimensions, will the image take on the film plane.
sanmich
Veteran
Isn't the grain size the only thing limiting the actual image resolution on the film?
A lot of detail in this shot indeed.
handheld?
RF or SLR?
semilog
curmudgeonly optimist
No, because the specific way in which the grain clumps has huge effects on both resolution and perceived sharpness. That's why Kodak and Fuji provide information about both grain (RMS) and modulation transfer (related to resolution). There's a big literature on this subject. For digital cameras, Falk Lumo has written a beautiful and terse (though somewhat technical) summary of what image sharpness is. The bottom line is that edge effects added by either signal processing or film chemistry and grain geometry (which should be seen as a form of signal processing) can alter both the MTF response and the perceived sharpness.
Kodachrome was sort of a poster child for edge effects that gave it very high resolution and extremely high perceived sharpness despite having more grain than some competing slide and negative films. This is a major reason why I loved Kodachrome.
Here's an example of huge grain and high perceived sharpness: Delta 3200, exposed and then forgotten in a box stored in an attic for over ten years, then developed in XTOL. Again, click for bigger versions.
See also the Wikipedia entry for acutance.
Handheld M6 and 35/2.8 C Biogon. Probably f/5.6 or 6.3 at 1/1000 on a very bright, clear summer day in central California.
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Turtle
Veteran
120 (6x7) TriX or HP5 is grainless on a 8x10 and I would roughly say that both can be broadly comparable to a fine grained 100 film, like D100. I prefer the look of the former most of the time, however. A 'lowly stressed' big neg from an old emulsion always seems to look better to my eyes than the ultra low grain films. I just dont like modern films much.
Also, the comment earlier about 120 film having more exposure latitude confused me. I don't find this to be true at all - they are the same if the enlargement factor is the same. In terms of what ends up on film, there is no difference that I have noticed.
Also, the comment earlier about 120 film having more exposure latitude confused me. I don't find this to be true at all - they are the same if the enlargement factor is the same. In terms of what ends up on film, there is no difference that I have noticed.
pvdhaar
Peter
When the enlargement factor is the same, then you're absolutely right. It's just that you don't have to enlarge 120 the same amount to get to a specific print size. And there lies the catch. The lower magnification factor required means that especially shadow areas remain cleaner..
Turtle
Veteran
I'm still not sure I agree with you or understand how this can be so. Shadow areas surely respond no differently in any format and even tho 120 is enlarged less, I do not see what qualitative effect this has on shadows in the context of latitute. If they are overexposed they are printed down, if under, they are going to look bad regardless of format, surely?