Arjay
Time Traveller
Having come back to analog from digital photography, I' going through a number of picture processing woes that some of you might know:
At first glance, most of my scanned negatives seem to be slightly defocussed. It's really maddening. But let me explain in more detail:
I recall that the conventional COC value for 35mm film is around 0.033mm. Considering that scanning a film with 4000dpi and viewing it on-screen at 100% corresponds to a very substantial magnification, which COC value should I use for my shooting practice? Suggestions anyone?
PS I use a Konica Hexar RF w/ 35mm and 50mm Hexanon lenses.
At first glance, most of my scanned negatives seem to be slightly defocussed. It's really maddening. But let me explain in more detail:
- I use zone focusing and take my lenses DOF scale as reference (as well as DOF slide rules - google DOFMaster). I'm using Kodak BW400CN chromogenic BW film for now. Using such a fast film in daylight conditions ensures that I practically always have a shutter speed that precludes blur due to camera shake.
- I am scanning my negatives using a Nikon Coolscan V ED at 4000 dpi. That's a fairly high resolution, and this may be part of my problem.
- When I view my scans on my computer screen at 100%, it is very often quite a sobering experience: It appears that none of my shots are really sharp over the desired DOF distance range.
I recall that the conventional COC value for 35mm film is around 0.033mm. Considering that scanning a film with 4000dpi and viewing it on-screen at 100% corresponds to a very substantial magnification, which COC value should I use for my shooting practice? Suggestions anyone?
PS I use a Konica Hexar RF w/ 35mm and 50mm Hexanon lenses.
ferider
Veteran
The math is pretty straight forward:
The standard 30 microns COC for 35mm film refers to an enlargement on 8x10, viewed from 1 foot (http://www.bobatkins.com/photography/technical/dofcalc.html).
A computer screen has typically 72 dpi. Not sure how close to your screen you are. We need the distance for COC translation.
I were you, I'd rather use a decent print size and 200-300 dpi for reference, depending on what is still OK for you.
Roland.
The standard 30 microns COC for 35mm film refers to an enlargement on 8x10, viewed from 1 foot (http://www.bobatkins.com/photography/technical/dofcalc.html).
A computer screen has typically 72 dpi. Not sure how close to your screen you are. We need the distance for COC translation.
I were you, I'd rather use a decent print size and 200-300 dpi for reference, depending on what is still OK for you.
Roland.
john_s
Well-known
I use the DoF marks on the lens barrel for two stops wider than the aperture I'm shooting if I need lots of DoF. The actual focused distance will still be sharper than the rest of the DoF, so if there's something very important in the scene I would tend to focus on that distance (e.g. one person).
The standard DoF was historically set at around a postcard sized print on 1930s film.
There are several mathematical approaches to calculating an optimum CoC. It seems to me that we expect sharper results than these methods suggest. Maybe we look too closely. Maybe we're spoiled by the exceptional sharpness of modern lenses and films, which can make unfocused areas more conspicuous.
We tend to learn this the hard way. I did too.
The standard DoF was historically set at around a postcard sized print on 1930s film.
There are several mathematical approaches to calculating an optimum CoC. It seems to me that we expect sharper results than these methods suggest. Maybe we look too closely. Maybe we're spoiled by the exceptional sharpness of modern lenses and films, which can make unfocused areas more conspicuous.
We tend to learn this the hard way. I did too.
fensantu22
Newbie
It seems to me that we expect sharper results than these methods suggest.
pvdhaar
Peter
When using the DOF markings on a lens, the results are often a bit of a disappointment indeed.. Instead of getting a zone of sharp focus, my attention is mostly drawn to the region where stuff of interest is becoming fuzzy.
So I've learned that for scale focussing on subjects nearby, I have to stop down 1.5 to 2 stops further than the DOF markings suggest. And still I need to set the focus in the ballpark range of where the subject is..
Another thing that doesn't work as advertised is the hyperfocal technique for landscapes, where you align the infinity symbol with the aperture chosen, and expect the whole image to be sharp from near to far. What you get is a just off-sharp horizon that's extremely distracting. So when it comes to landscapes, I set focus to infinity, and set aperture to f16. This gives a better distribution of sharpness throughout the image.
So I've learned that for scale focussing on subjects nearby, I have to stop down 1.5 to 2 stops further than the DOF markings suggest. And still I need to set the focus in the ballpark range of where the subject is..
Another thing that doesn't work as advertised is the hyperfocal technique for landscapes, where you align the infinity symbol with the aperture chosen, and expect the whole image to be sharp from near to far. What you get is a just off-sharp horizon that's extremely distracting. So when it comes to landscapes, I set focus to infinity, and set aperture to f16. This gives a better distribution of sharpness throughout the image.
Roger Hicks
Veteran
Dear Peter,
Depends on the lens, too: not all manufacturers' d-o-f scales agree. I generally go one stop down with my Leica lenses.
For landscapes, I'm inclined to agree, though I'll sometimes set just 'off' infinity: infinity against f/2.8 or 4, perhaps, when shooting at 11 or 16.
Cheers,
R.
TomN
Established
DOF scales on lenses are outdated. This is something that Zeiss have admitted, as it is a common complaint. If you use DOF scales for hyperfocusing for example, you can expect results based on 1920's emulstions and non coated glass. Here are some expamples that I shot last week where I focused one photo at hyperfocal, and the other at infinity. the lens size used was about 3.5mm for both shots. These shots are untouched and unsharpened with no noise reduction. development was in diafine.
INFINITY
HYPERFOCAL
INFINITY FOREGROUND
HYPERFOCAL FOREGROUND
INFINITY MIDGROUND
HYPERFOCAL MIDGROUND
INFINITY BACKGROUND
HYPERFOCAL BACKGROUND
The inifinty shot has clearly more depth of field, and whilst not quite as sharp in the foreground, it renders everything that I wanted (the tombstone main writing). I could have stopped down one extra stop which would have yielded a slightly sharper foreground, but at the expense of a diffraction limited backgound. as the foreground was acceptable, i decided to stick to f9.5 on my 35mm lens. The silo in the background is rendered about the same in both images, so at this distance diffraction is now limiting what I can render.
INFINITY
HYPERFOCAL
INFINITY FOREGROUND
HYPERFOCAL FOREGROUND
INFINITY MIDGROUND
HYPERFOCAL MIDGROUND
INFINITY BACKGROUND
HYPERFOCAL BACKGROUND
The inifinty shot has clearly more depth of field, and whilst not quite as sharp in the foreground, it renders everything that I wanted (the tombstone main writing). I could have stopped down one extra stop which would have yielded a slightly sharper foreground, but at the expense of a diffraction limited backgound. as the foreground was acceptable, i decided to stick to f9.5 on my 35mm lens. The silo in the background is rendered about the same in both images, so at this distance diffraction is now limiting what I can render.
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Roger Hicks
Veteran
Dear Tom,
It's not so much the emulsions and the lack of coating, as the expectation of the size the print will be enlarged. Pre-war Zeiss d-o-f markings were reputedly based on postcard size enargements; Leica's, on whole-plate (6.5 x 8.5 inch).
Cheers,
R.
It's not so much the emulsions and the lack of coating, as the expectation of the size the print will be enlarged. Pre-war Zeiss d-o-f markings were reputedly based on postcard size enargements; Leica's, on whole-plate (6.5 x 8.5 inch).
Cheers,
R.
TomN
Established
that may be true, however Zeiss claim that they stick to the international DOF standard that all reputable lens makers use.
TomN
Established
nowadays, also very little traditional optical printing is done, so you don't tend to lose that bit of extra quality with an enlarging lens.
Al Kaplan
Veteran
You don't lose an extra bit of quality with an enlarging lens. If the image looks sharp in the print what did you lose?
Another consideration is the relationship between print size and viewing distance. We tend to look at larger images from a greater distance.
Another consideration is the relationship between print size and viewing distance. We tend to look at larger images from a greater distance.
Arjay
Time Traveller
Maybe it's that viewing habits change?
Maybe it's that viewing habits change?
Thank you for your enlightening contributions!
Agreed. There's no doubt that there is a correlation between print size and viewing distance (and in fact, this is also at the heart of any CoC calculation formula).
Only, if our viewing habits change, e.g. because we prefer bigger prints which we view from the same distance as before, then there will be a larger spectator's viewing angle, and in turn the minimum discernable detail will be smaller. This is exactly why I posed my question.
With ever-increasing print sizes in exhibitions and our habit of looking at image close-ups on screen, I feel that viewing habits are indeed changing.
So, it is my hunch that I really should generate my own DOF calculation rulers. The question remains - what new CoC-value should I use? Are all of you just working by rule of thumb?
Maybe it's that viewing habits change?
Thank you for your enlightening contributions!
Agreed. There's no doubt that there is a correlation between print size and viewing distance (and in fact, this is also at the heart of any CoC calculation formula).
Only, if our viewing habits change, e.g. because we prefer bigger prints which we view from the same distance as before, then there will be a larger spectator's viewing angle, and in turn the minimum discernable detail will be smaller. This is exactly why I posed my question.
With ever-increasing print sizes in exhibitions and our habit of looking at image close-ups on screen, I feel that viewing habits are indeed changing.
So, it is my hunch that I really should generate my own DOF calculation rulers. The question remains - what new CoC-value should I use? Are all of you just working by rule of thumb?
Steve M.
Veteran
Y'all have lost me with all this science. Just shoot MF if you want better enlargements and use a fine grained film. Stop down if you want better DOF. Open it up for portraits. Use the best lenses you can buy. Optical print if you want things sharp w/ your nose up to the print, as my experience is that the silver emulsion has smoother tonal graduations than ink sprayed on paper. It's IN the printing paper, not on top, and it's silver emulsion, not ink. Scanning does weird things to B&W film grain anyway, no matter what scanner you're using, even w/ drum scans.
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ferider
Veteran
Let me ask again: what enlargement and viewing distance do you target ? How do you print ? Who here could tell you what your goal is ?
For me personally, 8x10 and 1 foot viewing distance makes very much sense also today, since this is usable for albums, etc.
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jtzordon
clicking away
I've been happy with my results for 35mm printed at about 6x9 in image on 8x10 in paper. I generally use one aperture down, so if I'm shooting at f11 I use the f8 markings (on my Jupiter 8 lens). I only use the tables on the lens if I'm shooting something fast that doesn't give me enough time to focus, and so accept any compromises based upon the circumstances. If I have time, I focus on what I think is most important and let dof fall where it may.
Al Kaplan
Veteran
Jordan said it perfectly!