smk@wxlvax.UUCP (Simon Kao) (05/22/84)
() In a recent discussion with a highly regarded photographer, I happened to ask him about the incredible sharpness of his phtographs. As a bit of background info - 3x4 foot murals of his still had the clarity and detail of an 11x14 inch print. But to get back on track, this photographer told me that other than having very close temperature tolerances during development, he felt that the mirrors in today's SLR's caused enough vibration at shutter speeds less than 1/250 to cause blurriness. He uses a Leica rangefinder. Does anyone have any other ideas about getting really, and I mean really, sharp negatives (35mm)? Or any other discussion? Simon Kao ITT Advanced Technology Center ...decvax!ittvax!wxlvax!smk
rwp@hogpc.UUCP (R.PAUL) (05/23/84)
[]
The hints I will mention on getting sharp negatives will probably
be obvious to the more experienced photographers in this forum, but
they may be helpful to some.
To begin with, the mechanisms for getting sharp negatives depend, to
a great extent, on the type of photographs you are trying to take. There
are different things that can and must be done to get sharp negatives of
scenic views, insects, action shots, and portraits. I will try to note
with the techniques I mention the types of photography to which they can
be applied.
Techniques:
1) Lense choice - whenever possible use the camera's normal lense (about
50mm). The maximum aperture of such a lense should be approximately f2
for maximum lense sharpness. This is good for static subjects at a com-
fortable distance in good light (e.g. daylight). However, if the subject
is small or very flat (e.g. writing on a piece of paper) a macro lense
(again about 50mm) would work better. Macro lenses are generally optimized
for flat field sharpness. The maximum aperture will probably be significantly
smaller (about f4.5). For sharp photos in low light, a fast lense is
recommended. For a normal lense, the aperture might be anywhere from f1.2
to f1.8. For a 135mm telephoto lense the range might be f2 to f3.5. For
action shots that really require a zoom (e.g. sports), the range might be
f2.8 to f3.8. Zooms are not recommended for getting sharp shots. However,
in some situations, they may be required.
2) Shooting aperture choice - when possible, shooting aperture should be
approximately the midpoint of the aperture range of the lense being used.
Wider apertures suffer from lack of field depth and smaller apertures
suffer from chromatic aberation. On a normal lense, this would be about
f16. This, of course cannot be applied to low light photography. It
usually does not apply to action photography in any light.
3) Use a tripod and cable release - this can only be applied to relatively
static subjects (I include portraits in this category). No matter how
steady your hands are, they shake more than a sturdy tripod. Camera shake
is probably the second most common cause of sharpness loss (the most common
is probably the use of a too slow shutter speed).
4) If a tripod is not available or not practical, brace yourself and your
camera - use a wall, a sturdy chair, a tree -- anything that will help you
gain stability -- to make your body more stable. If nothing is available,
at least make sure you have a firm stance (one foot slightly in front of
the other ...) and a firm, but comfortable, grip on your camera.
5) Shutter speed choice - if your subject is not completely static (this
may even apply to scenic photography on a windy day), choose a shutter
speed fast enough to freeze your subject. If you are hand-holding your
camera, remember the rule of thumb for slowest shutter speed selection:
no slower than the reciprocal of the lense length in millimeters (e.g
with a 135mm lense, the shutter speed should be 1/135sec or faster).
There is a definite tradeoff with technique #2 here.
6) If possible, immobilize your subject - this applies best to photo-
macrography. For instance, if you are photographing a flower outside
and at close range, try cutting off the wind around it by placing some
kind of barriers at strategic places. If the barriers are smartly
chosen the photo may even be enhanced by doing something like adding
fill light or diffusing the light source. Of course, it is also possible
to ruin the photo by choosing the wrong barriers. With insect photography
it may be possible to chill it, thus numbing it temporarily, and slowing
its motion.
7) If your camera has a mirror that can be locked up, use it - this works
only with static subjects and very few cameras have this feature, but if
yours does and the subject is right, this will prevent camera shake due
to mirror vibration. Of course a tripod and cable release are also necessary
to make this technique have any positive effect.
8) Use a fine grain film - this only applies in the best of light, but helps
immensely when it can be used.
9) Use a fast film - this conflicts with #8, but in low light it will allow
getting the best shutter speed/aperture combination for the photo being
taken. Perhaps #8 and #9 should be combined into one technique saying,
"Use the finest grained film lighting conditions will allow." Or maybe both
of them should be combined with #2 and #5 to say, "Optimize your choice of
film speed, aperture, and shutter speed."
I hope this list of techniques has been helpful.
Rick Paul
AT&T Information Systems Laboratories
Lincroft, New Jersey
{ihnp4,decvax,allegra}!hogpc!rwpgary@ixhte.UUCP (Gary Heermann) (05/23/84)
Leica lenses are made from select glass. If you dis-assemble a leitz lens you will find each element marked with a glass batch number. Glass from various parts of the world have different characteristics. A leica rep once told me that Leica combines different glass into the various elements of a lens to produce a particular contrast ratio. I believe this means that most of the light goes directly to the film without reflections, etc. within the lens. I can pick out negatives shot with a Leica from a stack of negatives lying on a table. The Leica negatives are so crisp they look like they were shot on different film. I remember going to a photo exibition and seeing a large (30x40 or so) print way across the room. I just knew it had to be shot with a Leica. It was an exibit for Agfa paper and the label on the print said it was shot with a Leica. There was a contact print attached just to prove it was from a 35mm. As for mirror vibration, the same Leica rep told me that they didn't produce a single lense reflex because they couldn't get the same sharpness. When they introduced their first SLR some years later, I remember I was very disappointed because I figured they were compromising themselves just to make a buck. I own two Nikons (both rangefinder), they are good but no comparison to the Leicas I have used. Gary Heermann AT&T Bell Labs
rsg@cbscc.UUCP (Bob Garmise) (05/23/84)
There is an article in this month's Modern Photography (June?) that implies that each lens has an optimal sharpness f-stop. For instance, if the lens ranged from f1.8 to f16, the optimal f-stop would be 2/3rds of the way to f16, or about f5.6(?). Other things that affect sharpness: - Another article compared 35mm with large format film. Obviously, the large format was sharper (for the price it better be!). - A tripod \ - Mirror lockup |- these are pretty obvious though - Subject lighting / ...bob garmise...at&t bell labs, columbus...
rcl@tellab1.UUCP (Ron Lewen) (05/24/84)
One thing most people tend to neglect when the attempt to achieve maximum sharpness is the processing. All of the suggestions I have read so far have been good ones, and they should be followed (to what extent is up to you), but after all this is done, you can wipe a lot of it out in the darkroom (I am mainly talking about B/W. I am not as familiar with color processing). 1. Film Developer The first contributor to mushy prints is the film developer. I learned long ago to stay away from "fine grain developers" like Kodak's Microdol-X. These developers contain a solvent that "eats" the edge of the silver-halide crystals in the film. This, as intended, reduces the visibility of the grain in the final print, but think about what it can do to sharpness! An easy experiment can be performed by shooting a roll of 12 exposure film (use your usual) of the same, or similar, scenes. Take this roll, and develop half of it in Microdol-X (or any other "fine-grain developer", and develop the other half in a "normal" developer (HC-110 is one, if my memory still works). Then print these negs at the same exposure, aperture, enlarger head height, etc., develop them at the same temperature and time, and then compare the grain. Use at least an 8X10 print, and a decent magnifier. 2. Processing time, temp, handling, etc. Another key to sharp negatives is how they are handled during processing. Processing time should be monitored accurately, and an effort should be made to keep a log of the best processing time for rolls shot outdoors on sunny days, outdoors on cloudy days, indoors under existing light, indoors with flash and so on. Keeping a roll of film in the developer too long will not only produce an overdeveloped neg, but will reduce sharpness due to the "eating effect" (this will happen with normal developers, but to a much lesser extent than with "fine grain developers". Processing temperature can have a big effect on sharpness, and not only absolute temp, but relative temp. Absolute temp effects sharpness in that the film will be in the developer longer at lower processing temps. Sharpness will not be lost here because of the "eating effect", but simply because the film will have a chance to soak up more moisture (and chemicals), and will experience more shrinkage and curling during drying. Wet time for the film should be as short as possible (without sacrificing "archival" quality, i.e., the ideal of total removal of chemical residue from the negs, but that is another discussion). Since I mentioned shrinkage, lets talk about relative temperatures and their effects on sharpness. Consider a roll of film developed at 75 F for 7 minutes. At the end of this 7 minutes, the film has pretty much reach an equilibrium with the water, and is close to 75 F. Now lets dump out the developer and pour in a stop bath (or water if you chose) at 82 F. This sudden change in temperature is going to cause the surface of the film to expand slightly. Since the warmer stop doesn't reach every spot on the roll at the same time, the surface of the film reacts differently at various location. Now lets throw in a fixer at 77 F, throw it into a water bath at 68 F and dry it at 72 F. That poor film is expanding and contracting so many times, and in so many directions, it's a wonder it can get back close to normal! Well, maybe I exaggerate a little. But seriously, the film does expand and contract with temperature changes, and when drying, and these motions, however small, can distort the image. This distortion may not be noticeable without a microscope, but when you want to make mural size prints, even the slightest aberration can show up. 3. The printing process This could be the weakest link in the whole darkroom. How many amateur photogs bother to use a grain focuser when printing? If you do, do you place an old sheet of paper of the same type you will be printing on under the focuser? Think about it. It makes sense that if you are going to go through all the other steps listed above, and in other articles, you may as well take the time to focus the enlarger as accurately as possible. This is where the old piece of paper comes in. With the grain focuser, you are actually focusing on the grain in the film. If you set the focuser on the easel directly, you will have focused the enlarger for a spot a full paper thickness below the actual printing surface (the surface of the paper). With the focuser on a piece of the same paper, you are focusing on the printing surface, and will achieve greater sharpness. What about the enlarger itself? Keeping the lens clean will help, as will cleaning the condensers (if your enlarger has them). Also clean the neg carrier if it has glass. Speaking of neg carriers, make sure that the neg is flat! Nothing is worse than to spend the time required to make a print only to realize that the spot you used to focus on was the lowest spot on the neg! (on this note, check the focus at several points to be safe.) In addition, let the neg warm up before you focus! If you focus with a cold (or cool) neg, and it buckles as it warms up, the print will be out of focus! 4. The enlarging lens When you buy a new lens for your camera, do you buy the cheapest lens available, thinking that a lens is a lens, and no one will ever know the difference? Probably not. So why do the same for your enlarger? There are some excellent quality enlarging lenses on the market, and they really aren't that expensive (you can, however, spend several hundred dollars if you really try!). Buy a good lens! Again, if you are really serious about sharpness, the enlarging lens is as important as the camera lens, and maybe even more so. For 35mm negs, I use a 50mm Nikkor-E (I think... My memory is slipping as of late), and for 4X5 negs, I use a 150mm (again, I think) Rodenstock Rodagon (or something close to that). I really like the Rodenstock. It even has a little lightpipe that lights up the aperture dial so you can see what you are doing (the lightpipe is safelight orange, of course). The same comment made about the aperture of your camera lens holds for enlarger lenses; use an aperture setting about midrange for the lens. And...As mentioned above, KEEP IT CLEAN! Dust is one thing, but never get finger prints on any lens. Human skin oils have a nasty habit of eating into the coatings on photographic lenses, and a neglected finger print can ruin a lens. Well, I have rambled on long enough. I hope that I have said at least one thing that will help. Comments? Questions? Mail them to me. Flames? Mail them to /dev/null, my fragile ego can't handle them! By the way, if you have a couple of scenes that you would like mural size prints of, and are really interested in sharpness, try renting a 4X5 (or larger) view camera. You will probably have to enlist the help of a friend with a good back to help carry the equipment, but the results are worth it. I have a couple of 40X50 inch murals I printed (in my own darkroom, but that, too is another article) that came out just beautiful (pat pat pat... I hope I don't hurt my shoulder reaching around to my back like this). If you don't know how to use a view camera, there is bound to be someone in the local camera shops or clubs that will be willing to help. If not, any school that has a decent photo department should have classes (and the school may have equipment you can use!). -- Ron Lewen ....ihnp4!tellab1!rcl <---------------------------------------------------------------->
marcus@pyuxt.UUCP (M. G. Hand) (05/25/84)
<one fo you and the rest for me...> Every manufacturer uses a variety of different glasses in the construction of each lens - the different refractive indices help to control the various aberrations of the lens design. The control of internal reflections is a secondary consideration and anyway have most impact on contrast. Some of the Canon lenses, incidentally, - mostly the longer ones - use quartz elements which transmit blue light better. Some of the cheap lenses have noticeable colour fringing - a rainbow effect around the edges of objects caused by the glass transmitting light of different wavelengths at different speeds, more commonly recognised as the dependence of refractive index on wavelength. Another important factor in image sharpness that i don't think has yet been mentioned is the physical alignnment of elements inside the lens. This becomes more difficult as the focal length of the lens shortens (actually it is more *critical*) - hence the high price of good super-wide angle lenses. Allignment at longer focal lengths is less critical - transmission (lens speed) is ususally more important. There is also some confusion between resolution and contrast - a high contrast low resolution lens often appears to give better sharpness than a lower contrast high resolution lens. Finally, the design of any lens is to some degree a compromise between these factors, others which have been mentioned in other follow-up arguments, and cost. Obviously the price you pay will reflect the care with which the lens has been designed and assembled. I would expect Leica lenses to be close to perfect by this criterion! This is also illustrated by Canon again - they market 4 (yes four) different 300mm lenses which vary speed, quality, glass (or quartz) used and, of course, price. marcus hand (pyuxt!marcus)