 Luie Toscano |
How to get sharp pictures on a Pentax 67II I am fairly new to photography. I started with a DSLR which I feel was a good learning tool. Now I have decided to step up to a medium format camera to shoot landscape photography and have purchased a Pentax 67II with AE prism. My question is what is the best way to get sharp images. If anyone has experience with this camera, what lens (45mm, 50mm, 100mm, 300mm) and at what apertures give the best results. I have read enough on this camera to realize a heavy tripod is necessary, the lack of a fast flash sync speed a bit of a problem, and I need to use the MLU. I have also read attaching a bungie cord to the tripod and looping it to your foot and stepping on it will help. A bean bag on the prism. Any info on any of this or anything I am missing would be helpful.
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Alan N. Marcus |
Hi Luie, While I never owned a 6x7 SLR, I always wanted one. So, in a way I envy you. The 6x7 format actually measures (image area) 56mm x 69.5mm with a diagonal measure of 89.25mm. That being the case, a lens 80 ~ 100mm is considered normal (we choose normal based on the diagonal. This is true because such a lash-up about duplicates the human experience as to prospective and more importantly, it takes a lens in that range to give even coverage without resorting to extraordinary means in the design of the glass. By coverage, I am talking about the fact that lenses vignette. All lenses output a circular field. The 6x7 image area occupies just the central portion of the image projected by the lens. The periphery of the projected image is masked off. Even so, less light energy reaches the margin of the projected image. This is called cosign error. Imagine you are a tiny being walking about on the negative, looking back at the lens during the exposure. At the middle of the image area you look up and see a near perfect circle of light, that the boundaries of the iris. At the edges, you look up and see an ellipse. The iris as an ellipse has less surface area thus less some light energy is absent at the image’s perimeter. In other words, expect some vignette from the shorter lens. As to sharpness, all lenses are not created equal. Even two identical lenses, produced on the line at the same time, will likely not be an exact match. Except for the quality of the inspection, you are at the mercy of the gods. That being said, longer lenses are easier to make as they required less power meaning the curves are gentle. Most every lens performs better stopped down. This masks off the perimeter of the lens where the curve is steepest. Stop down too far and diffraction begins to set in. This is caused by light rays being deflected as they brush by the blades of the iris. As you stop down a higher percentage of such glancing blows exist. Generally the sharpest setting will be 2 ~ 2 ½ stops stopped down from maximum opening. The old masters got away with f/64 and f/32 because they were using 8x10 view cameras requiring a 325mm is normal thus at f/64 the aperture diameter is 5mm, still large enough to avoid diffraction.
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Luie Toscano |
Thanks for the info Alan
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John G. Clifford Jr |
There are some great bargains in medium-format film cameras now that everyone's moving to digital. If I wanted to take sharp photos, I'd want good light (or a flash/strobes), a heavy-duty tripod, and I'd want to stop my lens down between f/8 and f/16. Because the diagonal measurement of a 6x7 negative as about twice as big as a 35mm negative, the field of view of a particular lens is about twice that of the same focal length in 35mm. In short, a 100mm lens is 'normal' for the 6x7 format and the field of view is comparable to a 50mm lens on a 35mm camera (or full-frame digital SLR). Pentax made some excellent lenses for this camera. Because I like shooting mostly landscapes, I'd get the 50mm and 100mm lenses. You should be very pleased with the results given a good tripod, a reasonably fast shutter speed, and stopping the lens down a couple of stops.
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John H. Siskin |
Hi Luie, I have used this camera, but rarely. I owned Mamiyas. It is a quality product, and, to the best of my knowledge all the lenses were good. I would consider using the self-timer, if there is one in addition to the mirror lock up, if you are shooting a long shutter speed. I would avoid long shutter speeds and look for particularly sharp film, such as Velvia and T-Max 100. If you plan on making any prints using a computer invest in a really good scanner, or get drum scans made. Poor scans give poor results. Thanks, John
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Luie Toscano |
Thanks everyone for your help
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