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Forum: Troubleshooting and Beginner Help
04-14-2011, 01:22 PM
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I think I was agreeing with you. :)
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Forum: Troubleshooting and Beginner Help
04-14-2011, 11:50 AM
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All of the Pentax 50mm f1.7s have the same optical formula, and produce nearly identical results. There are slight differences in lens coatings in different series, so colors are slightly different too. It doesn't matter in practice. My comments on each series:
M - A few of these were made in Taiwan, and won't say JAPAN on the front. The ring with the lens name might also be stamped plastic instead of engraved aluminum. No internal differeence that I can see.
A - A pretty good value purchase. You have to enter the focal length for SR, and focus, but it works well with other features, especially flash. Make sure the A setting works or you can return it if it doesn't. I wrote an article on fixing it but best not to have to. Once the A setting works, it doesn't need to change. More plastic here.
F - Fully compatible and autofocus, this is a good choice if manual focus is not an option. The biggest drawback to this lens is manual focus. The thin ring and limited arc of travel make it trickier than the manual focus versions. Plastic over metal. Sometimes the plastic filter ring chips or cracks. These lenses sell for less. Buy one, find an old metal 49mm filter, remove the glass, and install it permanently.
FA - This series has a little more damping in manual focus and a wider ring. Cosmetics are different and the lens can tell the camera where it is the sharpest. The lens is rarer and sometimes sells for a big premium. I don't think it's worth it. The extra information is only used for certain Program lines. Since the 50/1.7 is pretty sharp everywhere, it's not that important a difference.
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Forum: Troubleshooting and Beginner Help
04-13-2011, 03:58 PM
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You can do some practicing now with your current lenses - 50mm is going to give you the same image size on either one. The traditional portrait lenses for 35mm film were from 85mm to 135mm, which kind of means 55mm to 90mm on your camera. [From now on, forget about film.] The range was chosen because it flatters facial features and fits the traditional framing of studio shots. That doesn't mean you are stuck with using only that range. Below 35mm or so, you might notice more prominent noses from the fromt or ears from the side. Above 100mm and you can't communicate that well with the subject. Experiment a little in your home with setups you might use.
Another thing you can test is light available in potential portrait locations, like by a window or in a certain chair. Even if the test photo is not usable, you can see if it would have been better with a lens that lets in more light. Say you can take a reasonable exposure at 50mm, 1/100 sec., f5.6, and ISO 3200, but the noise is annoying. If you had the Pentax-M 50mm f1.7, you could use f2 and ISO 400 instead.
Without the actual lens, you can't see the effects of depth of field or practice focusing. Those may be issues with the fast prime lenses. You can use an online depth of field calculator and estimate distances. It's possible to get just one eye in focus and have the nose be soft (not a good look). At larger distances or wider focal lengths, it's less of a problem. In a darker room, focusing can be tricky. Portraits tend to look better when the eyes are exactly in focus and the face is within the depth of field. If the foreground and background are outside that area, the viewer sees the face in 3D and responds positively. Executing this well needs some practice but is worth the effort.
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