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03-13-2016, 10:40 PM   #1
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How to clean a F 50 1.7 ?

Hey everyone, didn’t know if I should post here or in 'Repairs and Warranty Service'...

I bought a cheaper, ‘well used’ F 50 1.7 the other day and it seems to take excellent pictures. However, there are some minor issues that I should maybe take care of before they interfere with the excellent picture taking.

1) The blades seem excellent except for that single scuff on the rear blades. The blades are clean and snappy, though. I don't think it's affecting the photo quality, but is this something to be fixed? Would it be an easier clean?

2) A small hair is jammed (not moving) in the distance scale closure and it's pretty dusty too. Besides being unsightly it doesn't seem to affect the performance, but is this something I need to get fixed? Would it be an easier clean?

3) Also, anyone have a tip on how to take pictures of aperture blades without getting so much glare while still illuminating the blades?


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03-14-2016, 05:51 AM - 1 Like   #2
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Before thinking of doing it yourself, it's probably better to bring the lens to a repair shop and ask for an evaluation. A simple cleaning without replacing any parts should not be too costly and not worth the risk of breaking the lens.
03-14-2016, 06:12 AM - 1 Like   #3
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Its looking very nice to me. I would myself let it be the way it is. If you don't have skills of disassembling lenses and dealing with optic blocks, and dust-free area to make it, I strongly recommend to just be happy with it. It should not affect you photos at all
03-14-2016, 07:17 AM - 1 Like   #4
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3). Have you tried using a polarising filter?

03-14-2016, 08:08 AM - 1 Like   #5
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If everything is working I would not touch it. It looks clean to me!
03-14-2016, 08:52 AM - 1 Like   #6
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Personally, I would not risk taking the lens apart for such minor faults.
03-14-2016, 09:34 AM - 1 Like   #7
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You can check the aperture blades by using a tripod and pointing at a target with constant lighting. Use Av mode, fixed ISO at something low, and the 2 second delay. Take a shot at f5.6 to check exposure and adjust compensation if there is under- or overexposure. Then use the AE-L button to lock that exposure. An asterisk will show up on the display when it's locked. Now you can turn the e-dial to any aperture and the shutter speed will follow along. Take shots at a range of apertures. Quicker to do it than write it. Bad aperture blade movement will slow down at small apertures like f11, f16, f22, so those shots will be overexposed. A consistent fall-off, more than a stop, is a problem. (You'll see some normal differences in the histogram between wide open, f8 and f22, reflecting the natural lens characteristics and depth of field.) Don't worry about it otherwise.

The lens is not that difficult to take apart but I agree it's not necessary. I'd definitely want some JIS screwdrivers before I started. I'm not sure if there are any instructions for the mount side. I have some photos to start on the front end. An autofocus lens probably has a contact fork (this one does) that can be easily bent if you don't find it and remove it first. Don't lose any other tiny electric parts.
03-15-2016, 07:22 AM - 1 Like   #8
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The chip on the blade is likely to have zero effect on the images. If it really bothers you, the entire rear group unscrews by turning it counterclockwise, and you can simply touch the blade up up with a fine-tip sharpie or a very tiny bit of gun blacking. Don't use paint or anything else that will add appreciable thickness to the blades, since that can interfere with the opening and closing action.

The hair can be gotten one of three ways. The focus ring is a plastic piece that is glued on, and if you are VERY careful, you might be able to pry it loose without cracking it and then blow the hair out with a bulb-style blower. Secondly, the window to the focus scale is held down by double-sided adhesive tape and also can very carefully be peeled back (it is rigid and can also crack). I recommend using a nylon spudger stick or similar for prying since a metal screwdriver or the like is apt to scar the plastic. Be aware that it is often difficult to get it to stick back as well as it did originally once the original tape seal is broken. The last way involves removing the whole focus assembly, which I would NOT recommend for a beginner, since there are some very fragile contacts you would be working with. This method would also require JIS drivers, which the other two wouldn't.

Note that these are tips only for the very OCD photographer, and if the lens is shooting fine currently are completely unnecessary, as others have stated above

03-15-2016, 11:35 AM - 1 Like   #9
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QuoteOriginally posted by FozzFoster Quote
I bought a cheaper, ‘well used’ F 50 1.7 the other day and it seems to take excellent pictures. However, there are some minor issues that I should maybe take care of before they interfere with the excellent picture taking.
You do realize that lens was in production from 1987 to 1991, right? So it is at least 25 years old. Any item will gather all kinds of damage and gunk in that time. Even in just a couple years. My opinion? The lens is fine, leave it alone. Use a rocket blower to clean the outside, leave the inside all alone until you see optical problems.

OR - "that terrible, terrible damage is totally unacceptable, the lens has zero value, you should immediately send it to me and forget about it."

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