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11-22-2010, 12:11 PM   #1
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Any point in higher f-stop modification?

I was looking at my 58mm 1:1.5 rokkor lens and noticed that it would be fairly simple to mod it to be able to do higher than f/16.

I could probably add one or two more stops. The smallest it would physically be able to close leaves about the same size hole as a pin would leave when pocked through a piece of paper.

Would there be any point at all in doing this?

11-22-2010, 12:31 PM   #2
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QuoteOriginally posted by cyclone3d Quote
The smallest it would physically be able to close leaves about the same size hole as a pin would leave when pocked through a piece of paper.
I imagine that diffraction would be pretty severe at this aperture setting, leaving you with a rather blurry picture. You might like the effect, but at the same time, you *could* do some damage and ruin the lens' usefulness at the most commonly used apertures.

Just a thought. How often do you shoot over f16? Keep in mind that most lenses are their sharpest at f 8 - f 11, and that past f16, things tend to get fairly soft (although you might like the effect).

Just a thought though... you could use your kit lens or similar at f32-f40 and likely not see much difference in quality between that and your nice 58mm prime closed down that small...
11-22-2010, 12:56 PM   #3
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QuoteOriginally posted by paperbag846 Quote
I imagine that diffraction would be pretty severe at this aperture setting, leaving you with a rather blurry picture. You might like the effect, but at the same time, you *could* do some damage and ruin the lens' usefulness at the most commonly used apertures.

Just a thought. How often do you shoot over f16? Keep in mind that most lenses are their sharpest at f 8 - f 11, and that past f16, things tend to get fairly soft (although you might like the effect).

Just a thought though... you could use your kit lens or similar at f32-f40 and likely not see much difference in quality between that and your nice 58mm prime closed down that small...
I very much doubt it would damage the aperature as the aperature linkage is what stops it from closing any more.

I thought it might be a decent way to have a lens that could give me the option to get pinhole camera type photos.
11-22-2010, 01:18 PM   #4
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If you're interested in pinhole photography, it would probably be best to get a laser drilled pinhole. Diffraction gets worse with imperfections in the pinhole. I'm guessing that the old Minolta lens has straight aperture blades and so it won't be even close to round. Because of that, diffraction will be far more pronounced than on a true pinhole.

11-22-2010, 01:44 PM   #5
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Also I believe the pinhole look is partially due to the lack of optical elements. It's a very cool look, but I don't think you will get it from a lens.

Buy an extra body cap, heat up a pin, and poke a hole in the middle. On the back, glue or tape on a thin sheet of glass or plastic (the type used for cokin filters). That would likely work for the vintage pinhole look. For extra vintage points, use a yellow filter .
11-22-2010, 03:42 PM   #6
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QuoteOriginally posted by paperbag846 Quote
Also I believe the pinhole look is partially due to the lack of optical elements. It's a very cool look, but I don't think you will get it from a lens.

Buy an extra body cap, heat up a pin, and poke a hole in the middle. On the back, glue or tape on a thin sheet of glass or plastic (the type used for cokin filters). That would likely work for the vintage pinhole look. For extra vintage points, use a yellow filter .
This sounds like the kind of ridiculous thing I would try. Can you explain it a little more?

I have some Cokin type square filters that I'm never going to use, but why did you mention those in particular?
11-22-2010, 04:20 PM   #7
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QuoteOriginally posted by Ira Quote
This sounds like the kind of ridiculous thing I would try. Can you explain it a little more?

I have some Cokin type square filters that I'm never going to use, but why did you mention those in particular?
No reason other then I just figured that it would be good to cover the hole with something to prevent dust from entering the body, and those little plastic filters are meant for photography, so they *might* be clearer than the other sorts of clear plastic one might find around the house. I could be totally wrong there, but if I was going to try this (and I have those filters lying around) I would use them with the assumption that they would be more appropriate.

Heck, if you simply tape the plastic on you could try all sorts of things... saran wrap, plastic packaging for toys, that material used for 3d glasses...

As for a further explanation... well I'm not sure! If I was going to do it, it would likely be rather haphazard. I would want to buy a black cap to prevent light from getting through, and use a compass and ruler to mark the exact center. I got a black pentax cap with my program plus, so I know they are out there.

Next, I would take a very fine sewing needle, heat it up with a lighter, and quickly poke a hole (but I would NOT push it all the way through) in order to get the smallest hole possible. I would poke the hole from the side that sits inside the camera, so the material would be pushed out (allows you to cover the hole inside more easily). Next I would clean off the front of the cap of any little bits, and tape some material onto the hole. Take a picture, and see whether I like the size. If it is too dim, I would take off the material, heat up the needle, and try to open it a little wider. I made a film pinhole camera in highschool, and there was no "perfect" size. The camera (and "lens") was made out of cardboard!

If you want to get specific, look here: Pinhole camera - Wikipedia, the free encyclopedia

Finally, I would cover the hole with some sort of material (on the inside for aesthetic reasons). You could tape it in, so you have the convenience of swapping out different filters, or you could glue it in, and make another pinhole lens when you see fit! If I was to do it, I would use a light yellow filter, to get a nice warm image... or maybe sepia? I would probably try a few before I settled on one.

If you do try this, let me know how it works out! I'm starting to think it might be fun myself...
11-22-2010, 04:28 PM   #8
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I have plenty of black body caps:

One K-mount, and about six M42 (from my Spotmatics). And I don't see any reason that the M42 wouldn't work.

But will I actually be able to SEE through that tiny pinhole? Also, do I have to first max out the ISO to approach any kind of properly metered image?

11-22-2010, 04:40 PM   #9
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you will damage the aperture blades!

Modifying the rotation of the aperture ting to travel further, while simple and possible, will cause the mechanism to move further, and potentially beyond the range of motion, causing the blades to jam catch or bend. At this point the lens will be useless.
Unless you really know what you are doing I would NOT undertake this. As others have noted, there are easier ways to get reduced aperture effects, either with pinhole caps or ND filters
11-22-2010, 04:46 PM   #10
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QuoteOriginally posted by Ira Quote
I have plenty of black body caps:

One K-mount, and about six M42 (from my Spotmatics). And I don't see any reason that the M42 wouldn't work.

But will I actually be able to SEE through that tiny pinhole? Also, do I have to first max out the ISO to approach any kind of properly metered image?
I don't think you would be able to see anything through the viewfinder... I have no idea really - you might be shooting blind (on a tripod to boot). Pinhole exposures are in the 20 - 30 second range, in daylight.

Then again, maybe you will, but it will certainly be very very dim.

Since I was able to do this with film, I can't see why you would not be able to do with with ISO 800 or less. This sort of thing is for still scenes only... but hey, it's a cheap experiment.

Last edited by paperbag846; 11-22-2010 at 06:58 PM.
11-24-2010, 02:30 AM   #11
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QuoteOriginally posted by Lowell Goudge Quote
Modifying the rotation of the aperture ting to travel further, while simple and possible, will cause the mechanism to move further, and potentially beyond the range of motion, causing the blades to jam catch or bend. At this point the lens will be useless. Unless you really know what you are doing I would NOT undertake this. As others have noted, there are easier ways to get reduced aperture effects, either with pinhole caps or ND filters

+1 I agree, the risk of damaging a perfectly good lens just isn't worth it..get a circular polariser or ND filter they waste enough light to make longer exposures possible, plus polarisers can help get rid of reflections.
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