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12-22-2010, 07:10 PM   #16
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QuoteOriginally posted by dadipentak Quote
Then I must be misinterpreting my experience. I achieved sharpest focus somewhat short of the max focus distance and also found I couldn't get everything in focus at the same time.
Right, as was just posted, the limit of focus is not necessarily the infinity focus point. I don't have a particular explanation for not being able to get the whole thing in focus at the same time.

Just for fun, I ran some numbers through a DOF calculator. With the moon at 400000 km away, using a 600mm f/2.8 (!) lens, focused on the moon, the sharp region of the image should be between 6 km and infinity. As the moon is only 3500 km in diameter, it comfortably fits in this range

12-22-2010, 07:50 PM   #17
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QuoteOriginally posted by sewebster Quote
. As the moon is only 3500 km in diameter, it comfortably fits in this range
That's reassuring.
02-11-2017, 06:38 AM   #18
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I had the same perceived focus issues years ago, when I got my copy oth the 500/4.5. I readjusted the focus, but it is a tedious task. After that, the images were not sharper at all.
I made comparisson shots with other 500mm lenses (Meyer Optics 500/5.6, Tokina 500/8 mirror) and in real world shooting, they all delivered comparable results. The sharpness of shots over long distances is compromised by atmospheric limitations (what astronomers call "seeing"). THat is part of the problem, which cannot be resolved. At short distances, this effect is neglible.
Also, we shouldn't forget, that the lens design is very old and resolution and constrast modulation may simply not up to the task to be really useful for modern high-res DSLRs.
And lastley, there is the problem, to avoid camera shake or motion blur, which such a long and heavy lens. You will need a VERY sturdy tripod and head combo, to steady this lens - and still very short exposure time are preferable.

By the way: with very short exposure time you can also improve the sharpness of moon shoits, as you may "freeze" a moment of good seeing and reduce blur, this way.
Ben

P.S.: I know, this thread is old, but the issue pops up now and again...
02-11-2017, 08:10 AM   #19
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Ive had a similar issue in the recent past. I sent a couple lenses to Erik and had them adjusted to focus slightly past infinity.
Using Live View , Focus Peaking , and a very Large monitor on a 25" cable still gave me mediocre at best Moon shots.
I have found its better for me to have a lens infinity stop set to just past , or at the very least spot on.
There is nothing worse than a nice lens to have the OO stop set just a hair too short as You will never get a sharp focus.
Just my two cents even though I finally gave up on old Tele Takumar lenses for moon shots.
It seemed that I had to stop way down also for anything even half way acceptable.

02-11-2017, 02:45 PM   #20
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Gerjan says the S-M-C 1:4.5/500 focus just past infinity.

I did adjust mine, however not using any screwdrivers. I did have to try many helical threading combinations to get part of the inner rear element group to gain 1mm more movement range. The two helicals need to be threaded onto correct positions from their maximum range of motion to allow full range of focus adjustment to include infinity & a little beyond -- that must seem like gibberish unless you have done it.

The improvement in infinity photo quality is easy to see; compares with quality closer.

Tip: Photograph a distant laser point to see how still is the camera mounting system.

For some fun mount the laser on the camera & walk over to the laser point to watch it move as an assistant simply walks the ground near the tripod!
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