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05-11-2016, 06:55 PM   #1
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Dangerous ideas. Can the 60-250 be changed to FF?

Inside the 60-250 is a felt covered ring. I'm wondering if removal of the ring would result in usable quality at telephoto range.

I think this ring may be blocking the light because the lens vignettes at the telephoto end.

Anyone going to brave the change?

05-11-2016, 06:59 PM   #2
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There was a thread where a person did that on here a few months ago and said it worked.
05-11-2016, 07:13 PM   #3
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QuoteOriginally posted by VoiceOfReason Quote
There was a thread where a person did that on here a few months ago and said it worked.
Are you going to do it to yours?
05-11-2016, 07:14 PM   #4
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Isn't it good enough without? Just don't go all the way to 250mm- it's not that much different than the 200mm setting, after all.


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05-11-2016, 07:17 PM   #5
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Found the link: https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/304092-da-60-250-mod-ff.html
05-11-2016, 07:35 PM - 1 Like   #6
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QuoteOriginally posted by Clinton Quote
Are you going to do it to yours?
If it ain't broke...
05-11-2016, 08:59 PM   #7
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I would be tempted if I owned one and a K-1. From what I remember of the previously mentioned thread is that it's reversible. Much less scary than shaving the hood petals off of a DA 10-17 fisheye which is another lens mod I've seen done to widen its effective range for FF.
05-11-2016, 10:19 PM   #8
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Interesting thanks for posting this.

05-12-2016, 12:56 AM   #9
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Really interesting, thanks
05-12-2016, 04:11 AM   #10
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I'm not an qualified optician, but I have a lot of experience making all kind of experiments with refractor telescopes and eyepieces. This kind of fix diaphragms has an important role. If you take one out, maybe you will get a wider image circle, maybe not. But certainly, will have a fuzzier image.

For comparison, remember that almost any lens is sharper not at it's bigger opening, but when you close it about two stops.

So, If this ring is after the last element of the lens, you can try, but don't expect for the same image quality. If this ring is inside, between elements, forget it.
05-12-2016, 04:36 AM   #11
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I'm not tempted to try it on mine. My initial tests with my new K-1 and the 60-250mm gave me acceptable results, even with the 1.4 HD converter. I can live with the small amount of dark corners.
05-12-2016, 06:46 AM   #12
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I think the * 60-250mm is a FF design, according to its patent. But it has that back baffle. There were threads about removing it, but I have not seen any sample photos with before/after, so that we could tell what exactly happened. Maybe now that K-1 is out more people would have incentive to try this. Maybe someone can even offer this mod as a service, maybe even Pentax themselves. It certainly seems like a good lens, and if a small modification can make it perform better on K-1, why not. Its a "at your own risk" type of thing, though

QuoteOriginally posted by JimmyDranox Quote
For comparison, remember that almost any lens is sharper not at it's bigger opening, but when you close it about two stops.
You're saying that ring acts as an aperture? Its possible, but only for wide open. Wouldn't the aperture blades be the actual aperture on all f-stops except wide open?
So yeah, this might affect performance wide open, increasing image circle diameter, possibly increasing aperture (very interesting idea), and softening the image. I think the main issue would be lower contrast, as less light might get absorbed by the felt, so it could continue to bounce around the mirror box.
05-12-2016, 09:18 AM   #13
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Take a look at what people did in China.You might need google's help, but the pictures are easy to understand
625
05-12-2016, 09:19 AM - 2 Likes   #14
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QuoteOriginally posted by VoiceOfReason Quote
If it ain't broke...
As a humble carpenter and all-around handy man (that was in all honesty blessed with the ability to work with any material and turn it into a work of art and/or simply invent something astoundingly ingenious), my grandfather loved saying

"If it ain't broke, I can fix it!"


In fact that was what his tagline was on all his business cards.

-Heie
05-12-2016, 09:31 AM - 1 Like   #15
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If it is a light baffle you could get more internal reflections leading to loss of contrast, ghosting or whatever. Maybe correctable in PP. A nice round of before and after shots are in order.
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