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Pentax Takumar 300mm f/4 lens

gfletcher

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Psychobilly

Psychobilly

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Thinner is better at least when it comes to achieving infinity focus... what you might find is that infinity focus is achieved slightly before you reach the infinity mark on the lens...

I modified one of them to give me a low profile focus confirm EOS-T adaptor for soemthing I was playing about with last year...

Billy...

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gfletcher

gfletcher

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I have discovered that if you remove the end cap which has the M42 thread on ( 3 slot head screws) , there are 3 shims within this end cap that can be removed.

The total thickness of these shims combined seems to be maybe 1.5mm.

I believe that this should allow infinity focussing using the M42 to EOS adaptor.

I will check it out tonight if it stays clear.

Graham

shim1.jpg

shim2.jpg

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gfletcher

gfletcher

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I am pretty certain that this lens on my Canon 1000D unmodded camera will now focus at infinity .

The setting on the camera lens is a small amount from the infinity symbol on the lens :)

As to whether it will focus at infinity on my 350D modded is not certain at this stage.

I will know better if i can try to get an image of the moon this evening.

I assume that these shims are put there to allow the user some inward focus tolerance when used with a (non M42 Camera).

Just a lucky find i guess :D

Graham

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Bizibilder

Bizibilder

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Just had my own lens apart - I have 0.9mm of shim. This may be enough but I think I will turn down the end of the "cup" shaped end piece as it seems to foul the tripod mount "thingy" and wont allow the cap to go further on. I'll let you know how I get on once I've cut metal.

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gfletcher

gfletcher

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A quick image taken with the 1000D and lens.

This was not at the infinity setting , there is still extra inward focus on the lens than this picture depicts :)

moon2.jpg

You can definitely make out crater detail around some parts of the limb/I understand this is not the best time to image but i think it shows that the shim removal has done the trick.

Graham

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