[séamuis]

Newarts poted an image of his 50mm macro that *looks* like it has a filter at the base of the lens and said that it has a 49mm filter. Maybe I have misinterpreted his sentence, though.

no that's not a filter that's just the base of the lens. how would you mount a filter to the back of the lens?

[newarts]

Originally Posted by Andi Lo View Post

Newarts poted an image of his 50mm macro that *looks* like it has a filter at the base of the lens and said that it has a 49mm filter. Maybe I have misinterpreted his sentence, though.

no that's not a filter that's just the base of the lens. ....

I'm sorry I didn't make that clearer. Earlier there had been reference made to some small Takumar lenses requiring a 49mm filter which in turn implied they'd have a small base.

[Andi Lo]

no that's not a filter that's just the base of the lens. how would you mount a filter to the back of the lens?

Ah, I see. I thought that might be the case. Thanks for clarifying Although I actually think attaching a filter to the back of a screwmount lens should actually be possible with a 42mm filter if it's double sided. One sice screwed to the body (or adapter), and the other end to the body of the lens. It *should* work since both are 42mm in diameter. No idea if something I'm unaware of might prevent it from doing so, though.

*edit*: I just checked the back of my 50mm and it seems that if I attach a filter at the back, the filter would get scratched from the pin. Might be worth a try if it can work as an extension tube though. I'm just a newbie though so feel free to correct me.

[wallyb]

Ah, I see. I thought that might be the case. Thanks for clarifying Although I actually think attaching a filter to the back of a screwmount lens should actually be possible with a 42mm filter if it's double sided. One sice screwed to the body (or adapter), and the other end to the body of the lens. It *should* work since both are 42mm in diameter. No idea if something I'm unaware of might prevent it from doing so, though.

*edit*: I just checked the back of my 50mm and it seems that if I attach a filter at the back, the filter would get scratched from the pin. Might be worth a try if it can work as an extension tube though. I'm just a newbie though so feel free to correct me.

I believe you mean a 42mm filter?

EDIT: And, well, yeah :P

[Mike Cash]

Ah, I see. I thought that might be the case. Thanks for clarifying Although I actually think attaching a filter to the back of a screwmount lens should actually be possible with a 42mm filter if it's double sided. One sice screwed to the body (or adapter), and the other end to the body of the lens. It *should* work since both are 42mm in diameter. No idea if something I'm unaware of might prevent it from doing so, though.

Try it and what you're almost certainly going to experience is failure to operate followed by abject horror when you remove the lens and find your mirror has been shattered-shattered (sh-dooby shattered).

[X Man]

... and find your mirror has been shattered-shattered (sh-dooby shattered).

LMAO, I needed that, thanks!

Sh-Dooby,
Mike

[georgweb]

Cash said:
Try it and what you're almost certainly going to experience is failure to operate..."

Mike,
why would that be so? I would reject the idea for other reasons, namely loosing infinity and also impossible on most lenses,
cause the inner group would wander through the filter glass on infinity position.

I am still looking for an M42 filter to put on the back of my bellows, in order to prevent huge amounts of air being pumped into the camera.
I doubt that there are filters really suitable for this so I'm considering just glueing some glass into the back of that bellows.

Greetings, Georg (the other)

[Mike Cash]

I thought he meant something going on the back of the lens with the lens still mounting flush to the camera body.

Someone correct me if I am wrong, but don't filter threads have a different pitch than mount threads?

[georgweb]

I see what you meant, Mike.

Filter size in (Pentax) M42x1.0 seems rare. T-mount is M42x0.75 BTW.

The rest is stolen from the wikipedia 'photographic filters' site:
"The most common standard filter sizes for circular filters include 30.5 mm, 37 mm, 40.5 mm, 43 mm, 46 mm, 49 mm, 52 mm, 55 mm, 58 mm, 62 mm, 67 mm, 72 mm, 77 mm, 82 mm, 86 mm, 95 mm, 112 mm and 127 mm. Other filter sizes within this range may be hard to find since the filter size may be non-standard or may be rarely used on camera lenses. The specified diameter of the filter in millimeters indicates the diameter of the male threads on the filter housing. The thread pitch is 0.5 mm, 0.75 mm or 1.0 mm, depending on the ring size. A few sizes (e.g. 30.5 mm) come in more than one pitch."