stupid filter threadsize question

[morgan]

So I'm taking a photo class and need filters for my new cv 35/2.5 cs (we're shooting infrared so i need the red filter). What size is that lens? 39? thanks...

 

[markinlondon]

I'll second Mango's answer on the filters.
Just out of idle curiosity, does that lens have an infrared focussing index?

Mark

 

[rxmd]

Mine doesn't. I guess it's trial and error, or stop down fo f/11 or so and hope.

Philipp

 

[jaapv]

It is an old trick to cut a 1 mm wide strip of mm paper and stick it to the focussing index to be able to reproduce the empirical settings.

 

[morgan]

Thanks guys. It's the classic, so 39mm it is. Mine is infrared dot-less as well. Close it up and pray I guess.

 

[petebown]

For infrared, a good rule of thumb is to use the f11 depth of field mark away from infinity. In other words, if you are focussing at infinity, put infinity on the f11 depth of field mark.

Its only a rough guess but its better than just shutting down and hoping for the best. The exact position depends on the focal length and glass types etc.

Most lenses that have an infrared mark place this somewhere between f8 and f11.

I've managed to acquire a 39mm infrared filter, but haven't made use of it yet.

 

[morgan]

Thanks for the tip Pete, I'll try that.

 

[venchka]

Hmmmmmmmmmm...I just happen to have 2 lenses sitting on a table behind my desk. So I looked and here's what I found:

Canon 135mm f:3.5, R in between f:11 & f:16.

Nikkor 50mm f:1.4, R between f:4 & f:5.6.

I suggest you find a 35mm lens with the R to use as a guide.

Good luck! show us the pictures!

 

[Bryce]

I've got a Pentax 35mm F/2 lens, and the IR focus marker is at 5.6.
Of course the correct location for the marker varies with lens design as well as focal length, but this might be a useful starting point...

 

[fstop]

I've got a Pentax 35mm F/2 lens, and the IR focus marker is at 5.6.

The IR mark on my Canon FD 35/2 is also at 5.6.