Made extension on 4x5 speed to handle 5x7 lens, ...

[peter k.]

by using a black 5.25" long, 2" ABS piece of pipe. .
Is it necessary to coat it, or sand the inside of the pipe, to perhaps diminish any light reflection that may be bouncing around the inside of the pipe?
Thanks p.

 

[Dan Fromm]

by using a black 5.25" long, 2" ABS piece of pipe. .
Is it necessary to coat it, or sand the inside of the pipe, to perhaps diminish any light reflection that may be bouncing around the inside of the pipe?
Thanks p.

Absolutely. Edmund Optics sells self-adhesive flocking paper, but lining a 2" tube with it looks difficult.

Thinking of 2" tube, first things first. Assemble lens, tube, board and camera and check for mechanical vignetting by the tube. 2" may be too narrow. If vignetting isn't a problem, great! And then you can worry about flare.

 

[peter k.]

Well we took a test shot with some old Arista 200, shot at 100, and there was seemingly very little vignetting, but there seemed to be perhaps some flare, or it could be the old film.
Will take another shot, but what would be the best type of shot to take? The first one was landscape at dusk last night. Should it be of just a blank wall ect?

 

[shutterfinger]

Bright sun of mid day, landscape or any subject of your choice. I would dull the inside of the tube with fine sandpaper.

 

[Donald Qualls]

If you have (access to) a machinist's lathe, you could also thread the interior surface of the pipe (pitch not critical, you won't be screwing anything into it, but don't cut too deep; go through the skin and you'll exposed the weight-saving porous core), then spray the interior from both ends with a flat black paint (I've used Krylon Ultra Flat Black for similar applications, but couldn't find it last time I looked).

 

[peter k.]

I would dull the inside of the tube with fine sandpaper.

Interesting used a tube of sealing caulk to secure a sheet of sticky back sandpaper on to it, and it was just the right diameter to sand the interior of the 2" ABS.

So took another test shot and developed it, and there is a little vignetting around the edges but not to noticeable, and the flare we had in the negative before, is now gone since we sanded the inside of the tube.

spray the interior from both ends with a flat black paint

We may well do that, as the sanded interior of the tube is now grey, but does not seem reflective. Will examine some more test shots and see if we get anymore flare at different angles from the light, ect, will spray it.

 

[maltfalc]

for future reference or other people thinking of doing this, 3" abs pipe is a perfect fit for a pacemaker 4x5 speed/crown graphic lens board if that's what you've got. more stable and less chance of vignetting. old vhs tapes are full of screws optimised for abs. felt is easy to line abs pipe with using abs cement or acetone.