2009 September 20th, 18:26
Weird artifacts - DIY adapter
I've built dof adapter (static), using Canon EE-S focusing screen. Raynox DCR-250 works as a macro, im using m42 lenses. Everything would be nice, but im getting some weird stripes and patterns on screen (please ignore vignetting and dirt on GG).
I've uploaded some samples with description of settings here:
www.qmite.com/problem/pics.html (click pictures for full res versions).
I know that on higher aperatures Canon EE-S tend to show its microlens structure, but im getting it even on f/2.0. Theres actually 2 types of artifacts:
One (seen on pics. 1-18) is dependent on aperature (its visible even at f/2.0 tho), and can be reduced by rotating focusing screen by some angle. At some point they are almost invisible (pics. 15, 18) but if you look closely You'll find them. Other way I discovered is unzooming camera a bit - having borders which i need to crop (and loose some resolution...), but they ALMOST dissapear. Third way is to defocus camera a bit.. but it looses to much sharpness (pics. 10,11).
Second pattern (horizontal lines) is visible when lens is out of focus, at every aperature even 2.0. And its not really dependent on zooming camera or rotating focusing screen (pics. 19-23 and 32-35).
I thought it may be raynox, but i can see this patterns (at least second type) even with bare eyes (without raynox/camera). I tried to change lenght of whole adapter (distance from hv20 to gg), it changes lines but they never dissapear completly.
Could it be that I've damaged focusing screen while building adapter (i put it on and off like million times, sometime by force), or when I cleaned it with distilled water? I'm out of ideas... :/
Anybody have similar problems or know the solution? I know many people use EE-S, seen lots of footage and no one seems to have problem with it.. (Twoneil's footage looks nice, and judging by his "domino effect" video he uses a lot EE-S screens;d).
I've spend few months collecting parts, building dof adapter and rails... getting pretty good picture with it, but this artifacts makes it unusable. Help!;]
2009 September 20th, 22:15
looks like a finger print on one of the lenses. I dont know, I don't use static adapters for the dirt reasons on the gg
2009 September 21st, 04:29
I used many different lenses, and its surely not fingerprint:]
2009 September 21st, 04:45
Previously geeking out over 2/3" Scarlet. Scarlet-X...not so much.
I guess it's some kind of interference in the EE-S microlenses, i guess there's not much you can do about it... a vibrating adapter would probably hide those. My DIY uses EE-S too, but i've never noticed that kind of a pattern.
Originally Posted by qmite
2009 September 23rd, 05:30
yes, i thought that first artifact could be a moire effect of hv20 sensor and gg's microlenses as it changes with rotating gg
but second type - patterns when slr lens is defocused?.. its visible even without camera
and i wonder why I'm the only one seeing this problems with ee-s :/
2009 September 23rd, 13:14
I've seen the second artifact in my 20d viewfinder--it has to do with the pattern of the groundglass. Unlike an actual piece of glass which has been ground, these SLR GGs have a specific pattern to them, and are etched with a laser. The pattern is designed to give the best overall brightness, but it makes the bokeh less natural and gives this sort of repeating line artifact.
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