Follow up: I just tried sticking a piece of white adhesive vinyl to the front of my lens, and it seemed to work really well, particularly as far as not letting any light leak in from gaps in it's contact with the lens rim. It's fairly opaque, and seems very tolerant of imperfect light sources, but needs a little more brightness. It also allows you to move the camera in any convenient way, so that you don't have to aim at a ceiling. The trick is to not let the adhesive contact the actual lens itself, which obviously requires that it doesn't project to the same plane as the rim. What worked for me was to lay the vinyl piece adhesive-side-up on a flat surface, and set the front of the lens tube down onto it. If I ever have another lens to calibrate, this is the method I'll most likely use. For whatever it's worth. :)
On 2014-01-02 [email protected] wrote: > On 2014-01-02 [email protected] wrote: > > > I'm trying to do calibration of a fairly wide angle lens (14mm with a > > 2.0 crop) and am finding it hard to get what appears to be even > > illumination - I certainly don't have a light source that can apply an > > even enough illumination to my ceiling. > > It's easier to get the quality of illumination you need if you don't worry > about getting too much intensity, and use a longish exposure. If I recall, I > ended up holding my camera up near the ceiling to reduce the area (and > variation in brightness) I was "photographing". > > > Does this mean that my diffusion material isn't diffusy enough (I have > > tried a white plastic trash bag)? In that case, would a Roscolux > > diffision gel be a reasonable thing to buy if I'm done trying to come > > up with a solution from household materials? > > I wouldn't say so, based on my experience. While it diffuses light nicely, it > was a little awkward to work with, not having enough mass of it's own to hold > it tight against the rim via gravity alone. I think if I were going to do it > again, I would probably try some other things first... maybe a piece of white > adhesive vinyl, of the sort used for lining kitchen drawers, etc... actually, > maybe I'll try a few things tonight and report on the results... for science. ------------------------------------------------------------------------------ Rapidly troubleshoot problems before they affect your business. Most IT organizations don't have a clear picture of how application performance affects their revenue. With AppDynamics, you get 100% visibility into your Java,.NET, & PHP application. Start your 15-day FREE TRIAL of AppDynamics Pro! http://pubads.g.doubleclick.net/gampad/clk?id=84349831&iu=/4140/ostg.clktrk _______________________________________________ Darktable-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/darktable-users
