Re: [Gimp-user] Add frozen object from short exposure frame to long exposure frame

[Casey Connor <gimp-user-list caseyconnor org>]

> stationary artificiallighting is provided from the people who work at these caves as well).So my plan is to 
> use my Rokinon 12mm f2.0 with my Sony A6000 on a tripod and setit to max aperture and long exposure, with 
> maybe ISO of about 400 to 800. Dothose settings sound about right to get some good low-lit cave pictures?

For the long exposure, use the lowest native ISO your camera has (don't 
use any "extended" ISO values your camera might offer.) There is nothing 
to be gained by going to 400 or 800 except a shorter exposure time 
(which can be relevant, but in your case sounds like it isn't). For the 
fast one, I'd use the widest aperture the lens has, the longest shutter 
speed you can afford given the motion you want to capture, and then set 
the minimal ISO to get the exposure.

> Wouldthere be any reason to lower the aperture?

There might be -- if you have the luxury of a tripod and long exposures, 
you can narrow the aperture either to get better sharpness from the lens 
(most, but not all, will be sharpest a couple stops up from the widest 
aperture -- you can research the lens online; unfortunately dxomark.com 
doesn't cover that lens), or to get more depth of field. f2 is going to 
be pretty shallow. Might be cool, might not.

You might look into image averaging (usually taking the median, 
actually, as opposed to the mean)... I was just experimenting with a 
GIMP workflow for that and it's pretty great. It's useful for taking 
low-light pictures without a tripod, especially if you want to use 
higher shutter speeds.

You also might think about longer focal length lenses. I love 12mm, and 
that's what I would take first in your situation, but if any of the 
geometry of the caves allows for farther shots (i don't know how big 
they are), you can use the telephoto effect to enlarge the background... 
it can be a neat effect 
<http://media.gettyimages.com/videos/man-walking-in-front-of-skogafoss-waterfall-iceland-video-id98632542?s=640x640>. 
Also, if you don't have many options of where to set up for a shot, e.g. 
because you're straddling a stream and balancing on a boulder or 
whatever, having a zoom gives some flexibility.

-c