Gonz wrote:
I'm using the K-5, considered one of the ISO invariant cameras. Here
are the images:
Properly exposed with ISO1600:
https://www.flickr.com/photos/66982297@N02/32559204535/in/dateposted-public/
+4 compensation at ISO 100:
https://www.flickr.com/photos/66982297@N02/32179978780/in/dateposted-public/
The colors are where the extreme differences are. The histogram
actually goes to the right at about the same spot.
It looks like the contrast is set way higher in the ISO 100 image. Did
you perchance try autotoning? What about adjusting your black levels?
On Fri, Jan 27, 2017 at 5:28 PM, Larry Colen<l...@red4est.com> wrote:
Gonz wrote:
Ok. I've done some experiments to test this whole ISO invariance
subject, which some ascribe almost mythological healing powers to
underexposed images. I'll reveal one pair of experimental images
after I have my methodology down. Hence this post. The results were
so surprising, that it made me question my methodology.
Which body are you using?
Here is what I did.
1. take an image with ISO 1600 properly exposed. Use manual and set
shutter and aperture for image result that takes up most of the
histogram (avoid blowing highlights)
2. take a second image with same shutter and aperture but at ISO 100.
I.e. 4 stops underexposed.
3. Import into lightroom, compensate +4 exposure on the underexposed
ISO 100 image.
My lightroom has a limit of +4, hence the selection of 100 and 1600
for ISO values.
Images should look roughly the same if this methodology is right? Are
the ISO values correct? 100 * 2^4 = 1600, or is this wrong?
It looks right to me. Before I had heard of ISO invariance, I sort of
discovered it accidentally. When not shooting action, and when I don't want
to bother chimping the histogram for every shot, or when I'm shooting wide
dynamic range images I'll just bracket, generally three exposures +/- 2 or
three stops.
My preferred auto exposure mode is usually Tav. I noticed that when
bracketing in Tav, after correcting my exposure in lightroom, I generally
couldn't see much difference between the three shots. Do note that in the
"over" shots I'd get a bit more clipping, and in the "under" shots, I'd
sometimes get a bit more noise in the shadows. Also, there seem to be some
nonlinearities in the way LR processes files, so they wouldn't always all
come out exactly the same after processing, but yeah, modulo some channel
clipping, they'd look pretty close.
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Larry Colen l...@red4est.com (postbox on min4est) http://red4est.com/lrc
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