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eastbluffs
08-07-2005, 10:03 PM
Using RAW to gain 3 stops in low light - without using a flash:

I've been using RSE (Raw Shooter's Essentials software) to adjust my RAW shots on a Canon 20D. RSE allows changing exposure up or down by 3 stops. It'll even back-fill light if desired. To my eye, it looks just like it would if I had selected the higher exposure originally, without the disadvantages of a higher exposure setting.

Adjusting down (on an overexposed shot) seems to have a little less detail, but it seems that the 20D keeps the same, or possibly even more detail when underexposed!

Are there any disadvantages to using his method?

It sure beats accepting either the grainy ISO 800 or 1600, or having blury photos from inadequate shutter speed.

My hand-holding seems to get slightly blurry anywhere below about 1/90th when trying to stay still, 1/60th when really trying, and slightly blurry below 1/250th with a normal quick shot.

I'd love to hear about some similar tricks to reduce the disadvantages of high exposusure while achieving the ultimate result of a better photo?

ReF
08-07-2005, 11:28 PM
just how much underexposure are you refering to? 1/3 stops 2/3 stops, more?

if you underexpose and have areas in your shot that are already dark and the histogram curve is cut off at the left side, you are losing "shadow" details. i've heard many time that the best thing to do is to "expose to the right" of the histogram without blowing the highlights so you get as much shadow detail as possible. but i tried it and found that technique has it's own problems.

also that if you underexpose and then bump up the exposure in RAW processing to the "correct" exposure, there will be more noise than if you shot at the correct exposure in the first place. but if you are talking about increasing shutter speed and underexposing just a tad while keeping the ISO at say 400, then i guess there will be less noise after RAW processing than if you went up to ISO 800 and gained more shutter speed than needed.

eastbluffs
08-08-2005, 12:37 AM
just how much underexposure are you refering to? 1/3 stops 2/3 stops, more?

if you underexpose and have areas in your shot that are already dark and the histogram curve is cut off at the left side, you are losing "shadow" details. i've heard many time that the best thing to do is to "expose to the right" of the histogram without blowing the highlights so you get as much shadow detail as possible. but i tried it and found that technique has it's own problems.

also that if you underexpose and then bump up the exposure in RAW processing to the "correct" exposure, there will be more noise than if you shot at the correct exposure in the first place. but if you are talking about increasing shutter speed and underexposing just a tad while keeping the ISO at say 400, then i guess there will be less noise after RAW processing than if you went up to ISO 800 and gained more shutter speed than needed. My samples were a full stop or more under. Some shots were over 2 stops under. I'll have to look closer to see how those compared. I suppose a concerted effort at experimenting with different settings would be the best way to tell.

It was an accidental discovery. I was alternatively shooting against bright backlighting and kept forgetting that I had the exposure slider down. Then after correcting it I kept getting motion blur and thought "well, maybe I'll just correct it later". I decided to experiment around so took about 100 shots in varying settings, many of the same thing.

It was in a bar and I was trying to practice getting "sly shots" without flash. So some I had to push the ISO way up and accept lower exposure just to keep the shutter speed reasonable.

Later in RSE; I was pretty pleased with the results. It occurred to me it might be a good thing to learn more about, and could become a nice trick to know about.

Went to a party yesterday and took lots of slightly underexposed shots using manual settings. Then my RSE decided to stop working (my laptop power quit and somehow upset RSE) and re-installs won't work. So; further experimenting will have to wait until I upgrade to XP. Maybe tomorrow.

I haven't gotten into the "histogram" readout. Thanks for the tip, will look into it. I'm sure histogram reading is a whole new chapter to learn about.

One last comment; I just took some outdoor just-after-sunset shots using a flash. The background is all dark and dingy - more so than it looked to my natural eye. I was thinking that slightly underexposing a shot (even with flash) then pushing everything up later so the subject is correct would be a good way to correct for this.

Bluedog
08-08-2005, 04:54 AM
I've had pretty good success with RSE also. One thing to remember is to set the detail extraction down to around - 20 ~ 35 for best results.

tim11
08-09-2005, 04:41 PM
Does this trick work in TIFF format also?