bracketing

[mcmanne]

Hello,
I am trying to use the bracketing feature on my Canon 50D. While I think I understand the basic premise of using it, I would love to learn as much I can about it so;

1) How is it supposed to work?
2) in what situations should I be using it?
3) Do you recommend having the bracketng being just one stop above and below or more? and why?
4) are there any reasons NOT to use it?

any info or examples of work with it would be appreciated. Thank you so much.

Mark
www.markmanne.com

[Vagebond]

1) Automatic exposure bracketing takes three photos, exposed as you set it in AEB. The first photo is correctly exposed according to the light meter, the second is underexposed by 1/3 to 2 stops, (you set that) and the third is overexposed the same way.
a. If you're in single shot mode, you have to press shutter release three times. In continuous mode you press it once.
b. the "correct" exposure is also determined by any exposure compensation you may have set. So if you have exposure compensation at -1EV, and you bracket with a 1EV spread, you get the first exposed -1EV ("correct"), the second -2EV ("underexposed" 1 stop) and the third -0EV ("overexposed" 1 stop).

2) You can use this in difficult light conditions for example where you're not sure of exposure. Shoot three and one might be the right exposure.

Bracketing is also used in HDR (high dynamic range) photogragraphy, where different exposures are combined in one photo to produce details in the whole range. The "overexposed" had more detail in the dark areas and possibly washed out lights, the "normal" has normal detail, and the underexposed has detail in the highlights and possibly dark without details. Combine the three and you can produce very detailed photos.

If you're bracketing for HDR, use a tripod because the exposures have to be aligned over eachother.

You can see examples of HDR here in the forum: Processed and HDR - SYS, and Processed Photos - Critique.

3) One or more stops. That depends on the lighting situation and what you intend to do with the results. Experiment You could also take two series, at one and two stops, resulting in five different exposures ("correct" exposure twice).

4) No real reason not to use it except the high number of shots if you don't need/want them. Maybe the write times if you shoot RAW. But, it's up to you, ain't photography great?

This is just a start, mcmanne. If anyone wants to tell me I've got it all wrong or add useful information, please be my guest. I'm just a newbie too

[BCampbell]

Vagebond has it right.

Back in the day, bracking was a sort of "failsafe" CYA measure, or a good learning tool for beginners. Remember, with film we didn't have instant feedback, and light meters can be tricked; bracketing was a way to better ensure you had a well-exposed shot. It's even possible to merge two exposures of the same scene, if you're careful enough (much as we do now in software with layers and masks).

It was also a good learning tool; students quickly figured out the nuances of exposure by bracketing.

These days it's mostly used to make HDR images. However, I do find myself manually bracketing landscape shots now and then. The real question is, do you bracket with aperture or shutter speed? You have to be careful, both have their issues.

How many stops will depend on your scene; if the dyanmic range is high, bracket wider, if it's fairly low, you can bracket 1/2 or 2/3 stop.

[inkista]

Also, depending on the camera you have, there are different forms of bracketing other than simple exposure bracketing. The 50D can also white balance bracket, and the S90 point and shoot will focus bracket. The thinking is similar: if you aren't sure you can hit the target, having a little less and a little more adjustments and taking a set of images that covers a range of settings gives you more possibilities of hitting the target, if you don't have time to check the shot, adjust, and reshoot.

[BCampbell]

I never really understood the point of WB bracketing. If I'm taking three JPGs, I might as well just shoot one RAW.

[Vagebond]

I never heard of WB bracketing, but I know now that my next body has to have it

[i speak in math]

Originally Posted by BCampbell

I never really understood the point of WB bracketing. If I'm taking three JPGs, I might as well just shoot one RAW.

I could say the same for exposure, but I won't -- they both have uses.

WB bracketing (my pentax k20d has it) is useful if there are different color light sources in your image. Say the background is lit by tungsten but the subject by florescent. I can bracket my WB and then blend them, just like HDR for exposure, into one color corrected image.

[BCampbell]

Originally Posted by i speak in math

I could say the same for exposure, but I won't -- they both have uses.

Well, not exactly the same because if you increase exposure in software with RAW, you also increase noise. There's no change in image quality adjusting WB in RAW -- at least until you get to extreme circumstances that are unlikely to happen in the real world, whereas even overexposing a RAW file half stop introduces noticeable noise.

WB bracketing (my pentax k20d has it) is useful if there are different color light sources in your image. Say the background is lit by tungsten but the subject by florescent. I can bracket my WB and then blend them, just like HDR for exposure, into one color corrected image.

That's a great point I didn't think of. The software side of using strobe gels, basically. But you can still do this with one RAW file, without any image degradation; just expose two versions of the image with WB adjustments.

[i speak in math]

Originally Posted by BCampbell

Well, not exactly the same because if you increase exposure in software with RAW, you also increase noise. There's no change in image quality adjusting WB in RAW -- at least until you get to extreme circumstances that are unlikely to happen in the real world, whereas even overexposing a RAW file half stop introduces noticeable noise.



That's a great point I didn't think of. The software side of using strobe gels, basically. But you can still do this with one RAW file, without any image degradation; just expose two versions of the image with WB adjustments.

Just like you said for exposure and introducing noise, adjusting the WB can mess up an image as well. Lets say you expose a color to the right, that is, your red channel is up against the right side of the histogram without clipping. Warming the WB in ACR will increase the red channel, blowing it out.