Technical question about exposure bracketing.

[Mjollnir]

I just started playing around with this feature on a Panny GH2, which offers up to (I think) 7 or 9 different exposures to be bracketing.  Never having experimented with this before, but now really happy with the potential, the following questions occurred to me:

A.  Is there some reason (software limitations, mechanical difficulty, etc...) that bracketing must be evenly and sequentially done?  IOW, I can set it for -2/-1/0/+1/+2, for example, but why not -3/0/+1/+2.5?

B.  If I set up for a bracketed shot, and have EV set at something besides 0, for example, will the camera shoot with a bias towards whatever EV is set at?  Specifically, if I have EV at, say, -1, with the camera then treat that -1 EV as the 'zero point' if I've set up bracketing for -2/-1/0/+1/+2?

Thanks!

[Bart_van_der_Wolf]

I just started playing around with this feature on a Panny GH2, which offers up to (I think) 7 or 9 different exposures to be bracketing.  Never having experimented with this before, but now really happy with the potential, the following questions occurred to me:

A.  Is there some reason (software limitations, mechanical difficulty, etc...) that bracketing must be evenly and sequentially done?  IOW, I can set it for -2/-1/0/+1/+2, for example, but why not -3/0/+1/+2.5?

Hi,

You typically do not want to exceed bracket intervals of more than 1-2 stops in between, to avoid noise differences becoming a problem with the blending or tonecurve reconstruction. The longer exposed frames will have lower shot-noise. There is no absolute obligation to use even spacing between the brackets, other than convenience and for avoiding jumps in noise performance.

B.  If I set up for a bracketed shot, and have EV set at something besides 0, for example, will the camera shoot with a bias towards whatever EV is set at?  Specifically, if I have EV at, say, -1, with the camera then treat that -1 EV as the 'zero point' if I've set up bracketing for -2/-1/0/+1/+2?

I think that on most cameras, the whole bracketing series will have a -1 EV correction.

Cheers,
Bart

[meyerweb]

HDR isn't the only reason to bracket, so there might be times you wanted a larger gap, I suppose.  But I don't think there's any technical reason why a camera couldn't be programmed to allow non-symmetrical intervals. But I'm not aware of any that do. But if you bracket, say, 5 exposures at 1/2 stop intervals you could then pick the -2, 0, and +.5 exposures to work with if there's a reason for that.

And yes, if you set EC to a value other than zero the bracketed exposures are based around that as the center point.

[Tony Jay]

HDR definately is not the only reason to bracket.
Just getting a good ETTR exposure often needs a few brackets - this is especially so if one using a relatively new camera and still getting to grips with its sensor characteristics.
If one is bracketing for the purposes of HDR evenly spaced exposures generally of one stop are the most practical way to go about it. One can get away with bigger gaps in exposure sometimes but one stop is probably best.

Regards

Tony Jay

[Mjollnir]

Thanks for the replies, everyone.

I'm using HDR Efex Pro 2 to stack images I've bracketed, but other than that I do any and all PP outside of the program.  It came with the NIK suite, so it's convenient, but after having played around with it, there is a LOT of useless/really bad taste thrown in that just isn't necessary or intersting.

Hadn't considered doing it for ETTR, because I simply don't use the technique for what I do, but it's an interesting idea.