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05-11-2009, 06:04 AM   #1
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Exposure bracekting for HDR

I dabble in HDR frequently enough and I love the ease of exposure bracketing on my new K20D BUT I recently noticed that when shooting a bracketed series the camera not only changes exposure but aperture as well to acheive the +/- EV.

In HDR, aperture needs to remain a constant and only exposure needs to change otherwise the change in DOF in the series makes the processed image look odd and soft.

I scoured the manual and the menus and cannot find a setting that would have caused my f/stops to change in bracketing.

Anyone got a clue what I'm talking about?

05-11-2009, 06:33 AM   #2
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Were you shooting in aperature mode?
05-11-2009, 06:52 AM   #3
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Nope, I was in Manual, using a DA 18-15mm lens.

pretty frustrating, I can't find any info to help me
05-11-2009, 06:53 AM   #4
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Depends on what shooting mode you're in; the camera will adjust whatever parameters it thinks are appropriate among the ones it's controlling automatically. Exposure is determined by shutter speed, aperture, and ISO, so adjusting aperture is a perfectly valid thing to do. You must be using Green, P or Tv?

The usual recommendation for HDR is to shoot in Av mode, since then the camera is only left to adjust shutter speed (and ISO if set to Auto).


EDIT: That's what I get for posting late. I'm surprised exposure bracketing is available in M mode...

05-11-2009, 07:01 AM   #5
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THANK YOU

Av Mode!! That's so obvious!
I was in Manual but I'll give it a go in AV, I rarely venture away from Manual mode.
05-11-2009, 07:19 AM   #6
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Well well, the only thing that changes in manual mode when I bracket is the shutter speed. So there's definitely something weird going on with your setup. I have done thousands of bracketed shots with my Pentax cameras (first with K200D and then swapped to 20D) and never had any problems with manual mode.
05-11-2009, 09:39 AM   #7
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QuoteOriginally posted by Maffer Quote
Well well, the only thing that changes in manual mode when I bracket is the shutter speed. So there's definitely something weird going on with your setup. I have done thousands of bracketed shots with my Pentax cameras (first with K200D and then swapped to 20D) and never had any problems with manual mode.
Maybe your set up is the weird one, since when I bracket in manual mode, any of the variables can change, including shutter speed.
05-11-2009, 10:30 AM   #8
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Good call Flyer

I just spoke to Pentax support and (after explaining what HDR is) I was told that auto-bracketing will change both Aperature and Shutter-speed in Manual and the only way to keep your aperature constant is in Av mode.

That's quite disappointing for those of us who like to make our own settings, I'm not a fan of Auto. I'll have to do each shot indivudually I guess. (I'll use Av mode when I feel lazy)

05-11-2009, 11:00 AM   #9
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For every person who wants aperture to remain constant but only change shutter speed, there would be someone else who wants it the other way around (eg, maybe daytime sports photography). And someone else who wants both aperture *and* shutter speed to remain constan but to have ISO vary (the most natural chocie, I'd think, for someone completely concerned about controlling both DOF and the illusion of motion). If you shoot manual and want manual control, it seems counterintuitive to use an "automatic" feature like bracketing. As another posted said, I'm surprised (shocked really) that bracketing is even available in manual mode - seems to go against the whole idea of what manual mode should be (a mode in which *you* select the settings).

So I don't see why you'd say you are someone who likes to make his own settings, but then say you're disappointed that the camera won't change them for you!

Although I wonder - despite what the Pentax people told you, maybe the behavior of bracketing in M mode is dependent on the setting of a custom option, like the one that controls the Green butotn beheavior? Eg, if you have Green button set to do Program line, then auto bracketing would do whatever it felt like, but if you had it set to do Tv shift, it would only change shutter speed, and if set to Av shift, it would only change aperture. That would actually kind of make sense...
05-11-2009, 11:22 AM   #10
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My point was that it's much better to set up your midtone shot manually, to get aperature as you want with the corresponding "mid" exposure. Then use auto bracket to hit the +/- EV in relation to your own "manually" set mid shot. Taking cloud movement/lighting changes into account it's compositionally better to be able to quickly take all three (or 5) shots.

but thank you for your last paragraph, you may be on to something there...
05-11-2009, 11:47 AM   #11
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QuoteOriginally posted by Marc Sabatella Quote
Although I wonder - despite what the Pentax people told you, maybe the behavior of bracketing in M mode is dependent on the setting of a custom option, like the one that controls the Green butotn beheavior? Eg, if you have Green button set to do Program line, then auto bracketing would do whatever it felt like, but if you had it set to do Tv shift, it would only change shutter speed, and if set to Av shift, it would only change aperture. That would actually kind of make sense...
Although, I didn't appreciate being talked down to .
You ,sir, have completely solved my problem!

Changing the green-button function in M mode to "Tv shift" did keep the aperature constant throughout all the bracketed shots.

Thanks!
05-11-2009, 08:56 PM   #12
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I have shot a number of HDRs, and what I've found is to have both your ISO and Aperature constant and shoot on a tripod.

My settings are usually either ISO 100-200 and aperature set at F8. This way, only the shutter speed varies and your depth of field remains constant. If you allow your ISO to float, you risk getting noise if one or more of your exposures is at a high ISO. You will notice the noise in the darker areas of the pic like the shadows and sometimes sky.

Check out some of my HDR samples here....

HDR Test - a set on Flickr

Alex
05-11-2009, 09:14 PM   #13
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QuoteOriginally posted by Jaredemic Quote
Good call Flyer

I just spoke to Pentax support and (after explaining what HDR is) I was told that auto-bracketing will change both Aperature and Shutter-speed in Manual and the only way to keep your aperature constant is in Av mode.

That's quite disappointing for those of us who like to make our own settings, I'm not a fan of Auto. I'll have to do each shot indivudually I guess. (I'll use Av mode when I feel lazy)
on my k100, in M and using auto bracket, aperture never changes...
05-11-2009, 09:54 PM   #14
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QuoteOriginally posted by Jaredemic Quote
Changing the green-button function in M mode to "Tv shift" did keep the aperature constant throughout all the bracketed shots.
That would explain why I haven't run into this problem - my green button was already set to Tv shift (for other reasons - makes using K/M/M42 lenses easier).

Time to start writing this stuff down on index cards for the camera bag...
05-11-2009, 11:51 PM   #15
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QuoteOriginally posted by Jaredemic Quote
when shooting a bracketed series the camera not only changes exposure but aperture as well to acheive the +/- EV.
This was a bug in the K10.
In the K20 it has been corrected.
You can now use it in M mode with constant aperture.
You have to set the Green Button mode in the menu to "Tv shift".

EDIT: I just noticed that the above has already been posted.

Last edited by blende8; 05-11-2009 at 11:57 PM.
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