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03-14-2012, 08:06 AM   #1
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Exposure Bracketing: Why not faster?

I have a K20D and a K-5, and I keep wondering about this non-feature:

When I shoot with exposure bracketing, i.e. take a series of shots at different EVs of the same scene, why does the camera move the mirror between each of the pictures instead of taking ONE measurement and then just lock the mirror up, shoot the 3 or 5 images, and only then lower the mirror again? Wouldn't that be much faster? Or are the electronics (sensor) so "slow" that they can't handle the gained speed?

To clarify: I am aware that there are more moving parts involved, e.g. focussing and aperture. But my point is: The camera could offer a special "fast bracketing" mode, in which it assumes a fixed aperture and fixed focus for the entire bracketed sequence, and only varies ISO and/or exposure time. I'm pretty sure the camera mechanics can handle that, since it's already partly possible with the mirror-lock feature (i.e shutter independent from mirror, focus and aperture). Meaning, it's all just a question of software.

(Man, as a software developer, it really bugs me that camera firmwares aren't open sourced, and that the makers are so closed up about their software dev process)


Last edited by tempelorg; 03-14-2012 at 08:56 AM.
03-14-2012, 08:45 AM   #2
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it only takes a send to flick off five images, what difference will it make?
it is just the way the camera works is my guess
03-14-2012, 08:49 AM   #3
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But in that ~1 second for the 3 or 5 shots the object might have slightly moved, and that annoys me.

The other day I tried to take such imgs for HDR composition, in a darkened room with a video projector. I tried to get the speaker (dark) with the projected img (bright) on the same picture, so I needed the exposure bracketing. But the fact that the speaker moved slightly during this process makes creating the HDRs quite difficult. Had the camera taken the imgs in faster succession, this would be a much smaller issue.
03-14-2012, 08:59 AM   #4
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I believe that having to drop the mirror down each time when doing bracketing is stupid, yes. It should just flip the mirror up, and take all the bracket shots, then drop the mirror.

I imagine continuous drive should ALSO do this, except I believe continuous drive also drops the mirror after each shot.

03-14-2012, 09:15 AM   #5
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Well, if you tried to take a shot of the dark speaker and the brigh projector in a darkened room, having the mirror up doesn't matter at all> The shutterspeed would be so low, that having the mirror up would not have made any significant difference in speed.

And Jin, you cannot track a moving subject with the mirror up, as you cannot keep on composing. So the mirror needs to come back down.
03-14-2012, 09:27 AM   #6
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Just a little more info, if you are in live view the mirror doesn’t come down. It can take the photos at the max speed that the shutter speed and the speed of the shutter can go. There is also no mirror vibration if you use live view.

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03-14-2012, 09:52 AM   #7
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QuoteOriginally posted by Macario Quote
Well, if you tried to take a shot of the dark speaker and the brigh projector in a darkened room, having the mirror up doesn't matter at all> The shutterspeed would be so low, that having the mirror up would not have made any significant difference in speed.
I wonder how you can come to that conclusion. This is a K-5 after all, and I used a f/2 lens, ISO 6400, even handheld, and all the shots were 1/30 at most. So, in that regard, I am pretty sure that avoiding the extra mirror and other mechanics would indeed shorten the overall time.
03-14-2012, 09:57 AM   #8
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QuoteOriginally posted by DAZ Quote
Just a little more info, if you are in live view the mirror doesn’t come down. It can take the photos at the max speed that the shutter speed and the speed of the shutter can go.
Ah, good point! I forgot about trying that.

I tried now, and I find it just as fast as with the non-live view mode. If I take 5 shots per bracketing, it takes about the same time, i.e. a bit more than a second. Maybe it's the shutter reset that takes so much time.

03-14-2012, 10:09 AM   #9
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The mirror should be just as fast as the shutter, so the main issue here is noise and vibration. I guess some might like the fact that the image flickers in the vf, though. As far as I recall the Nikon D3x behaves the same way
03-14-2012, 10:14 AM   #10
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QuoteOriginally posted by tempelorg Quote
I wonder how you can come to that conclusion. This is a K-5 after all, and I used a f/2 lens, ISO 6400, even handheld, and all the shots were 1/30 at most. So, in that regard, I am pretty sure that avoiding the extra mirror and other mechanics would indeed shorten the overall time.
What are all your shutterspeeds thenin this bracketing series. Then we can easily calculate the extra time the mirror takes
03-14-2012, 10:23 AM   #11
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QuoteOriginally posted by Adam Quote
The mirror should be just as fast as the shutter
What makes you believe that? I've taken apart SLRs 30 years ago and have some understanding of the shutter mechanism. The "opening" process of the shutter is about what the flash sync time on it is, and then there's the time it takes to reset it. Both together should not take a 1/5 second, it should be much less.

Or look at it this way: The new Sony a77 is so fast with its 10 shots/s BECAUSE it doesn't have a moving mirror, or so they say. Read the reviews.

All this supports my assumption that the mirror slows down the bracketing time. What is your argument against it?

Clarification: Maybe you confuse cause and effect in this relationship: If the mirror is the slowest part (as I claim), then there's no use in making extra efforts to make the shutter faster, since _usually_ one won't gain any overall speed from it. The question I pose in this thread is: Could it be that the shutter is faster anyway, and if so, couldn't this special application (shooting with fixed Aperture and fixed Focus) speed up the bracketing shots thus?
03-14-2012, 10:34 AM   #12
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QuoteOriginally posted by tempelorg Quote
What makes you believe that? I've taken apart SLRs 30 years ago and have some understanding of the shutter mechanism. The "opening" process of the shutter is about what the flash sync time on it is, and then there's the time it takes to reset it. Both together should not take a 1/5 second, it should be much less.

Or look at it this way: The new Sony a77 is so fast with its 10 shots/s BECAUSE it doesn't have a moving mirror, or so they say. Read the reviews.

All this supports my assumption that the mirror slows down the bracketing time. What is your argument against it?

Clarification: Maybe you confuse cause and effect in this relationship: If the mirror is the slowest part (as I claim), then there's no use in making extra efforts to make the shutter faster, since _usually_ one won't gain any overall speed from it. The question I pose in this thread is: Could it be that the shutter is faster anyway, and if so, couldn't this special application (shooting with fixed Aperture and fixed Focus) speed up the bracketing shots thus?
Did you know that the new Canon 1D-X can take 14fps, with mirror going down after everyshot? So it not the mirror that is the biggest issue, it is the shutter
03-14-2012, 02:08 PM   #13
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QuoteOriginally posted by tempelorg Quote
The new Sony a77 is so fast with its 10 shots/s BECAUSE it doesn't have a moving mirror, or so they say.
I can't recall any that have said that. What they have said is that it allows the AF to function so fast because there is no moving mirror.
03-14-2012, 02:41 PM   #14
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QuoteOriginally posted by Macario Quote
Did you know that the new Canon 1D-X can take 14fps, with mirror going down after everyshot? So it not the mirror that is the biggest issue, it is the shutter
More to the point, it's a decision made by the manufacturer. In the case of Pentax, they decided to go with a shutter that would hit some 7 fps, so there isn't much point in putting in a mirror mechanism that would go faster.
03-14-2012, 04:11 PM   #15
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@templeorg, please read my studies about possible shutter-induced vibration in the K-5 and you'll know everything you'll ever need, and then some. The mirror is NOT slowing down exposure bracketing shots. It is not the slowest part as you claim. Or loudest. Or the one causing most vibration.
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