DP2x - Error Pixels in Auto Bracketing / Exposure Compensation ?

Started Oct 2, 2011 | Discussions
mxn
mxn Forum Member • Posts: 54
DP2x - Error Pixels in Auto Bracketing / Exposure Compensation ?

Hi at all,

i got a new DP2x (really like it).

On a tripod i did some pictures, take a look:

Permalink: https://imgur.com/M69K7

I did some tests, this appears if auto bracketing or exposure compensation is used, it is stronger the longer the exposure is. At least the single shots with + / - 0.0 are very clean in all light conditions.

After searching the web, it seems, this pink/yellow/green pixels are allready known, but why so strong only with these setting and also in ISO 50 ?

Johan Borg Veteran Member • Posts: 3,321
Re: DP2x - Error Pixels in Auto Bracketing / Exposure Compensation ?

It looks like it doesn't perform dark-frame subtraction when bracketing (to save time between shots?).

http://en.wikipedia.org/wiki/Dark-frame_subtraction

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nico1974
nico1974 Regular Member • Posts: 352
Re: DP2x - Error Pixels in Auto Bracketing / Exposure Compensation ?

Having exactly the same problem with the DP1 - there is no dark frame subtraction happening when auto bracketing - this is normally not a problem with shorter exposures but you really notice it after the 2s mark - had a few shot ruined recently when I realised this is happening - now only bracket manually for anything longer than 1s

Nico

mxn
OP mxn Forum Member • Posts: 54
Re: DP2x - Error Pixels in Auto Bracketing / Exposure Compensation ?

Thanks, interesting, i did not know this process...

I have done further testings (without auto bracketing)...and found following:

In long exposured RAW-files the pink/green pixels are still visible. But the JPG delveloped by the camera does filtering this completely out....

Is JPG the better mode for long exposures than RAW ?

I tried SPP4.2 and 5.1, hopefully there will be some fixes by Sigma in the future or any other workarounds....

Felix E Klee
Felix E Klee Regular Member • Posts: 384
Re: DP2x - Error Pixels in Auto Bracketing / Exposure Compensation ?

Johan Borg wrote:

http://en.wikipedia.org/wiki/Dark-frame_subtraction

Very interesting!

Now I understand the long wait after taking a picture with long exposure: Looking at the aperture, the camera must be taking a dark frame. During that time the hourglass animation is shown in the display.

I consider it unlikely that SPP doesn't make use of the dark frame. Otherwise the wait period after taking a shot would be pretty useless.

Concerning auto bracketing: The camera seems to be taking only one dark frame for the picture in the middle of the series. I just checked that with a stop watch. Naturally, for the other pictures that dark frame will not be optimal.

Good to know that it's better to do manual bracketing with long exposures!

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ArvoJ Senior Member • Posts: 1,423
Re: DP2x - Error Pixels in Auto Bracketing / Exposure Compensation ?

Felix E Klee wrote:

I consider it unlikely that SPP doesn't make use of the dark frame. Otherwise the wait period after taking a shot would be pretty useless.

SPP doesn't use dark frame, simply because dark frame is not transferred out of the camera.

Dark frame subtraction is done already in camera, before saving image Well, apparently not always successfully.

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Arvo
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Bodoh Contributing Member • Posts: 552
Re: DP2x - Error Pixels in Auto Bracketing / Exposure Compensation ?

I believe this is correct, I have observed the same. No dark frame subtraction on the + or - exposure. But there is on the center exposure.
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mxn
OP mxn Forum Member • Posts: 54
Re: DP2x - Error Pixels in Auto Bracketing / Exposure Compensation ?

Felix E Klee wrote:

Johan Borg wrote:

http://en.wikipedia.org/wiki/Dark-frame_subtraction

Very interesting!

Now I understand the long wait after taking a picture with long exposure: Looking at the aperture, the camera must be taking a dark frame. During that time the hourglass animation is shown in the display.

I consider it unlikely that SPP doesn't make use of the dark frame. Otherwise the wait period after taking a shot would be pretty useless.

Thanks, sounds very plausible. But if true it meens, developing RAWs in SPP can not recommended with most shots longer exposured than 2 seconds.

I like the camera-developing of the DP2x, but interesting to know, if Sigma can fix this in the future?

Felix E Klee
Felix E Klee Regular Member • Posts: 384
Re: DP2x - Error Pixels in Auto Bracketing / Exposure Compensation ?

mxn wrote:

Thanks, sounds very plausible. But if true it meens, developing RAWs in SPP can not recommended with most shots longer exposured than 2 seconds.

Why? I saw the camera creating a dark frame for 15s shots, and according to Arvo the dark frame is subtracted in camera. So there should be no problem here with SPP.

Only when doing auto bracketing in aperture priority mode, there is an issue: A dark frame is created solely with the exposure time of the center image.

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mxn
OP mxn Forum Member • Posts: 54
Re: DP2x - Error Pixels in Auto Bracketing / Exposure Compensation ?

Why? I saw the camera creating a dark frame for 15s shots, and according to Arvo the dark frame is subtracted in camera. So there should be no problem here with SPP.

Only when doing auto bracketing in aperture priority mode, there is an issue: A dark frame is created solely with the exposure time of the center image.

Because in the second image-compersion of this thread, I took the image in manual mode and without auto bracketing, but pink dots are visible in RAW/SPP and not with camera-JPG.

Or what other reason makes SPP fail?

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