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Thread started 29 Dec 2009 (Tuesday) 10:13
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12800 ISO is NOT the same as 3200 ISO with +2 stop push PP

 
GavinTing
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Dec 29, 2009 11:58 |  #16

Panopeeper wrote in post #9283144 (external link)
The point is, that your camera, i.e. the hardware does not have those high ISOs. For example the T1i goes only up to 1600; everything higher is pushing. If you are working with raw files, you can do that pushing later, under more control, for example without clipping away the highlights.

I think the T1i goes up to 3200 natively, and then expendable to 6400 and 12800. Correct me if I'm wrong :)


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hpulley
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Dec 29, 2009 12:00 |  #17

T1i is 3200 native, at least it appears to be. Custom function for extended ISO gives you 6400 and H (12800).


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ToyTrains
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Dec 29, 2009 12:02 as a reply to  @ post 9283144 |  #18

+1
The extended ISO speeds don't exist in the camera in hardware. The camera is just multiplying the raw values to simulate the higher ISO speeds. By using extended ISO speeds you are just reducing the dynamic range at the high end.

With RAW files you really gain nothing.

On the other hand with JPG files, doing as much processing in the camera is beneficial (including setting white balance, etc) as it gets done on the raw data prior to conversion to JPG. But that's why you should just shoot RAW and not have to deal with all this in the camera :D




  
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hpulley
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Dec 29, 2009 12:07 |  #19

OK, controlled experiment in my basement's furnace room. Live view to focus on tripod once, then focus not touched. Used 15s self timer so I could run completely out of anywhere that might affect the lighting.

1/20s 3200 f/1.8 +2EV PP / 1/20s 12800 f/1.8 +0EV PP
http://www.flickr.com/​photos/hpulley/4226073​782/ (external link)
http://www.flickr.com/​photos/hpulley/4225303​777/ (external link)

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If you look, even though the NR was identical in both cases the one on the bottom at 12800 (EDIT: I messed up and had the wrong white balance on them)

You can see it here too in this example:

1/50s 3200 f/1.8 +1EV PP / 1/50s 12800 f/1.8 -1EV PP
http://www.flickr.com/​photos/hpulley/4226066​066/ (external link)
http://www.flickr.com/​photos/hpulley/4226061​974/ (external link)

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EDIT: again I'd forgotten the white balance, not sure why it was chosen differently for each one.

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IVIax
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Dec 29, 2009 12:16 |  #20

The color issue seems because you are using AWB, and if you check the exif from flicker the WB values/color temperature that the camera selected for the 2 shots are different (3200+1 = 5200K, 12800-1 = 4003K).


-Max
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Panopeeper
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Dec 29, 2009 13:17 |  #21

GavinTing wrote in post #9283368 (external link)
I think the T1i goes up to 3200 natively, and then expendable to 6400 and 12800. Correct me if I'm wrong

The highest real ISO of the T1i is 1600. The "expansion" means usually the two highest ISO settings. For example the 5DMkII goes up to 3200; 6400, 12800 and 25600 are fake, but only ISO 50, 12800 and 25600 are classified as "expansion".

This is not my idea, but I find it reasonable: there are two expansion steps, because the camera allows max. 2 EV bias. This means, that instead of using for example 25600, one can use 6400 with -2 EV exposure bias.

The following fine histograms of the raw channels show the effect of ISO faking. EVery column corresponds to one single pixel level. All pixel levels are used with ISO 1600, but only every second with 3200, every fourth with 6400 and every eights with 12800 (the ISO 6400 green does not follow this line, because both green channels are displayed, and they are "asynchron" with 6400):

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Gabor

  
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luigis
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Dec 29, 2009 13:48 |  #22

Worthless experiment. 12800 IS the same as 3200 +2...


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Volatile
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Dec 29, 2009 15:27 |  #23

Thanks hpulley for taking the time to do this, I think your results are very interesting.


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IVIax
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Dec 29, 2009 15:45 |  #24

IVIax wrote in post #9283477 (external link)
The color issue seems because you are using AWB, and if you check the exif from flicker the WB values/color temperature that the camera selected for the 2 shots are different (3200+1 = 5200K, 12800-1 = 4003K).

So OP when you come back, can you maybe fix this to see if the images will match now? (you can fix it in DPP instead of taking new shots to save some time)


-Max
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Cesium
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Dec 29, 2009 16:03 |  #25

IVIax wrote in post #9283477 (external link)
The color issue seems because you are using AWB, and if you check the exif from flicker the WB values/color temperature that the camera selected for the 2 shots are different (3200+1 = 5200K, 12800-1 = 4003K).

ding ding ding!

Again, there will be NO difference once all the variables are taken out of the equation.




  
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NaKiD ­ EyE
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Dec 29, 2009 16:11 |  #26

Panopeeper wrote in post #9282827 (external link)
1. The illumination was obviously changed between the two shots, thus the comparison is worthless.

i agree.




  
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hpulley
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Dec 29, 2009 20:41 |  #27

Sorry, I didn't check the white balance. Odd it would choose them differently on both shots. I've replaced the pictures now and will edit things above...


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IVIax
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Dec 29, 2009 20:59 |  #28

hpulley wrote in post #9286383 (external link)
Sorry, I didn't check the white balance. Odd it would choose them differently on both shots. I've replaced the pictures now and will edit things above...

It is odd... but now they look the same (or close to it) on my monitor.


-Max
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hpulley
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Dec 29, 2009 21:14 |  #29

luigis wrote in post #9283990 (external link)
Worthless experiment. 12800 IS the same as 3200 +2...

I disagree. Too many people believe everything they read without trying for themselves.


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IVIax
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Dec 29, 2009 21:28 |  #30

Actually... the 3200+2 looks slightly better than the 12800. You said you're doing NR on it ("even though the NR was identical in both cases"), at which stage?


By the way, nice experiment, even if it proves that 3200+2 = 12800, it's still nice to see it.


-Max
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12800 ISO is NOT the same as 3200 ISO with +2 stop push PP
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