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Author Topic: Michael Reichmann, ETTR and Oly OMD EM5  (Read 16235 times)
ZoranC
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« on: June 27, 2012, 12:26:16 AM »
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Now that Michael is using EM5 I am wondering could he share with us his experiences using ETTR on it.

For start, I am wondering what is better to use on it to make sure one didn't overexpose, shadow/highlight blinkies or histogram of all channels? Or both?

Next, when using blinkies, what values would be best for Histogram Settings to indicate over/under exposure and why?

And when it comes to metering when one would want to use Spot Highlight and when one wouldn't want to use it?

Lastly, I am interested in input on Auto Gradation. From what I understand it affects metering (it underexposes by 1/3 of stop) even when one is shooting only RAW. Thus when RAW shooter would want to use it over Normal and vice versa, if ever? And how use of it would interact with ETTR efforts?
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michael
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« Reply #1 on: June 27, 2012, 05:45:46 AM »
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No need to over complicate things. Use the blinkers because they are easy to judge at a glance. The highlights are the only important ones unless you are doing lighting on a set and can add fill. I leave the highlight setting at 255.

Just expose so that nothing important blinks, (go over, then back off a touch) and you have optimum raw exposure. Same applies to cany camera with a highlight warning.

Michael
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ZoranC
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« Reply #2 on: June 27, 2012, 12:47:07 PM »
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No need to over complicate things. Use the blinkers because they are easy to judge at a glance. The highlights are the only important ones unless you are doing lighting on a set and can add fill. I leave the highlight setting at 255.

Just expose so that nothing important blinks, (go over, then back off a touch) and you have optimum raw exposure. Same applies to cany camera with a highlight warning.
Thank you! I am a big fan of KISS approach, but for a sake of better understanding please allow me few more questions.

It is my understanding (please correct me if I am wrong) that blinkies, just like histogram, depend not on data in RAW but on data in JPG preview that gets saved with RAW, and in turn JPG preview depends on settings for Picture Mode, Saturation, Contrast and Gradation. Thus am I correct in understanding that one would want them set to something like Muted, toned down Saturation and Contrast, and Normal Gradation while deciding what optimal RAW exposure is? If yes would ETTR at such settings introduce bigger chance of later blowing highlights in the post-processing? I am asking because I think I have seen a shot taken with ETTR and Muted that was not blown yet became blown once one applied iEnhance in post to it's RAW.
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« Reply #3 on: July 11, 2012, 10:40:38 AM »
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Thank you! I am a big fan of KISS approach, but for a sake of better understanding please allow me few more questions.

It is my understanding (please correct me if I am wrong) that blinkies, just like histogram, depend not on data in RAW but on data in JPG preview that gets saved with RAW, and in turn JPG preview depends on settings for Picture Mode, Saturation, Contrast and Gradation. Thus am I correct in understanding that one would want them set to something like Muted, toned down Saturation and Contrast, and Normal Gradation while deciding what optimal RAW exposure is? If yes would ETTR at such settings introduce bigger chance of later blowing highlights in the post-processing? I am asking because I think I have seen a shot taken with ETTR and Muted that was not blown yet became blown once one applied iEnhance in post to it's RAW.

I think Michael is advocating for a simple and common-sense approach.  First deliberately overexpose, and then back off a bit.  Don't make ETTR harder than it needs to be. 

If you really want to get precise about this there are convoluted methods for setting white balance that may help you to get closer to some theoretical maximum exposure, but it is complicated and annoying. 

ETTR isn't extremely helpful in a very high dynamic range environment (where the histogram exceeds the range of the scale on both left and right).  Think of ETTR as more helpful when you have a very narrow hump in the middle of your histogram, with no extra lobes to the right.  In that case (most commonly repeatable in dense fog) in preparation for RAW post-processing, you want to move it over to the right side, but don't try to get it so close that you are likely to accidentally clip because your histogram is using the jpg image for the highlight warning.  In that case you are courting disaster. 
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richarddd
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« Reply #4 on: January 02, 2013, 01:43:15 PM »
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If changing aperture and shutter speed isn't enough to get to the point where there are blinkies (perhaps because of desired DOF or lack of blur), does it make sense to increase ISO?
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ErikKaffehr
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« Reply #5 on: January 02, 2013, 01:50:15 PM »
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Hi,

Increasing ISO is a bad idea. The reason behind ETTR is to maximize exposure. You want to capture as many photons as possible.

Best regards
Erik


If changing aperture and shutter speed isn't enough to get to the point where there are blinkies (perhaps because of desired DOF or lack of blur), does it make sense to increase ISO?
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ErikKaffehr
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« Reply #6 on: January 02, 2013, 02:01:04 PM »
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+1

Erik

No need to over complicate things. Use the blinkers because they are easy to judge at a glance. The highlights are the only important ones unless you are doing lighting on a set and can add fill. I leave the highlight setting at 255.

Just expose so that nothing important blinks, (go over, then back off a touch) and you have optimum raw exposure. Same applies to cany camera with a highlight warning.

Michael
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digitaldog
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« Reply #7 on: January 02, 2013, 02:02:08 PM »
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Increasing ISO is a bad idea.

On some cameras yes, on some, it's the same as ETTR if handled as such.
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richarddd
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« Reply #8 on: January 02, 2013, 02:40:10 PM »
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Increasing ISO is a bad idea. The reason behind ETTR is to maximize exposure. You want to capture as many photons as possible.
Increasing ISO does not change the amount of light coming into the camera. Assume you've already set optimal aperture and shutter speed.

http://www.luminous-landscape.com/forum/index.php?topic=56906.40 suggests the answer to the general question regarding increasing ISO once you've done all you can with exposure is "it depends" on the camera, which is digitaldog's answer.  I'm wondering what the answer is for the E-M5

In my tests so far, increasing ISO at worst doesn't hurt and at best clearly helps, provided that I don't go above 1600.  From what I've read, values between 200 and 400 should be avoided.  Before drawing any conclusions I'd like to hear from others, as I might not be testing properly, ignoring important cases, etc.

Might dynamic range be an issue in addition to noise, or does a change in one make a corresponding change in the other?
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Vladimirovich
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« Reply #9 on: January 02, 2013, 03:33:22 PM »
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Increasing ISO does not change the amount of light coming into the camera. Assume you've already set optimal aperture and shutter speed.

but bigger gain (it it is done not using tags - like GH3 does for ISO above 6400) may result in raw data clipping sooner than lower gain...  however if you claim that you have already the best aperture and shutter speed set and you are not ETTR fan (= you do not want more light, even you have room for that) then based on your particular camera ( Canon-like sensors) you might want to increase the gain to deal w/ lower read noise... is it what you are trying to assert ?
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richarddd
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« Reply #10 on: January 02, 2013, 03:52:55 PM »
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but bigger gain (it it is done not using tags - like GH3 does for ISO above 6400) may result in raw data clipping sooner than lower gain...  however if you claim that you have already the best aperture and shutter speed set and you are not ETTR fan (= you do not want more light, even you have room for that) then based on your particular camera ( Canon-like sensors) you might want to increase the gain to deal w/ lower read noise... is it what you are trying to assert ?
What I'm asking (for the E-M5) is, assuming I've set optimum aperture and shutter speed, is it a good idea in terms of image quality to increase ISO to just below the clipping point (where clipping is determined by blinkies, as Michael stated), so long as you don't go above 1600? 

By optimum aperture and shutter speed, I mean letting in as much light as possible, consistent with desired DOF and blur. I would hope even ETTR fans don't set shutter speeds so low that they get subject or camera blur or aperture so wide they don't get appropriate DOF, but in any event that's not something I want to do.

If this strategy is best to get lower read noise, are there any countervailing issues that would suggest it is not a good idea?
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« Reply #11 on: January 02, 2013, 04:11:10 PM »
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I don't know the answer, but I am going to speculate a bit. 

As has been mentioned, assuming you keep the aperture and shutter the same you aren't actually increasing the amount of light entering the camera.  What you are doing is boosting the signal (with it the noise) so that it moves the data into the brighter half of the histogram--towards the right.  I think this would be advantageous because you would be moving the data into the region of the histogram where the sampling rate is higher.  The signal to noise ratio would be the same, but the gradations of light sensitivity would be finer. 

I think that you will not see a difference in noise-performance because boosting in camera (increasing ISO) or boosting in post processing (exposure slider in ACR) achieve very similar results.  With that said, I have come full circle because one of the main purposes of ETTR is to increase the signal to noise ratio.  Your strategy doesn't accomplish an increase in SNR. It only allows you to capture more tonality within the dynamic range that is present. 

There is no magic here. If you are working at 1600 ISO and are underexposing by 3 stops, you are not much worse or better off than going to 12,800 ISO and having the "correct" exposure (aside from the fact that you will recover some shadow detail at 12,800 and it will be total crap).  The details of these relationships are not precisely the same for all manufacturers, but generally speaking these relationships hold true. 

So you get half-credit for your approach within the limitations you describe.
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Vladimirovich
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« Reply #12 on: January 02, 2013, 04:58:32 PM »
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By optimum aperture and shutter speed, I mean letting in as much light as possible, consistent with desired DOF and blur.

define possible about exposure time = possible based on clipping or possible based on subject moving/stabilization/etc

if the situation imposes the limit on how long your exposure can be and you are not close to clipping @ lower gain  then you might want (based on your camera) increase the gain to lower read noise - so you test your camera using the tools available to see what is the max gain after which there no advantage in read noise reduction.
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AFairley
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« Reply #13 on: January 02, 2013, 06:00:45 PM »
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This is a case where the proof of the pudding is in the eating and the answer can be empirically shown by shooting both ways (iso boost or no iso boost) and seeing which one PPs best, which, after all, is what you are after.
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richarddd
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« Reply #14 on: January 02, 2013, 06:20:08 PM »
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define possible about exposure time = possible based on clipping or possible based on subject moving/stabilization/etc
Start at high shutter speed.  Decrease until first of (1) clipping and (2) subject moving/stabilization/etc

if the situation imposes the limit on how long your exposure can be and you are not close to clipping @ lower gain  then you might want (based on your camera) increase the gain to lower read noise - so you test your camera using the tools available to see what is the max gain after which there no advantage in read noise reduction.
Which available tools?

Aren't there are issues besides read noise, such as shot noise and dynamic range?
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richarddd
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« Reply #15 on: January 02, 2013, 06:25:41 PM »
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This is a case where the proof of the pudding is in the eating and the answer can be empirically shown by shooting both ways (iso boost or no iso boost) and seeing which one PPs best, which, after all, is what you are after.
As I mentioned above, testing so far shows either no harm or improvement in increasing ISO up to 1600.  I set ISO to 1600, set aperture and shutter speed just below having some areas clip, then retook the same shot at ISO 200. In LR4 I used the exposure slider to increase by 3 stops, which matched brightness levels, then looked at both pictures.

I'm concerned that there are cases I'm not testing (perhaps higher dynamic range, perhaps others) or that I'm otherwise missing something.
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richarddd
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« Reply #16 on: January 02, 2013, 06:32:38 PM »
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I think that you will not see a difference in noise-performance because boosting in camera (increasing ISO) or boosting in post processing (exposure slider in ACR) achieve very similar results.
Is there any reason to believe boosting ISO and boosting in post will achieve similar results?  I've seen examples with some cameras showing quite different results. For example, the second post in this thread http://www.luminous-landscape.com/forum/index.php?topic=56906.0 Alas, that thread deals with cameras other than the E-M5
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Vladimirovich
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« Reply #17 on: January 02, 2013, 08:07:12 PM »
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such as shot noise

you can't do anything about shot noise because you can't increase exposure time (you are bounded by either raw data clipping that you do not want or your subject movement or your lens/sensor stabilization or something else) and you can't increase aperture - your own words... so you can't get more light = your shot noise is what it is... the only chance you have is to pour some liquid nitrogen to cool your sensor  Roll Eyes or to may be reduce the read noise (if your camera has such sensor/adc/firmware) by increasing the gain (that is only if your exposure time is limited not by clipping).

and dynamic range?

what about DR ? you were in a situation when you can get more exposure time to get more light... it is either clipping or subject moving or something else... if it is not clipping you can try to lower read noise affecting your deep shadows by applying a bigger gain (but test your own camera and converter).
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Vladimirovich
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« Reply #18 on: January 02, 2013, 08:14:03 PM »
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Is there any reason to believe boosting ISO and boosting in post will achieve similar results?
certainly, at some point it makes no sense to further increase the gain in camera (unless you need in camera JPG for whatever reason)... but it is specific to a camera model (and may be even a specific unit) and then probably not all raw converters were created equal.
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Vladimirovich
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« Reply #19 on: January 02, 2013, 08:15:55 PM »
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Which available tools?


I think you were pointed to such tools more than one time in the past.
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