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  #16  
Old 4th November 2014
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Re: Is this taking Expose To The Right (ETTR) too far?

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Originally Posted by birdboy View Post
It has occurred to me that a possible disadvantage of optimum ETTR may affect autofocus systems. The examples he has show has significantly reduced contrast so will the AF systems, particularly in the mFT lenses, struggle to get focus?
Hmm, not sure about that. The contrast of the scene itself won't have changed, so I think the contrast is still there, it's just that the histogram has moved up the response curve. But doesn't A/F work at a different aperture to the taking aperture? And the shutter speed shouldn't affect it as focusing is performed with the sensor exposed.

The problem may well be that a black cat with a black background, or a white rabbit in snow, is already a low contrast scene, and so the A/F might well struggle whatever the camera exposure settings. So I don't think the A/F issue is peculiar to this way of working.
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  #17  
Old 4th November 2014
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Re: Is this taking Expose To The Right (ETTR) too far?

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Originally Posted by srtgray View Post
ETTR is completely wrong for digital. If anything one should underexpose.
Definitely a big NO!

Half the detail in the image is in the brightest stop. This means that if you underexpose by one stop, you've only captured half the detail available for the image. Underexpose by two stops and you've only captured one-quarter of the detail.

If you then 'spread' the histogram in PP, in order to attempt to get a full tonal range, you run the risk of posterisation.

The late-great Bruce Fraser sums it up well in his 'Real World Camera Raw Adobe Photoshop CS2' book (pages 6-8). It may be old(ish), but like all his books in this series is well worth getting.

Jim
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  #18  
Old 4th November 2014
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Re: Is this taking Expose To The Right (ETTR) too far?

When the E-M5 came out there was a lot of discussion on "the other forum" about ETTR amd Uni-White Balance (effectively ETTR for each individual colour in the histogram by means of setting a custom white balance). The sole purpose is to overcome limitations in the sensor and the non uniform tone/colour balance of the picture being taken by adjusting the exposure/colour to make maximum use of the sensor's range.

This is all well and good in theory and can in practice (in some cases) make a difference. Knowing that you have wrung the utmost sesitivity out of your equipment to get the most detail in your final image does please some people.

The downside is that ETTR does mean increasing the exposure (well, perhaps not when you are starting with clipped highlights) and this can bring its own troubles with higher ISO (noise) and longer shutter times (motion blur, camera shake etc). ETTR does also demand a slower process as you take time to adjust the exposure so it is not the solution in all cases.

Camera manufacturers could do more to enable this type of photography. Automatic exposure for highlights/shadows and manual exposure compensation (using the histogram) is not reflected in the RAW editor (at least not in OV3). For example you can see the manual exposure compensation applied in the properties window but when you switch to the editor window it puts the exposure compensation bar at zero. Why not put it at the value you entered (and allow you to alter it up or down) and have an "as shot" or "reset" toggle as in the other types of compensation you can apply (eg Gradation, Sharpness, Contrast).
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  #19  
Old 4th November 2014
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Re: Is this taking Expose To The Right (ETTR) too far?

There's a highly readable article on digital exposure written by Andrew Rodney (aka the Digital Dog) here: http://www.digitalphotopro.com/technique/camera-technique/exposing-for-raw.html#.VFjXP5Vybgs

I commend it to you.
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  #20  
Old 4th November 2014
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Re: Is this taking Expose To The Right (ETTR) too far?

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Originally Posted by bilbo View Post
There's a highly readable article on digital exposure written by Andrew Rodney (aka the Digital Dog) here: http://www.digitalphotopro.com/technique/camera-technique/exposing-for-raw.html#.VFjXP5Vybgs

I commend it to you.
The second paragraph ('What Is RAW Linear Data?') is what Bruce Fraser said in his 'Camera Raw' book I mentioned above. Reading the Andrew Rodney piece, it looks like he was basically requoting Fraser.

(For those that don't know the late Bruce Fraser, he worked closely with Adobe on Photoshop and is in the 'Adobe Hall of Fame'. He is also devised the CMS (Colour Management System) that is the basis of digital colour photography.)

Jim
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  #21  
Old 4th November 2014
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Re: Is this taking Expose To The Right (ETTR) too far?

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Originally Posted by Rawcoll View Post
Hmm, not sure about that. The contrast of the scene itself won't have changed, so I think the contrast is still there, it's just that the histogram has moved up the response curve. But doesn't A/F work at a different aperture to the taking aperture? And the shutter speed shouldn't affect it as focusing is performed with the sensor exposed.

The problem may well be that a black cat with a black background, or a white rabbit in snow, is already a low contrast scene, and so the A/F might well struggle whatever the camera exposure settings. So I don't think the A/F issue is peculiar to this way of working.
I agree that the histogram would have moved up the response curve but as a result there will be less proportionally between the higher values and I guess that's why you get better signal to noise ratio's.

The way I look at this is when you have a contrast detection AF system it gets its signals from the sensor itself. With the EM1 (mirrorless) I assume when you ETTR you turn up the gain on the photo diodes so it must be using the wysiwyg image in order to focus.

I took my EM1 for a walk this afternoon there was very good light and I tried this ETTR method using the histogram display with the limits set at 255 and 0. When I tried to take pictures of aircraft in the sky (SAF), after I wound the ETTR as far as it would go until I saw a clipped highlight then wound it back 1 (I am set to 1/3 stops), I could not get the aeroplane to lock focus at all easily. There was less contrast now in the image. But when I wound the exposure back to zero it easily locked focus.

Now this was not a very scientific test but I tried it several times and I would have to say that I felt it more difficult to get focus locked when ETTR.
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  #22  
Old 4th November 2014
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Re: Is this taking Expose To The Right (ETTR) too far?

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Originally Posted by birdboy View Post
I agree that the histogram would have moved up the response curve but as a result there will be less proportionally between the higher values and I guess that's why you get better signal to noise ratio's.

The way I look at this is when you have a contrast detection AF system it gets its signals from the sensor itself. With the EM1 (mirrorless) I assume when you ETTR you turn up the gain on the photo diodes so it must be using the wysiwyg image in order to focus.

I took my EM1 for a walk this afternoon there was very good light and I tried this ETTR method using the histogram display with the limits set at 255 and 0. When I tried to take pictures of aircraft in the sky (SAF), after I wound the ETTR as far as it would go until I saw a clipped highlight then wound it back 1 (I am set to 1/3 stops), I could not get the aeroplane to lock focus at all easily. There was less contrast now in the image. But when I wound the exposure back to zero it easily locked focus.

Now this was not a very scientific test but I tried it several times and I would have to say that I felt it more difficult to get focus locked when ETTR.
I suppose I was being a bit too simplistic about the contrast not changing, as I guess it will depend on the shape of the response curve of the sensor. Some response curves just keep climbing in a straight line until clipping suddenly occurs (like my GH2 does), in which case I don't think the contrast will change much. Other sensors, like that in the E-M1, have a pronounced S-curve with a roll-off towards clipping, and I can see that there will be a reduction in contrast as the image data is shifted towards the top end. I guess this is what you were finding, but to be honest, I haven't a clue how A/F is exactly implemented. Your take on it makes sense though.
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  #23  
Old 4th November 2014
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Re: Is this taking Expose To The Right (ETTR) too far?

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Originally Posted by Jim Ford View Post
Definitely a big NO!

Half the detail in the image is in the brightest stop. This means that if you underexpose by one stop, you've only captured half the detail available for the image. Underexpose by two stops and you've only captured one-quarter of the detail.

If you then 'spread' the histogram in PP, in order to attempt to get a full tonal range, you run the risk of posterisation.

The late-great Bruce Fraser sums it up well in his 'Real World Camera Raw Adobe Photoshop CS2' book (pages 6-8). It may be old(ish), but like all his books in this series is well worth getting.

Jim
I should also have mentioned that underexposing and subsequently spreading the histogram in PP, will 'pull up' potentially noisy dark tones into the middle ranges, where the noise will be very noticeable.

Jim
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  #24  
Old 4th November 2014
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Re: Is this taking Expose To The Right (ETTR) too far?

Quote:
Originally Posted by birdboy View Post
I agree that the histogram would have moved up the response curve but as a result there will be less proportionally between the higher values and I guess that's why you get better signal to noise ratio's.

The way I look at this is when you have a contrast detection AF system it gets its signals from the sensor itself. With the EM1 (mirrorless) I assume when you ETTR you turn up the gain on the photo diodes so it must be using the wysiwyg image in order to focus.

I took my EM1 for a walk this afternoon there was very good light and I tried this ETTR method using the histogram display with the limits set at 255 and 0. When I tried to take pictures of aircraft in the sky (SAF), after I wound the ETTR as far as it would go until I saw a clipped highlight then wound it back 1 (I am set to 1/3 stops), I could not get the aeroplane to lock focus at all easily. There was less contrast now in the image. But when I wound the exposure back to zero it easily locked focus.

Now this was not a very scientific test but I tried it several times and I would have to say that I felt it more difficult to get focus locked when ETTR.
Hi there Birdboy!

You don't say which lens you were using on the E-M1 - was it a four thirds or a micro four thirds lens, as only the micro four thirds lenses will use contrast af, the four thirds lenses will all use pdaf.

Cheers,

Ralph.
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  #25  
Old 4th November 2014
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Re: Is this taking Expose To The Right (ETTR) too far?

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Originally Posted by Jim Ford View Post
I should also have mentioned that underexposing and subsequently spreading the histogram in PP, will 'pull up' potentially noisy dark tones into the middle ranges, where the noise will be very noticeable.

Jim
And from experience I can say that this can happen even with images of a well-lit landscape shot at ISO 200 with the E-M5.
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  #26  
Old 4th November 2014
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Re: Is this taking Expose To The Right (ETTR) too far?

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Originally Posted by Ralph Harwood View Post
Hi there Birdboy!

You don't say which lens you were using on the E-M1 - was it a four thirds or a micro four thirds lens, as only the micro four thirds lenses will use contrast af, the four thirds lenses will all use pdaf.

Cheers,

Ralph.
Hi Ralph it was a mFT lens the Tamron 14-150mm. I realise that the FT lens use pdaf and am not at all knowledgeable how the pdaf on board sensors behave when you mess with the exposure, but I would guess that the gain is turned up on them also as I would think the whole sensor gain is turned up rather than an individual photosite.
John
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  #27  
Old 4th November 2014
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Re: Is this taking Expose To The Right (ETTR) too far?

Quote:
Originally Posted by birdboy View Post
I agree that the histogram would have moved up the response curve but as a result there will be less proportionally between the higher values and I guess that's why you get better signal to noise ratio's.

The way I look at this is when you have a contrast detection AF system it gets its signals from the sensor itself. With the EM1 (mirrorless) I assume when you ETTR you turn up the gain on the photo diodes so it must be using the wysiwyg image in order to focus.

I took my EM1 for a walk this afternoon there was very good light and I tried this ETTR method using the histogram display with the limits set at 255 and 0. When I tried to take pictures of aircraft in the sky (SAF), after I wound the ETTR as far as it would go until I saw a clipped highlight then wound it back 1 (I am set to 1/3 stops), I could not get the aeroplane to lock focus at all easily. There was less contrast now in the image. But when I wound the exposure back to zero it easily locked focus.

Now this was not a very scientific test but I tried it several times and I would have to say that I felt it more difficult to get focus locked when ETTR.
I seem to recall reading that focussing performance can be improved by shooting in Vivid mode so it should follow that less contrast will impair focussing.
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Old 4th November 2014
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Re: Is this taking Expose To The Right (ETTR) too far?

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I seem to recall reading that focussing performance can be improved by shooting in Vivid mode so it should follow that less contrast will impair focussing.
Good point John. I think we sometime forget the jpeg setting we use and think that they are not important because we shoot in raw. But one of the article referred to in this thread (I think it was bilbo's) reminded me that what you see on the camera viewfinder/lcd is a version of the jpeg using the camera's jpeg settings as you cannot view RAW files they all have to be converted. If you don't believe this with the camera set to raw look through viewfinder or lcd then change your white balance (lever 2 back wheel) and see the colours change yet we know setting the WB can be changed post camera.
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  #29  
Old 16th November 2014
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Re: Is this taking Expose To The Right (ETTR) too far?

I just noticed this thread. An interesting discussion.

I had a quick go this morning with some Swans, and I'm quite impressed with the results (I may just be easily satisfied). Taken in A mode, +1.3 EV, bracketed up by another .7 to 2.0. ESP metering, 800 ISO, 300mm, f6.7 at 1/32, handheld.

There were no blown highlights. I'm certainly going to use this technique for landscapes and see how I get on, I'm not sure about this kind of shot - I should have shot at normal values with ISO 200 for comparison, but I wasn't alone and had to keep up.

Adjusted version (This is cropped to about half the size).

Swans by johndal, on Flickr
100% crop


A crop of the unadjusted version for comparison:


100% crop
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  #30  
Old 16th November 2014
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Re: Is this taking Expose To The Right (ETTR) too far?

That's a good practical example, John.
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