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Author Topic: Expose to right, it is as simple as  (Read 31906 times)
feppe
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« Reply #20 on: July 31, 2011, 07:17:17 PM »
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I have the impression that Michael suggested a setting for ETTR. Would we have a setting for ETTR we would not really need to care about blown out highlights, because the camera would never overexpose non specular highlights.

There are some practical issues with automating ETTR exposure. To start with I would like to have histogram calculated from RAW pre color balance.

Olympus has ETTR in some (all?) of their FT/MFT cameras, perhaps compacts. Guillermo Luijk posts some reservations about its utility later in the thread.
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bjanes
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« Reply #21 on: July 31, 2011, 07:41:07 PM »
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What if you are shooting handheld in low light, does ETTR still make sense? Does ETTR only make sense at the lowest possible ISO setting? Should one trade ISO for speed in order to ETTR when conditions require it?

I regularly shoot handheld very low dynamic range scene in low light where all the data falls within one stop.  There are now essentially 4 variables in play to achieve an acceptable exposure: timing, aperture, ISO, and 'amount of ETTR'.

For instance, here are few possible exposure choices at a given aperture:

ISO 400 1/200 no-ETTR
ISO 1600 1/200 max-ETTR
ISO 400 1/50 max-ETTR
ISO 100 1/50 no-ETTR

Which is best?

That depends on the read noise of the sensor and the camera electronics. For a detailed discussion, see Emil Martinec. For older cameras such as the Nikon D3, read noise improves until about ISO 800. Beyond that point, one can leave the camera at ISO 800 and increase exposure in the raw converter. For newer cameras such as the Nikon D7000 and the Pentax equivalent, the results would be very similar regardless of the ISO as long as total exposure is the same. Raising the ISO does limit highlight headroom. With the D7000 you could leave the ISO at base and give as much exposure as f/stop and shutter speed considerations allow, and make up the rest in the raw converter.

The above discussion assumes that total exposure is the same (EV value determined by the f/stop and shutter speed). You don't give the aperture, but I assume that it is the same in the first and last two comparisons.

Regards,

Bill
« Last Edit: July 31, 2011, 07:51:38 PM by bjanes » Logged
madmanchan
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« Reply #22 on: July 31, 2011, 07:41:41 PM »
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Camera profiles in ACR/LR with lightness-dependent color should not have issues with ETTR, as long as you perform the "normalization" using the Exposure slider, rather than the Brightness slider. For example, if I expose an extra 1.5 stops in the field (relative to how bright I want the actual image to be), then in ACR I would compensate with Exposure -1.5.

Eric
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John Camp
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« Reply #23 on: July 31, 2011, 08:16:09 PM »
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It seems to me that Michael is giving us the recipe for a metaphorical pie, while the engineers are telling us how to make flour and grow cherries. If I want to make a pie, I need a recipe, not a treatise on milling. I think Michael made the recipe pretty understandable, and it allows me to function better as a photographer. Throwing a lot of engineering stuff at me does not, because not only do I not understand it, I don't really care to. That's what engineers are for. No offense.

JC
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David Sutton
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« Reply #24 on: July 31, 2011, 08:26:30 PM »
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+1 (also no offence to the engineers Smiley)
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Sekoya
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« Reply #25 on: July 31, 2011, 08:52:04 PM »
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It always amazes / annoys / amuses me when I publish an article that has been painstaking peer-reviewed by some of the brightest minds in the industry – people who design sensors and write raw software (in this instances) and then "experts" whose credentials are unknown tell me (us) why the information in the article is wrong.

This was the case with my original ETTR article. I think I trust Thomas Knoll's knowledge of digital imaging (the original author of Photoshop and Camera Raw) over some online commentator.

Similarly in this instances. I'm sure that there are areas to quibble over (both scientists and artists love to quibble). But when it comes to arcania and subtleties in complex topics I'll continue to trust known experts whose bona fides are well established.
Michael, your article might be absolutely correct but that does not mean that are not additional aspects that can be legitimately discussed. And whenever one tries to simplify things to some extent (which you tried in your article), there can be a legitimate discussion as which aspects got not discussed in full because the simplification omitted them.
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Sekoya
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« Reply #26 on: July 31, 2011, 08:54:49 PM »
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I don't see why we won't have raw based histograms. As far as I can recall the Leica S2 has raw based histograms but most other cameras have histograms calculated from JPEG. >Don't know why!
We already have UniWB but that still is influenced by JPEG tone curve (even if we try to make that as neutral as possible).
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michael
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« Reply #27 on: July 31, 2011, 08:58:27 PM »
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Michael, your article might be absolutely correct but that does not mean that are not additional aspects that can be legitimately discussed. And whenever one tries to simplify things to some extent (which you tried in your article), there can be a legitimate discussion as which aspects got not discussed in full because the simplification omitted them.

I have no problem with additional legitimate discussion. My concern is that people without in-depth technical knowledge and expertise simply get confused, and thus turned off when the discussions becomes too arcane.

Michael
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FranciscoDisilvestro
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« Reply #28 on: July 31, 2011, 09:13:45 PM »
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Just wanted to share some experiences with ETTR and RAW converters. Some of them do not expect images to be taken this way, or at least I have not been able to obtain satisfactory results, at least with programs like Nik Capture NX or DXO Optics Pro (both give very good results with normally exposed pictures and DXO is really good with underexposed pictures). The main issue I get is that even if I can adjust exposure, the image is very dull.

On the other hand, LR/ACR handle ETTR images really well, resulting in vibrant images.

One interesting program I´m testing now is Raw Therapee, which probably is still in an experimental state, but it has a section of RAW preprocessing, that I haven´t seen anywhere else, where you can perform the "normalization" (besides other advanced techniques) before post processing.

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Schewe
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« Reply #29 on: July 31, 2011, 10:51:13 PM »
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The amount of recovery in your Niagra Falls shot is astounding, but the raw file is not nearly so clipped as the ACR histogram would suggest, likely because of the BaselineOffset that ACR uses for your camera.

Which is the point I was trying to make...even when an image seems pinned to the highlights with numeric indications of clipping, a lot of that data is simply clumped up in the highlights and can be utilized...guess what the back of the camera on that image looked like? Yep, completely white...but there was a surprising amount of usable detail remaining. Which more than anything proves that exposing to the right isn't nearly as likely to clip highlights if done carefully. And actually, I've been playing with an unannounced raw converter that does even better with the highlights, sorry, can't talk about it :~)
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Michael Sullivan
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« Reply #30 on: July 31, 2011, 11:20:58 PM »
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Essentially, ETTR is the digital complement to the Exposure component of Ansel Adams' Zone System -- capture as much information as possible in the exposure, with the intention of working with that information in later stages to create an image.  It is accomplished differently in digital than in film, i.e., expose to the right instead of expose for the shadows, but the objective is the same. 

Understandably, automatic metered film cameras never incorporated this concept, because the expectation was that most users would simply opt for straight processing and printing.  Likewise, for digital cameras, the designers' assumption for automatic modes is that the camera should capture an image that is as close as possible to a printable image, which gives up the benefits of having an initial image recorded that includes as much information as possible for later redistribution.  Camera makers are unlikely to design their cameras to overexpose without clipping by default, because such images will look terrible if they are simply printed or pulled into iPhoto or Picasa.  Unless there is a exposure-boost tag that automatically causes the standard photo programs to crank down the exposure by the same amount, pictures will look without manipulation.

Perhaps a more useful approach would be to use ETTR metering techniques when recording RAW images, on the assumption that anyone using RAW will be processing images individually and will be positioned to take advantage of the improved data capture.
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Nick Rains
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« Reply #31 on: July 31, 2011, 11:25:12 PM »
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Hi!

I don't see why we won't have raw based histograms. As far as I can recall the Leica S2 has raw based histograms but most other cameras have histograms calculated from JPEG. >Don't know why!

Best regards
Erik

Hi Erik

The rumour about S2 raw histograms is incorrect. It is the same as any other camera. I am at the Leica factory this week with access to the technical people. This is a question I want to raise.
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Nick Rains
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« Reply #32 on: July 31, 2011, 11:34:19 PM »
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And actually, I've been playing with an unannounced raw converter that does even better with the highlights, sorry, can't talk about it :~)

This will be interesting to hear more about when you are able to discuss it.

Highlight recovery is hugely important for all the reasons discussed above. Currently, and I'm a big LR3 user/fan, Aperture seems to do the best job at recovering highlights. You can even work with a histogram which actually shows the 'clipped' data ie the data to the right of the 255 point. I have not measured per se, it but I can definitely get better quality highlight recovery and about 0.5 stops more exposure before total blowout compared to LR3. Extra exposure reduces shadow noise, this much is quite clear.
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Nick Rains
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kwalsh
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« Reply #33 on: July 31, 2011, 11:35:09 PM »
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I have no problem with additional legitimate discussion. My concern is that people without in-depth technical knowledge and expertise simply get confused, and thus turned off when the discussions becomes too arcane.

Michael

Hi Michael,

I agree completely, and that's why I put my comment on quantization noise vs. read and shot noise only in a P.P.S. about something I thought more relevant (color errors from RAW converters with ETTR) - I think the "levels" argument while not strictly correct is probably a lot easier for most people to understand and nearly functionally equivalent.  If the comment wasn't welcome here, my apologies.

Ken
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ErikKaffehr
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« Reply #34 on: July 31, 2011, 11:54:35 PM »
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Nick,

Enjoy your time in Germany and also meeting with the Leica people!

Best regards
Erik


Hi Erik

The rumour about S2 raw histograms is incorrect. It is the same as any other camera. I am at the Leica factory this week with access to the technical people. This is a question I want to raise.
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Mcarthur
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« Reply #35 on: August 01, 2011, 02:23:47 AM »
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Could someone please explain what happens in the post-processing once the exposure has been "corrected" for darker scenes?
Since major correction is only needed for dark scenes, ignore the near-white, minor correction scenario.

If I save the file as jpeg, aren't I simply throwing out all that good work? Is it pretty much the same as if I had taken jpeg only in-camera (pls ignore any other raw processing effects and assume I'm using the manufacturers converter which applies identical raw->jpeg as in-camera)?

If I save it as 16bit non-raw, say tiff, will the move from 14bit camera -> (I presume) 32 bit lightroom -> 16 bit file throw out any benefit? 

I presume that saving to 32 bits won't have any effect (will it?).

Thanks!
PS. I can understand pretty detailed maths, so go to it if you need to
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Anders_HK
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« Reply #36 on: August 01, 2011, 04:22:51 AM »
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Essentially, ETTR is the digital complement to the Exposure component of Ansel Adams' Zone System -- capture as much information as possible in the exposure, with the intention of working with that information in later stages to create an image.  It is accomplished differently in digital than in film, i.e., expose to the right instead of expose for the shadows, but the objective is the same.  
ge of the improved data capture.

EXACTLY. When viewed this way it is amazing how much is same or parallel to what Ansel wrote in his book The Negative! There is also the book by Chris Johnson "The Practical Zone System" which contain perhaps the best chapter yet written on how the zone system applies to digital capture.

Michael's article discusses solely automatic metering based on ETTR, but is there not also a manual approach of using the Zone system at arriving at an optimized exposure (one shot) at RAW (ETTR)? I would argue that there is on basis of a single spot meter for the brightest highlight in a scene, on basis of knowing how many stops above neutral that occurs for the sensor being used and manually setting exposure for a camera or digital back accordingly. Add to that the ability to visualize Zones I, II, VIII and IX and perhaps Zone V middle tone, and there it is, precisely what Ansel Adams did but applied to digital, except he did so for all zones in order to visualize the image at capture. With digital we can slide the other zones around Smiley.

Thus the only difference to Ansel seems that above is applied to a different media; digital. Ansel applied to B&W film and more in his days but not digital. Thus… not all exposure metering have changed per say but perhaps some have been forgotten? Above is perhaps a manual means of an addition to Michael’s article?  Grin

Thereby the basic fundamentals of metering remains the same as they always have... ; with adoption to the media of capture, just like Ansel Adams. For automatic exposure, Michael seem precise right.

Regards
Anders
« Last Edit: August 01, 2011, 07:35:48 AM by Anders_HK » Logged
stamper
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« Reply #37 on: August 01, 2011, 04:39:18 AM »
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Camera profiles in ACR/LR with lightness-dependent color should not have issues with ETTR, as long as you perform the "normalization" using the Exposure slider, rather than the Brightness slider. For example, if I expose an extra 1.5 stops in the field (relative to how bright I want the actual image to be), then in ACR I would compensate with Exposure -1.5.

Eric

The default setting in ACR isn't linear. There is a contrast boost. If what you state is desirable then the settings should be zeroed out? Adobe should zero the settings as a starting point rather than a contrast boost. At lot of users don't know about this.
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stamper
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« Reply #38 on: August 01, 2011, 04:55:16 AM »
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I thought I understood the ETTR method of exposure and exposure in general but the article has me thinking again.

Quote

In the case of the white cat and snow – yes – you would do the same as for film – increase the exposure so that it looked correct. But in the case of the black cat on the coal pile you would do the opposite of what you would do for film. Instead of decreasing the exposure to make the cat and coal look black, you would increase the exposure the same as you would for the white cat and the snow.

Unquote

Does this mean that every image I take I should have my EV set at plus 1.0 ( or similar ) regardless of the brightness - or lack of it - in a scene and if it is looking pushed to the right in ACR  - without it being overexposed - and then simply reducing the exposure till the histogram has an even distribution of data? Up until now I have been using the Digital Zone method with success but I am now wondering about the method being discussed. BTW this whole thread and article is very worthwhile and if someone manages to counter what Michael has stated then it is still informative. Smiley
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chrisreay
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« Reply #39 on: August 01, 2011, 05:11:17 AM »
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Does this discussion apply to the electronic viewfinder cameras? I had assumed that the exposure was assessed from the actual sensor data and might be a more accurate reflection of the sensor's capabilities.
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