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Expose To The Right (ETTR)
  • I kept learning more about highlight roll-off, greyscale chart, histogram to make more "film" look when using DSLR. Why?

    These articles give us glimpse into one dark area of DSLR revolution. Our latest and greatest DSLRs still use 100+ years old exposure technology that used to work well with film gadgets. But "CCD and CMOS chips are linear devices." That inherent characteristic of digital sensors doesn't work nicely with the traditional exposure technology that the camera makers are still implementing. Interestingly this might explain why overblown highlight area could suck up most of encoding bits from GH2. The film modes like Smooth and Nostalgic with smooth highlight roll-off seem blessing.

    http://www.luminous-landscape.com/tutorials/expose-right.shtml
    http://www.luminous-landscape.com/tutorials/optimizing_exposure.shtml

  • 55 Replies sorted by
  • @stonebat

    Thanks for posting, but we won't allow topic cosisting with just links to other sites.
  • Just added some introduction.
  • And if someone wants to offer a Cliff's Notes version of those articles, I'd be eternally grateful.

    Here's for staying on V's site.

  • I'm no expert in this area. After googling some terms, it was fun reading.
  • Maybe ask Panasonic to include ETTR menu option in their GH2 firmware update. Then you can save as a Custom on mode dial. :-)
  • I think the basic idea of what he's saying is easy to get and right on. That is that all digital video has underlying noise but you only see it in dark areas because there isn't enough data to not see it. i.e.- light allows more data to be recorded on your sensor/card so you see that and not the noise. So it's better to overexpose and print down than to under expose and bring up the smaller recording of data amongst all the noise.

    Get more data recorded = expose to the right
  • More light = more data. Agreed.

    But, given an inflexible shutter, 1/50. There's only 3 options to increase data, more light, wider aperture or higher sensitivity. In many situations we might already be on the limit of how wide we can open the aperture, or light we can throw on the scene. So how to expose to the right then? Increase sensitivity, or ISO, as most of us call it.

    So the question here is, and I don't have the answer, is it better to ETTR and increase noise, or expose to as close to your intended levels and keep the noise down?
  • I don't think the article covers the low light case. ETTR seems more useful in normal lighting case where u have a choice of ETTR.
  • This seems more useful in photo where we got more wiggle room for high ISO.
  • @itimjim Nothing is free. ETTR works because of the linear nature of the sensor. When you increase the ISO of a digital sensor you are not really increasing the ISO, you are increasing electrical gain. Increasing the gain = lowering the dynamic range. I am not sure of the source at this point (Red Center podcast perhaps) but apparently gain that gives you an extra stop of light will take from you an extra stop of the dynamic range. Low dynamic range = no advantage of the ETTR. ETTR will work only through the variation of the shutter and aperture speed all else being equal. ETTR is a good technique to employ if the post-production color grading is intended.
    Regarding the 1/50 of a second: one can argue that while the 180 degree shutter is the cinematic standard, it might be OK for the low light scenes that are intended to read as a low light scene (and not because you did not have good light) to go as low as Shutter Speed = Frame rate. We, as humans have a natural smearing of the vision in a low light environment (in addition to the wide open pupil) so it would feel natural to have a bit more motion blur in such scenes as opposed to the daylight scenes.
  • It has been applied even in Hollywood movies, like "Collateral". They shot most of the wide night exteriors with 1/25th exposure.
  • @stonebat
    Luminous Landscape's characterization of today's image recording technology as "19th Century" is a valid criticism, but it really only scratches the surface. While a Live View camera could automatically normalize the exposure of each entire frame, that would also be a compromise. What the camera should do is normalize the exposure for each individual macroblock in the image, in order to make optimal use of the digital coding range in each case. To make this approach work properly, the camera would also need to record a low bitrate metadata stream indicating the normalization factor used in each macroblock. Naturally, this would require modifications to existing JPEG and AVCHD codecs, which are long overdue for other reasons as well.
  • ...the camera would also need to record a low bitrate metadata stream indicating the normalization factor used in each macroblock. Naturally, this would require modifications to existing JPEG and AVCHD codecs, which are long overdue for other reasons as well...
    Yes indeed. You know what also would be simply amazing? Simple exif info in the existing setup. How complicated is it for Panasonic to include ISO, f-stop and a shutter info with a video file? As far as I can tell it is not available even with in-camera playback on GH2.
  • The 2011 article says "Now, just to be sure that there is no misunderstanding – this approach only applies to raw files, not in-camera JPGs."
    Doesn't that mean it won't apply to video either?
  • @dkitsov Just because we see more motion blur in low light as a human it does not mean it is more natural for cinema. For example our DOF is huge and we see in stereo, the complete opposite from what would be typically considered cinematic.
  • @soapey It works fine for jpegs, as ETTR is not about recording format but about the way the sensor works.
    @Ptchaw Human eye depth of field in the dark is hardly "huge". While it's true that in the bright day light human eye is roughly @ f/8.3; in the dark room it can be @ f/2.1 (or according to the later research @ f/3.2) wich is still rather below the traditional cinematic f/4 (lower f numbers in the lenses and super shallow dof are recent development in cinema, as a matter of fact super shallow DOF is still only possible with 5D II due to its extra large (from the cinema POV) sensor). The perception of very deep DOF in humans comes from human's ability to reframe and refocus very quickly plus the function of "RAM" our visual system has.
  • @LPowell Wow. That sounds so futuristic!!! I like it for photo, but I'm not sure about video.
  • @dkitsov Are you serious? 35mm is not a new development, shallow DOF has been around for decades, through large format film. Our DOF is huge compared to 35mm film, not just because of perception, but because our retina is comparatively much smaller. As before, just because that's how we see things, it does not mean it's more cinematic.
  • @ Ptchaw Canon 5D mark II: sensor size 36x24mm
    Super35 (most common film format in motion pictures): roughly 22x19mm, full size never used. Difference in area roughly x3.5 times.
    Yes, wide use of "Full" size sensor for video production is a recent development.
    f-number: focal length/aperture diameter(pupil opening diameter)
    Super35 image area (as used for 2.35 projection) = 240mm squared
    Average human eye image sensing area (fixed gaze) = roughly 254mm squared
    DOF a function of image area , focal length, aperture, resolution and the "circle of confusion"). The perception of very deep DOF in humans comes from human's ability to reframe and refocus very quickly plus the function of "RAM" our visual system has. Please make your calculations before making wild claims.
    I will respond to no further flame-bait from you.
  • Thanks for posting these wonderful articles.

    http://www.luminous-landscape.com/tutorials/optimizing_exposure.shtml

    So 32 steps in the darkest areas of the frame explains well why se see so much mud and macro-blocking in these areas, especially on lower bitrate recordings.

    I'm done shooting in dimly lit conditions. I want to shoot 100 iso wherever possible, as the results speak for themselves - lights are the key (pun intended), and yes, I will start to expose to the right and adjust in post! Thankyou.
  • @dkitsov It's not just about sensor size; our eyes have very wide lenses and are pretty slow - even in a very dark room, wide open, they're about f/3.5. In daylight they can be as slow as f/14.9, apparently. At anything other than close focus, you're hardly going to get any bokeh.

    As for film formats, you know about 70mm, right? It is not flame bait, mere fact stating. Obviously you are incapable of interpretting it as such.

    I give you my point again: Just because that's how we see things, it does not mean it's more cinematic.
  • @LucasAdamson Try if you can raise EV at low ISO in good lighting outdoor. I've been trying... but the weather has been suck...
  • Actually I've been researching this, and expose to the right is actually not as great as is being said here. The effective difference is equal to lowering the ISO in all situation, EXCEPT where the ISO will go no lower. This has been demonstrated with some tests I've seen online, in a reply to the luminous landscape article, and it makes a lot of sense to me.

    At ISO 100, if you feel the need for reduced noise (surely pretty pointless really) then by all means ETTR, for all other situations, simply reduce the ISO for an equal or better result than ETTR offers.

    The article:

    http://chromasoft.blogspot.com/2009/09/why-expose-to-right-is-just-plain-wrong.html

    Tell me this guy's wrong, 'cause if he is, I can't see it.
  • His conclusions:
    There is no advantage to image quality from ETTR that can't be duplicated by selecting a lower ISO, if a lower ISO setting is available. In some situations, such as where there is in-camera noise reduction, ETTR actually increases noise. That's what the practical tests show, and the theory of the case confirms the practical results to be correct.
    The only situation where there is an advantage to ETTR is if you're already at the lowest ISO setting your camera, and you use ETTR to synthesize a lower ISO. However, given the noise performance of most modern cameras, that advantage is often very small. The test I did here - a small sensor high pixel count camera - is the best possible scenario for seeing an improvement. Using a modern DSLR, the improvement would be marginal at best.
    Any kind of ETTR brings significant disadvantages in the shape of color and tone curve shifts that will have to be repaired in post processing. While these shifts are small, they are easily the equivalent in effect of changing profiles. So, in effect, ETTR negates the advantages that modern raw developers such as Lightroom bring with them.
    Bottom line - ETTR offers improved image quality in only one specific situation - where you can use a lower ISO setting than your camera has. In all other situations, ETTR will only ever decrease image quality.
  • @LucasAdamson

    These conclusions may be correct regarding noise. But the purpose of ETTR is to maximize luminance/color resolution, not minimize noise. I think you're confusing two image quality issues here.

    [edit]

    Just scanned the article. The author simply doesn't understand the issue. He seems to think that ETTR is exclusively about noise. His tests only involve shooting flat panel color cards, with no gradations.

    I submitted this comment to his blog:

    You're confusing noise performance with luminance/color resolution. "Expose-to-the-Right" (ETTR) is meant to enhance the latter, not the former.

    If you want to test ETTR you need to have color or luminance gradations in your shot, not flat panels. The improvement will EASILY be evident then.