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03-29-2016, 06:36 AM   #1
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ISO Invariance ETTL

I started reading about invariance a few years ago and have played around with ETTL on the K7 (failure) and GR (success). At this point my custom settings are set to expose a stop under and this works very well for me. I have read that with the K5 and moving forward, this practice works well. How many of you are doing this and what are your thoughts? It will be interesting to see how this works in practice with the K1. A general Google search on ISO Invariance will present some interesting articles if you are interested in the topic.

03-29-2016, 06:49 AM   #2
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QuoteOriginally posted by indy Quote
I started reading about invariance a few years ago and have played around with ETTL on the K7 (failure) and GR (success). At this point my custom settings are set to expose a stop under and this works very well for me. I have read that with the K5 and moving forward, this practice works well. How many of you are doing this and what are your thoughts? It will be interesting to see how this works in practice with the K1. A general Google search on ISO Invariance will present some interesting articles if you are interested in the topic.
I usually ETTR to get as much data to work with as I can and reduce noise. But, to each his own.
03-29-2016, 07:01 AM   #3
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Because of the Sony sensors, I don't use ETTR.
This sensors can be light up by several EVs in RAW-development, because of the low noise levels.
I don't use jpg, it may be different there

I'l hope that the K-1 will give even more possibilities there.

Last edited by joergens.mi; 03-29-2016 at 08:28 AM.
03-29-2016, 07:26 AM   #4
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For me on the K-5, it depends on whether I suspect that I'll need post-processing anyway for a given (set of) photograph(s) or not. If so, I do reduce ISO and/or exposure times or both depending on my needs and the subject range of tones - not necessarily to the very left - otherwise I aim at usable JPGs. Usually my post-processing shift is somewhere in between 1.5 and 3, rarely up to 5 EVs.

03-29-2016, 07:28 AM   #5
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The sensors on the k-5 and k-3 produce a lot of noise if underexposed so I use ETTR to get as much clean information as possible. I shoot only RAW though, jpeg might be different.
03-29-2016, 09:08 AM   #6
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It varies with the camera, mode (auto vs manual), and your post-processing routine. I always use raw not JPG.

The K-5 has legendary shadow recovery and low noise. It does less well with highlight recovery. Therefore, I'll often expose to the left when using Av and other semi-auto modes to avoid blown highlights. My K-5 often has -1 stop of exposure compensation dialed in when I'm shooting outdoors, then I boost exposure in Lightroom. In full Manual mode I expose further to the right to reduce noise.

My GR behaves differently than my K-5. The GR isn't quite so good with shadows but gives more leeway for correcting highlights, so I rarely use exposure compensation unless I see an especially tricky lighting situation while in Av or TAv mode.

---------- Post added 03-29-16 at 12:12 PM ----------

QuoteOriginally posted by jatrax Quote
...The sensors on the k-5 and k-3 produce a lot of noise if underexposed...
My experience with the K-5 is different: a little underexposure is often a good way to shoot because lifted shadows don't show much noise. Any camera will produce noise if underexposed too much, though.
03-29-2016, 09:53 AM   #7
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QuoteOriginally posted by indy Quote
I started reading about invariance a few years ago and have played around with ETTL on the K7 (failure) and GR (success). At this point my custom settings are set to expose a stop under and this works very well for me. I have read that with the K5 and moving forward, this practice works well. How many of you are doing this and what are your thoughts? It will be interesting to see how this works in practice with the K1. A general Google search on ISO Invariance will present some interesting articles if you are interested in the topic.
ISO Invariance? ETTL? -1 EC?

OK...I know about the theory of ISO invariance and practice ETTL regularly in my film photography. In that world it is simply called "expose for the shadows" and works best if you know how to use a spot meter and are familiar with compensating development to save the highlights. (The dynamic range of photographic film is far more than the nominal 10-stops of the classic zone system, particularly with the high values.) I sort of get the -1 EC, but that seems like sort of a blunt tool.

From what I can tell, the notion of ETTL coupled with ISO invariance is really not ETTL at all since the intent is NOT to preserve shadow detail, but instead is to reduce noise and retain highlight detail. My understanding of the process?
  • Shoot RAW
  • Shoot at moderate to low ISO
  • Be open to aggressive underexposure while maintaining awareness of low-value (shadow) clipping
  • Adjust brightness in PP to bring the middle and high areas up to their appropriate display values
It is that third point that is the sticky one since clipping in the shadows, as with highlight clipping, is irrecoverable. An unflipped bit is an unflipped bit regardless of ISO setting. I might also add that the above works best when working with fixed ISO in live view with active histograph monitoring. Alternatively you can use a spot meter to determine the dynamic range of the subject and use that to determine where you place your exposure remembering that the camera will clip at zone X, but may have data 2-3 stops below zone I.

For me, the practical approach has been:
  • Shoot RAW
  • Use low to moderate ISO
  • Expose to the right to avoid highlight clipping and maximize total image data
  • Bump or compress (more common) the histogram in PP to bring up the shadows or middle as needed


Steve

Last edited by stevebrot; 03-29-2016 at 10:00 AM.
03-29-2016, 09:59 AM   #8
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regarding this topic about ETTL (not to be confused with E-TTL as a flash feature on Canon/Nikon) which I also touched on in this thread I started earlier on...
https://www.pentaxforums.com/forums/38-photographic-technique/314374-golden-r...lm-days-2.html

When people say they use ETTR, I think it implies that they would push exposure to the right (of the exposure histogram) as much as possible without clipping the brightest spots in a given scenario. A typical example would be in a sunset scene. When spot metering is used, it may be easier to achieve (just point to the brightest spot and lock AE-L). However, it is not so easy in center-weight or matrix metering as it may lead to highlights being clipped and non-recoverable details. I have owned k-7 before, and now k-5, k-3 (Sony sensors), my usual practice now is setting EV to -0.3 (to start with and then chimp from there if necessary); I couldn't do that with my k-7 as it would introduce noise when it is underexposed.

My reasoning for leaning toward ETTL is because the sensor technology (i.e. dynamic range) in the latest Sony sensors has provided cushion for underexposure errors without much noise penalty. A friend of mine who is a Canon user, said he can not do that, because of the noise introduced in underexposed photos. So my practice is to ETTR without clipping highlights, but I would prefer to err on ETTL if I have to choose in some situations.


Last edited by aleonx3; 03-29-2016 at 10:53 AM.
03-29-2016, 10:17 AM   #9
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QuoteOriginally posted by DeadJohn Quote
lifted shadows don't show much noise.
Lifted shadows do show more noise that non-lifted. Which is why I use ETTR. Which brightens the shadows in camera and allows more data to be recorded. Of course blown highlights are worse than a little noise so ETTR (for me) means exposing as far right as possible without clipping the highlights. That is the best exposure you can get with a digital image. You can then pull back the highlights a bit if needed, and still raise shadows to increase the total dynamic range, but the noise is far less. I try to expose so that anything pure white, a bright cloud for example, just barely starts to clip in spots. Sort of using the old zone system, if it is pure white, expose so that it actually is pure white. Then let everything else fall where it can.

But there are lots of ways to get the job done, use whatever works.

---------- Post added 03-29-16 at 10:19 AM ----------

QuoteOriginally posted by aleonx3 Quote
So my practice is to ETTR without clipping highlights, but if I would prefer to err on ETTL if I have to choose in some situations.
Probably correct. Depending on the situation. ETTR provides the least noise but if doing so clips the highlights then it is not worth it. That would actually be ETFTTR. (Expose too far to the right)
03-29-2016, 01:29 PM   #10
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These discussions are always funny because people who shoot very different things talk past each other. Whenever ETTR, ETTL is discussed one should describe what type of photography is referred to.

I always (close to anyway) shoot pictures with sky and ground and at decent light levels. My biggest problem is blown highlights in the sky as I want details across the frame. Exposing for the shadows would lead to blown highlights everywhere. An auto exposure mode that exposed to the right (the RAW right that is) and allowed to set a maximum amount of highlight clipping would be great.
03-29-2016, 02:04 PM   #11
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QuoteOriginally posted by house Quote
An auto exposure mode that exposed to the right (the RAW right that is) and allowed to set a maximum amount of highlight clipping would be great.
Yes. Having just bought into C**** to be able to use MPE65, it maybe considered heresy by some diehards for me to point out that Magic Lantern, the open source firmware developed for C**** cameras, has this feature. I loaded Magic Lantern onto a DSLR last night and this was one of the things I noticed.
03-29-2016, 03:41 PM   #12
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QuoteOriginally posted by Nass Quote
Yes. Having just bought into C**** to be able to use MPE65, it maybe considered heresy by some diehards for me to point out that Magic Lantern, the open source firmware developed for C**** cameras, has this feature. I loaded Magic Lantern onto a DSLR last night and this was one of the things I noticed.
It won't be to the RAW right, Nass, unfortunately it will be to the JPEG right.

The highlight blinky in Live View in our cameras is accurate, though, as I understand it.
03-29-2016, 07:01 PM   #13
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QuoteOriginally posted by stevebrot Quote
ISO Invariance? ETTL? -1 EC?

OK...I know about the theory of ISO invariance and practice ETTL regularly in my film photography. In that world it is simply called "expose for the shadows" and works best if you know how to use a spot meter and are familiar with compensating development to save the highlights. (The dynamic range of photographic film is far more than the nominal 10-stops of the classic zone system, particularly with the high values.) I sort of get the -1 EC, but that seems like sort of a blunt tool.

From what I can tell, the notion of ETTL coupled with ISO invariance is really not ETTL at all since the intent is NOT to preserve shadow detail, but instead is to reduce noise and retain highlight detail. My understanding of the process?
  • Shoot RAW
  • Shoot at moderate to low ISO
  • Be open to aggressive underexposure while maintaining awareness of low-value (shadow) clipping
  • Adjust brightness in PP to bring the middle and high areas up to their appropriate display values
It is that third point that is the sticky one since clipping in the shadows, as with highlight clipping, is irrecoverable. An unflipped bit is an unflipped bit regardless of ISO setting. I might also add that the above works best when working with fixed ISO in live view with active histograph monitoring. Alternatively you can use a spot meter to determine the dynamic range of the subject and use that to determine where you place your exposure remembering that the camera will clip at zone X, but may have data 2-3 stops below zone I.

For me, the practical approach has been:
  • Shoot RAW
  • Use low to moderate ISO
  • Expose to the right to avoid highlight clipping and maximize total image data
  • Bump or compress (more common) the histogram in PP to bring up the shadows or middle as needed


Steve
Thanks for this post. Yes two concepts wrapped up in the title.

I shoot raw and ETTL which in turn pushes the iso down. With the GR I have set the user settings for -.3 (not -1... typo).

I suppose this would be blunt if I shot this way all the time, but these settings are for snap focus quick shots to avoid blowing highlights. If I have time to compose I adjust the exposure as appropriate to avoid blowing highlights which more often than not results in ETTL.

As I understand invariance you could shoot the K5/GR at iso 800 properly exposed or at iso 100 and pp to the proper exposure and end up with two images with similar noise. With some sensors this invariance exists from iso 100-1600. So in theory you don't have to be that concerned with ISO?

If I can shoot any iso in a given range and get the same noise level in pp, it makes agressive protection of highlights easier. It also makes TAv + ETTL a nice starting point for keeping iso down and preserving said highlights by pushing shadows.
03-29-2016, 09:52 PM   #14
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QuoteOriginally posted by stevebrot Quote
.

From what I can tell, the notion of ETTL coupled with ISO invariance is really not ETTL at all since the intent is NOT to preserve shadow detail, but instead is to reduce noise and retain highlight detail.

Steve
I also think it has nothing to do with ETTL. Ideally you shoot at lowest iso and ETTR, and if you are concerned about blowing highlights you reduce exposure some. But (and this is the point) if you are limited in exposure by f-stop and shutter speed, then instead of increasing iso, take the shot at lowest iso. The noise and DR will be no worse (on the K-5 anyway, and almost the case with K-x) and you will have more protection from overexposing highlights.
03-30-2016, 06:42 AM   #15
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To me "correct" exposure is not so much a technique as an art.
I always shoot RAW and ETTR. But as a practical matter I often don't hesitate to burn a few pixels.
Depending on the circumstance, which for my wild bird shots, I hardly ever have any control over, slight over-exposure often gives me finer shadow detail and more overall-pop then a conventional ETTR shot. You have to interpret the overall scene a bit.

Taken yesterday with a Q at 560mm and slightly over exposed.

Last edited by wildman; 04-02-2016 at 04:20 PM.
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