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03-10-2016, 10:14 AM   #1
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Focus Peaking and Highlight Alert

Hi everyone,

I discovered something rather funny: Focus Peaking tends to make highlight alert oversensitive.

Here are two (artistically brilliant ) pictures taken in exactly identical situations (and in focus) to illustrate the effect:
  • In the firs picture, focus peaking is turned off: no sign of overexposure
  • In the second picture, focus peaking is activated highlight exposure is visible
It is funny, but it makes focus peaking harder to use, imo. I suspect highlight alert to be applied on the displayed image AFTHER focus peaking. And since focus peaking turns the in focus area white, those area are overexposed.

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03-10-2016, 10:57 AM - 1 Like   #2
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I'm following you. Good observation -thx for sharing
03-10-2016, 11:22 AM   #3
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I think your observation and explanation are right.

I do seem to recall that when focus peaking was first introduced, there was criticism that the histogram was based on what came out of the display, rather than what was hitting the sensor. I think that was in a review of either the K-01 or the K-30, I can't remember.
03-10-2016, 11:40 AM   #4
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QuoteOriginally posted by Tanzer Quote
I think your observation and explanation are right.

I do seem to recall that when focus peaking was first introduced, there was criticism that the histogram was based on what came out of the display, rather than what was hitting the sensor. I think that was in a review of either the K-01 or the K-30, I can't remember.
Then let's hope for a firmware update? 😃

I suspect that what you say is still the case. I did a quick test and the histogram displayed in Live View matches the histogram of the picture relatively well. However, that (those) histogram is the histogram of the embedded jpeg, and NOT of the RAW. And that embedded jpeg is dependent of the development setting, particularly the contrast...

03-10-2016, 01:29 PM   #5
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Good diagnosis of a design quirk. I guess you can work around it by focusing first and turning off peaking before setting final exposure, but that still doesn't solve the fact that the histogram works off the embedded jpg even when using raw DNG mode.
03-10-2016, 01:37 PM   #6
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QuoteOriginally posted by DeadJohn Quote
Good diagnosis of a design quirk. I guess you can work around it by focusing first and turning off peaking before setting final exposure, but that still doesn't solve the fact that the histogram works off the embedded jpg even when using raw DNG mode.
I think I will try to disable highlight exposure and rely on the histogram. A little bit of clipping is not a problem and metering works fine, nowadays. I will also set the contrast to minimum, since I shoot raw.
03-10-2016, 10:46 PM   #7
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In the example you show a small difference may be at work. If a 1/10 e.v. could cause the borderline case to show overexposure it is real but probably only of academic interest. So my question is--do you see a significant difference (e.g., maybe a 1/3 or 1/2 e.v. difference)?
03-11-2016, 01:04 AM   #8
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QuoteOriginally posted by dms Quote
In the example you show a small difference may be at work. If a 1/10 e.v. could cause the borderline case to show overexposure it is real but probably only of academic interest. So my question is--do you see a significant difference (e.g., maybe a 1/3 or 1/2 e.v. difference)?
No, I dont think it's a borderline case. I noticed this longtime ago, when I first used FP, I thought it was that red stuff. Then I wondered what was Highlight Alert... So I was a little confused :/ So I played with both settings because Highlight Alert almost always turns on when focus peaking is activated.

So I have two solutions in mind:
  • Disabling Highlight Alert and expose corectly. Some higlights are not a problem ;-)
  • Keeping Highlight Alert and use it as a more visible FocusPeaking indicator #HackinTheSystem


03-28-2016, 02:50 AM   #9
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I found another strange thing:

While scanning slides with a high dynamic, I tried to expose to the right as much as possible without clipping the highlights. When Focus Peaking is disabled, I found the (live) histogram rather correct in regard with highlights. The red areas in Live View are indeed overexposed in the RAW file.

On the other hand, the histogram of the embedded JPEG displays way more overexposed areas than in Live View. (nb: my contrast settings are set the the minimal value)

I don't fully understand what is going on, but it's interesting to know that you can trust the LV histogram more than the out of camera jpeg.


But here is something even weirder:

I wanted to know the shortest shutter time where whites were never clipped, so I took pictures of pure white (without any slide, only the backlight). I found that 1.6s was the limit: beyond that point, whits might be overexposed. At 1.6s and lower, I'd never be in trouble.

But when I looked at the white surface in Live View, I could never overexpose the image, even with shutter speeds way above 2s. In this situation, I could NOT trust the Live View histogram.


So what are my conclusions?
  • In Live View, the processor does quite a good job in assessing the scene's exposure. I suppose it uses the higher section of the sensors dynamics to evaluate the scene's brightness. This works, even with a rather highly compressed video flux.
  • Don't trust the jpeg
  • What about the pure white? I don't really know :/
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