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12-12-2015, 10:17 AM   #1
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Pentax K5 at ISO 80 produces unnatural looking highlights

Hi. I'm new to this forum.

I recently bought a Pentax K5. Reading online about the extended ISO range, I shot a couple of days at ISO 80. I was under the impression that extended ISO 80 provided maximum image quality, but there was something unnatural about the images, especially the highlights. Its hard to explain this but you can get the same effect by pulling the highlights of a slightly overexposed image in raw software.

After reading some more online, it seems extended ISO is basically software pulling or pushing the histogram. Lets say if you shoot at ISO 80, the camera shoots at ISO 100, overexposing by 0.3 EV but pulls the highlights to the left with software (this explains the slightly more dynamic range than ISO100) and if you shoot at ISO 51200, the camera shoots at ISO 12,800 and pushes the exposure with software by two stops - this is the same as shooting at ISO 12,800 and boosting the exposure by 2 stops in raw software.

I know this is a topic discussed many times, but I just wanted to see if anyone else has felt Pentax K5 at ISO 80 produced unnatural looking results especially in the highlights - I could call it compressed highlights look.

12-12-2015, 10:25 AM - 1 Like   #2
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It always amazes me that people make these kinds of posts without sharing any of the offending images.
12-12-2015, 10:30 AM - 1 Like   #3
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Thanks for sharing.

As Edgar says, it is useless to post something like this without an image to help it out. I have used iso 80 many times and it works quite well with pretty amazing dynamic range. For what it is worth, DXO Mark measures the base iso of the K5 at iso 70 and the dynamic range has a definite increase from iso 100 to iso 80 (14.1 vs 13.7 EV).

12-12-2015, 10:46 AM   #4
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Yes, the idea is to save the highlights from clipping, which allows you more latitude in your processing.

12-12-2015, 11:07 AM   #5
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QuoteQuote:
I recently bought a Pentax K5. Reading online about the extended ISO range, I shot a couple of days at ISO 80. I was under the impression that extended ISO 80 provided maximum image quality, but there was something unnatural about the images, especially the highlights. Its hard to explain this but you can get the same effect by pulling the highlights of a slightly overexposed image in raw software.
The trick with the K-5 is expose to the left. It's much more forgiving of under-exposed shadows than it is of blown out high lights. Given a choice, keep the right hand of the histogram on the graph, if you have so much dynamic range the camera can't keep the whole curve on the graph, let the shadow side go off to the left.
12-12-2015, 11:08 AM   #6
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QuoteOriginally posted by admanat Quote
I know this is a topic discussed many times, but I just wanted to see if anyone else has felt Pentax K5 at ISO 80 produced unnatural looking results especially in the highlights - I could call it compressed highlights look.
The short is "no", ISO 80 has always produced very nice images for me. One of the complaints when the k-3 came out was the lack of ISO 80.

As others have already said, please post some images with the EXIF intact to show what you mean. There are a number of settings in the camera that might have an impact and without knowing how you have things set up it is difficult to give much advice. In particular are you shooting jpeg or RAW?

As Norm says above you also need to expose properly. I call it expose to the right, though Norm says left but we mean the same thing. Keep the right side of your histogram as close to the edge as you can but never, ever go over. If you have to pull shadows that's OK, but highlights are tough to recover.
12-12-2015, 11:16 AM   #7
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QuoteOriginally posted by jatrax Quote
As Norm says above you also need to expose properly. I call it expose to the right, though Norm says left but we mean the same thing. Keep the right side of your histogram as close to the edge as you can but never, ever go over. If you have to pull shadows that's OK, but highlights are tough to recover.
I guess I should change my terminology.. is that the convention?
12-12-2015, 12:09 PM   #8
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Thanks for your input.

I don't have a single image to give an example of what I say by 'compressed highlight look', and even if I did at web display size it will not be objective enough. The only option for me is to shoot at ISO 100 for a few days and compare the results for myself.

But I have to say that I'm not happy with ISO 80 images.

12-12-2015, 12:12 PM   #9
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QuoteOriginally posted by admanat Quote
After reading some more online, it seems extended ISO is basically software pulling or pushing the histogram. Lets say if you shoot at ISO 80, the camera shoots at ISO 100,
QuoteOriginally posted by normhead Quote
The trick with the K-5 is expose to the left. It's much more forgiving of under-exposed shadows than it is of blown out high lights.
Technically, on the K-5, ISO80 is really ISO80 and it is an option given by the sensor manufacturer to bias the sensor with a higher voltage level, and that means that the sensor full well capacity is pushed closer to pin junction breakdown voltage, statistically the life time of the sensor is reduced with a higher risk of triggering hot pixels over time. That option wasn't possible on the K-3 because the risk of blowing pixels was too high, otherwise it would have been implemented like on the K-5 series. With the K-5 at ISO80, if pixels are blown up, it's a simple exposure problem, not related to ISO80.
12-12-2015, 12:37 PM   #10
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QuoteOriginally posted by jatrax Quote
The short is "no", ISO 80 has always produced very nice images for me. One of the complaints when the k-3 came out was the lack of ISO 80.

As others have already said, please post some images with the EXIF intact to show what you mean. There are a number of settings in the camera that might have an impact and without knowing how you have things set up it is difficult to give much advice. In particular are you shooting jpeg or RAW?

As Norm says above you also need to expose properly. I call it expose to the right, though Norm says left but we mean the same thing. Keep the right side of your histogram as close to the edge as you can but never, ever go over. If you have to pull shadows that's OK, but highlights are tough to recover.
I think you and Norm are saying different things. Norm is talking about underexposing images somewhat in order to be sure that the highlights are preserved. You are talking about getting as close to over exposure as you can while not clipping the highlights. My experience with iso 80 on the K5 and K5 II is that you can under expose a little bit and bring up the shadows without too much problem, in general.

12-12-2015, 02:00 PM   #11
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IN your image above, the way I would deal with the sun, because no matter what you do, the sun is going to be blown out, or the whole rest of the image is going to be dark, I generally adjust the exposure chimping. I get the sun to be the size I want it to be and go from there. IN this case, exposure determines the actual size of the sun in your image. This is not a calculable exposure issue. It's pretty much trial and error only, at least that's the way I do it. If, I'm in a hurry I just bracket every shot and choose later, which is probably the only safe way to make sure you get a useful exposure.

Oh and jatrax and I are talking about the same thing, just expressing it differently. If you understand what he described and what I described you'll be doing the same thing. The basic thing is line your highlights up to the right of the histogram so you don't over-expose them, letting the histogram run off the left side if you can't get everything in. I would add, once your histogram falls to less than you DR of your camera, I usually expose to the left, you get better contrast to the left of the histogram. Then I might be under-exposing. But that's whole different conversation.
12-12-2015, 02:08 PM   #12
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QuoteOriginally posted by normhead Quote
This is not a calculable exposure issue. It's pretty much trail and error only,
Sorry, it's not a trial and error, you need to improve your technique. No need to bracket, set your camera to center AE with +2ev of exposure compensation, move the center point to the brightest point of the frame and press AE-Lock, then recompose and press the shutter: the exposure will be the best possible achievable exposure.
12-12-2015, 02:24 PM - 1 Like   #13
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QuoteOriginally posted by biz-engineer Quote
Sorry, it's not a trial and error, you need to improve your technique. No need to bracket, set your camera to center AE with +2ev of exposure compensation, move the center point to the brightest point of the frame and press AE-Lock, then recompose and press the shutter: the exposure will be the best possible achievable exposure.
Or just bracket. One push of the button, done. During a sunset like this you have 15 minutes to get every image you want to get.It goes by very quickly you don't have time to mess around.

I've seen a 15 degree turn during recomposing, take my preferred exposure from +2 EV to -2EV for an exposure. In situations like that I don't press buttons, and I don't recompose. I shoot , shoot , shoot. Do it your way if you want. Experience tells me not to.

Bracketing allows me to take many different shots, focal length changes, different positions, lens changes etc in a very short period of time. in a very short period of time during changing conditions.... if you futz around, you'll miss keepers. In fact I've been out with guys like you on photo trips who ended up getting 1/3 the good images I did, and ended up shooting from one location instead of 3 or 4, and didn't even get the image I liked best, because they were futzing about. When it's time to work, go , go go, is the thing.







12-12-2015, 05:19 PM   #14
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I have to agree with Norm,
Bracketing is the way to go in these extreme contrast situations,
I have an "HDR" mode I created in both my K5 & K3, get 5-frames at 0.7 stop apart, with one push, sometimes I stack them, sometimes i pick one frame out.

Having learned with film, it took a long time for me to get used to the idea that there is no penalty for taking more shots with digital, only a regret of not taking more . If it's really garbage, delete it later, but I'd rather have a frame to work from than to only have a memory of what could have been.

and back to the OP's original point, 80 to 100 is only 1/3 of a stop, the camera's dynamic range covers it nicely, maybe i'm not picky enough, but I've never noticed a big difference, To me the K3 & The K5 perform pretty much the same at the bottom of the ISO range.
12-12-2015, 05:46 PM   #15
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QuoteOriginally posted by Rondec Quote
I think you and Norm are saying different things.
Nope, we are on the same page, just saying it differently.
QuoteOriginally posted by normhead Quote
If you understand what he described and what I described you'll be doing the same thing. The basic thing is line your highlights up to the right of the histogram so you don't over-expose them, letting the histogram run off the left side if you can't get everything in.
^^^^^ What he said. Basically I just pay attention to the right side and let the left side take care of itself. If that means it runs off the left side, so be it.
QuoteOriginally posted by normhead Quote
I guess I should change my terminology.. is that the convention?
No idea, maybe I'm wrong. I just know I try to keep as much on the right of the histogram as I can but never go over. I call it "The price is right metering" the closer you get to the right the better, but if you go over you failed.


And I always bracket at sunrise / sunset. Sometimes they get blended, sometimes I just use one frame but with time short, why not bracket? The camera makes it simple.
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