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10-21-2011, 03:38 AM   #1
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K5 vs k7 dynamic range

Hi, anybody knows how much K5's dynamic range is improved comparing to K7's? I have K-5 just a couple of days now, but something i must be doing seriously wrong, because even with underexposure and highlights correction i get burned out highlights. Now I thought that in real life many of scenes would probably exceed dynamic range of either K-5 or K-7, but being inquisitive i did a very quick (not very properly done ) test. I took 4 photos from my room with windows and bright sky. First two photos by K-7, one with highlight correction ON, other with OFF. Then same scene with K-5, one with and one without highlight correction. All photos taken in Muted mode, and RAW.
Now by comparing histograms: K-7 and K-5 exposures with highlight correction ON look moreless the same. On the other side photos taken with highlight correction OFF reveal something strange: K-7 photo is okay, but K-5's show a tiny bit of burned out highlights (while exposures are same for both cameras). This is surprising me as all the reviews indicated huge improvement in Dynamic Range for K-5.
Sorry for rubbish test photos

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10-21-2011, 04:20 AM   #2
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It's been my general experience with the K5, directly out of the box, it will over expose by up to a full stop. It also depends on what lens is on the camera. Even with the great DR of the K5, one still needs to get the exposure close. I find that I spend most of my time with the camera set for EV Comp at -1 (spot metering) and I'm usually able to nail it. Of course with spot metering, What you set the EV Comp at depends more on what you are aiming at rather than the overall scene. For the semi auto modes (Av Tv) I have the EV Comp programmed to the front wheel so I can change it on the fly. ISO is set for auto from 80-32000. These settings typically work quite well for me. For your White curtain shot as an example, I would set EV Comp to +1 or even higher.

As for comparing actual DR between the K7 and K5, I loved my K7, it is a fine solid camera but, there is no contest between the two.

10-21-2011, 04:35 AM   #3
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I haven't had any exposure problems with my K-5 (nor the K-7), but the dynamic range and the low light/high iso of the K-5 is superior compared to the K-7. Only digital camera that has really changed my way of shooting since it can do so much that was impossible with the earlier models.
10-21-2011, 07:09 AM   #4
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i also have to keep EV comp at -2/3 or -1EV in order to not get significant overexposed areas

10-21-2011, 08:27 AM   #5
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-1 for me too !
10-21-2011, 11:41 PM   #6
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Hi guys, thanks for your replies. I think that it is pretty normal to deliberately underexpose with Pentax cameras, as they are better with handling the shadows than lights. So if I'm metering for '18% grey' with some bright areas in frame I always dial -2/3 EV compensation. That is not a problem, what i try to hint at this topic is that somehow I fail to see huge advantage in K-5's dynamic range over K-7. Either K-7 is not that bad as it is commonly believed or I'm making something wrong when exposing on K-5.
One difference i can see that K-7 raws have slightly more contrast, but histograms of both cameras look moreless the same.
10-22-2011, 12:47 AM   #7
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In the beginning, when I started shooting digital, I encountered that problem too.
Nothing was exposed properly!
But, I have to admit, for the exception of the Pentax LX, I hardly shot wit an AE camera. I was so used, for more than 25 years, to measure wit a spot-light meter (Pentax too) and incident-light meter (Gossen) that I simply misused the measuring system incorporated in the camera.
This was a little learning curve for me. Now I measure with the camera's system but, depending to the subject, I change from spot- over center- to full field measuring, correct it with the +/- balance and bracket a lot.
Don't trust the camera, it can't know what the real demands of the subject are (and what you want), it's only an machine and you are supposed to be on the rudder!
10-22-2011, 04:03 AM   #8
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Here 3 shots from today I'd like to throw into the discussion. The subject is not that interesting, but the exposure difficulties are. I'm just starting to use the K-5.

K5 + DA* 60-250/F4. All shoots 1/400s, f5.6, 250mm FL, TAv mode, Matrix AE, raw, no NR in PP.

1. ISO1600


Excellent noise performance after dodging in SilkyPix Pro of this ISO1600 file, compared to what I'm used to from a K20D. Shame about the blown highlights. Unrecoverable from raw. I'd suggest 1.0-1.3 EV negative exposure comp next time. Could be fixed with a fair amount of PP mucking around, if the subject was important. It looks like the AF point may have been the branch rather than the bird,


2. ISO1000


Again, good noise performance after dodging. Blown highlights would require a little bit of mucking around in PP. Maybe -0.7 EV next time.


3. ISO640


No blown highlights. If I really wanted to keep this photo, I'd blur the background in PP more as I find the bokeh too distracting.

I think acclimatising to this camera requires you to start trusting its very good noise performance and to underexpose 0.7-1.0 EV in any bright background situation.

Finally, I think all three shots look better with a bit of Clarify applied from PaintShop Pro X (similar to what's in LR). Here's the 3rd shot with Clarify(2) applied to the JPEG. (I would normally apply it to an intermediate TIFF file.) Look, for example, at the feathers on the right under the beak. (If you still can't see the difference, enter first http://users.on.net/~dosdan/K5_1/K5__4618_1.jpg in your browser's Address bar and then, after the image appears, remove the "_1" part from the URL and press Enter to refresh and you should see the difference. You can then use either your browser's Back & Forward arrows, or Alt-Left Arrow & Alt-Right Arrow hotkeys, to jump back & forth between the two versions.)




Dan.


Last edited by dosdan; 10-28-2011 at 04:00 PM.
10-22-2011, 06:28 AM   #9
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QuoteOriginally posted by vrrattko Quote
Hi guys, thanks for your replies. I think that it is pretty normal to deliberately underexpose with Pentax cameras, as they are better with handling the shadows than lights. So if I'm metering for '18% grey' with some bright areas in frame I always dial -2/3 EV compensation. That is not a problem, what i try to hint at this topic is that somehow I fail to see huge advantage in K-5's dynamic range over K-7. Either K-7 is not that bad as it is commonly believed or I'm making something wrong when exposing on K-5.
One difference i can see that K-7 raws have slightly more contrast, but histograms of both cameras look moreless the same.
The biggest issue with the K7 wasn't DR but Noise, even at the lower ISOs. The biggest advantage of the K5 over the K7 when it comes to DR is in the shadows, not the highlights.

4+ stops Under exposed..



As it came out of the camera



Pair that up with the K5's High ISO ability, low noise I might add, and you have one damn fine camera. Even with it's quirks (for some people).



Camera Pentax K-5
Exposure 0.017 sec (1/60)
Aperture f/5.6
Focal Length 50 mm (Pentax A35-105 f3.5)
ISO Speed 20000
Exposure Bias -1.3 EV

10-22-2011, 12:53 PM   #10
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QuoteOriginally posted by JeffJS Quote
The biggest issue with the K7 wasn't DR but Noise, even at the lower ISOs. The biggest advantage of the K5 over the K7 when it comes to DR is in the shadows, not the highlights.

4+ stops Under exposed..



As it came out of the camera



Pair that up with the K5's High ISO ability, low noise I might add, and you have one damn fine camera. Even with it's quirks (for some people).



Camera Pentax K-5
Exposure 0.017 sec (1/60)
Aperture f/5.6
Focal Length 50 mm (Pentax A35-105 f3.5)
ISO Speed 20000
Exposure Bias -1.3 EV


I agree with that, it seems that if i underexpose photos to avoid burned highlights i can then safely use fill light in lightroom for shadows....something i couldn't do so easily with k7. K5 iso 80 is noise free, and noise up to iso 2000 is so delicate it doesn't bother me at all - this is indeed improvement over k-7.
10-22-2011, 02:25 PM - 1 Like   #11
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It's worthwhile to consider, what, if any penalty, negative EVcomp has on the K-5. The total noise increase of shooting 4.3 stops underexposed at ISO80 (and then adjusting the EV afterwards in your raw converer) vs turning up the gain to ISO1600 to get the histogram fully to the right is only 0.6 stops. So the penalty for shooting with -1EVcomp at ISO80 or ISO100 instead of using ISO200 is probably less than 0.2 stops extra noise. But since you lose approx. 1 stop of DR for each stop increase in ISO, and this comes off the top (less headroom), this means you will have 1 extra stop of headroom, by shooting underexposed 1 stop.

Besides the small noise penalty, you also have a darker image to review in the back LCD screen, but things should work out well in PP.

For a discussion about this see:

https://www.pentaxforums.com/forums/pentax-k-5-forum/135603-isoless-sensor.html

Last edited by dosdan; 10-22-2011 at 11:39 PM.
10-22-2011, 02:53 PM   #12
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QuoteOriginally posted by dosdan Quote
It's worthwhile to consider, what, if any penalty, negative EVcomp has on the K-5. The total noise increase of shooting 4.3 stops underexposed at ISO80 (and then adjusting the EV afterwards in your raw converer) vs turning up the gain to ISO1600 to get the histogram fully to the right is only 0.6 stops. So the penalty for shooting with -1EVcomp at ISO80 or ISO100 instead of using ISO200 is probably less than 0.2 stops extra noise. But since you lose 1 stop of DR for each stop increase in ISO, and this comes off the top (less headroom), this means you will have 1 extra stop of headroom, by shooting underexposed 1 stop.

Besides the small noise penalty, you also have a darker image to review in the back LCD screen, but things should work out well in PP.

For a discussion about this see:

https://www.pentaxforums.com/forums/pentax-k-5-forum/135603-isoless-sensor.html
I'm not sure I quite understand what you mean exactly, but isn't shooting at lets say ISO200 already decreasing dynamic range and increasing contrast in comparison to shooting at ISO80? It worked like that with films and i think it works same with sensors still. I mean in that link you stated that it is better to shoot at higher ISO with proper exposure, but higher ISOs have smaller dynamic range than base ISO, right? So If I have scene which push the limits of dynamic range of sensor, how would shootin at ISO 200 or ISO 400 provide better result than ISO80?

Last edited by vrrattko; 10-22-2011 at 02:59 PM.
10-22-2011, 03:01 PM   #13
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I should mention that EVcomp works differently in Av & Tv vs TAv. In the first two modes, using negative EVcomp reduces the amount of light hitting the sensor, but with TAv it reduces the ISO (since the other two parameters are fixed). So it's only in TAv mode that I'm talking about using EVcomp to reduce the ISO.

Dan
10-22-2011, 03:02 PM   #14
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Sorry Dan, I misunderstood - you're correct....keep iso low and shoot to the left
10-22-2011, 04:04 PM   #15
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What if one were to spot meter off the highlights, without compensation?
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