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04-07-2011, 05:17 PM   #451
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QuoteOriginally posted by Eruditass Quote
What about spot meter mode?
It helps if it is aligned with the selected AF area, but you still need the target to be (overall equivalent to) 18% gray for the camera settings to reflect the target brightness.

QuoteOriginally posted by jstevewhite Quote
One might presume that, for a correct exposure, ISO+f-stop+shutter speed (not additively, but from those bits of data) one might derive the EV of the scene within some fairly reasonable error margin.
As above. It only works for 18% gray targets. The error margin is very high for targets strongly deviating from 18% gray.

What I was wondering was whether the LV values recorded by the camera (PhotoME shows a graphic display of them) are independent of camera settings.

QuoteOriginally posted by jstevewhite Quote
That said, I'm pretty sure my K-5 is slightly slower than advertised ISO; using the Sunny 16 rule, I consistently see 1/4 to 1/2 stop underexposure, regardless of metering mode.
You can check out the DxOMark measurements for the K-5 to see the difference between nominal and real ISO.

05-27-2011, 06:22 AM   #452
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So, what can we realistically expect? I'm not sure I understand how Falconeye adjusts the EV (as explained in chapter 2.2 of his study here).

I guess the real question for me is : using the same lens as in the tests (FA 31), is it "normal" to get front focus at something around EV 3 and below in tungsten light? Here I mean the theoretical EV value calculated with iso/aperture/speed, not the LV value used by Falconeye that I don't quite understand.

In other words, is my camera as good as it gets, or should it be better?
05-27-2011, 07:08 AM   #453
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QuoteOriginally posted by PhilippeG Quote
Here I mean the theoretical EV value calculated with iso/aperture/speed, not the LV value used by Falconeye that I don't quite understand.
The problem is that you may not fully understand what the EV value means. If it stands for the shutter/aperture/iso triplet as it is normally meant then EV is different from LV which is a light value.

EV only equals LV if you shoot an 18% gray surface in daylight and it turns out ~50% gray in sRGB after the shot.

The only way to do a reproducible test is by using a well defined light value.

It is very easy for a camera to meter EV4 in a LV0 test situation. E.g., just make the target bright red. I explained it in the paper. I.e., at EV4, the red will turn out dim and green and blue will be dark which then corresponds to LV0 rather than LV4 in my book.
05-27-2011, 08:01 AM   #454
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Oh yes, now I get it. Thank you for your explanation!

02-26-2012, 10:26 AM   #455
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So what is the verdict on this subject? We are up to firmware 1.12. Has Pentax been able to address the subject?

I shot an event last night with my new K-5 (Sigma 50, 85, & DA*200) Micro-AF was adjusted for each lens with the Sigma 85mm needing +2 (only lenses that needed any adjustment in good light). Stage was lit by multicolored LED spots. I ended up setting all lenses to -10. Shooting at ISO3200, F/2.8, 1/80 which was 1 stop under exposed to keep from blowing highlights from the spotlights.

While the K-7 had noise to deal with under these conditions, the AF was much more accurate. Noise is much easier to deal with.
02-26-2012, 04:40 PM   #456
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QuoteOriginally posted by Winder Quote
So what is the verdict on this subject? We are up to firmware 1.12. Has Pentax been able to address the subject?

I shot an event last night with my new K-5 (Sigma 50, 85, & DA*200) Micro-AF was adjusted for each lens with the Sigma 85mm needing +2 (only lenses that needed any adjustment in good light). Stage was lit by multicolored LED spots. I ended up setting all lenses to -10. Shooting at ISO3200, F/2.8, 1/80 which was 1 stop under exposed to keep from blowing highlights from the spotlights.

While the K-7 had noise to deal with under these conditions, the AF was much more accurate. Noise is much easier to deal with.
Hmm... My K-5 seems to be much, much more accurate on AF under all conditions than my K-7 was.
In fact, I never have seen the low light focus issue with my K-5.
02-26-2012, 06:37 PM   #457
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QuoteOriginally posted by Ubuntu_user Quote
Hmm... My K-5 seems to be much, much more accurate on AF under all conditions than my K-7 was.
In fact, I never have seen the low light focus issue with my K-5.
My K-5 is spot on with all my lenses in most light. But last night it was awful. The 85mm ended up giving me the best luck, but if I went faster than F/2.8 it all fell apart. I adjusted it to -10 and I was able to shoot the show but still only had 25% with good focus. This was a charity event but on March 22nd I have a paid gig at this venue. The red/orange LED stage lights really gave me a bad front focus. I had 12 shots that focus nailed, but once I realized AF was going to be hit and miss I was firing away. 460 shots 12 with really crisp focus, another 30 or so with really good focus or slight subject blur due to motion, and the rest are just crap. I'll have a couple of more chances to shot there before the 22 to see if I can get it worked out.

I set the AF focus test back up this afternoon and re-adjusted all my setting. AF is spot on will all lenses except the Sigma 85mm which is still at +2. Took the 85mm out today for a walk and ran through a hundred frames. Spot on AF and razor sharp from F/2 up.

My K-7 was slow, but I shot in the venue last summer with the K-7 and the Sigma 50mm with no trouble. Most shots taken at F/2. I had noise to deal with, but Topaz and LR3 did wonders for the K-7 noise. Last summer they had tungsten spots, but this time they had a new LED system.
02-26-2012, 08:24 PM   #458
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QuoteOriginally posted by Winder Quote
Stage was lit by multicolored LED spots.
Suggest you see UnknownVT's extensive and informative thread(s) that discuss the perils of shooting under LED spots, which include their effects on AF and AE... it's not just something that impacts the K-5:
Modern LED Stage Lighting & photography problems
and including:
K-x in Use


Last edited by rawr; 02-26-2012 at 08:29 PM.
02-26-2012, 10:26 PM   #459
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QuoteOriginally posted by rawr Quote
Suggest you see UnknownVT's extensive and informative thread(s) that discuss the perils of shooting under LED spots, which include their effects on AF and AE... it's not just something that impacts the K-5:
Modern LED Stage Lighting & photography problems
and including:
K-x in Use
I read through that, but I was not having those problems. My colors were good all things considered. Once I set my AF Adjust to -10 things got much better, but still not perfect. If I dropped below F/2.8 focus fell back off. When focus was nailed it was really sharp, it just only nailed 12-15 images. My afternoon test shoot everything was back to normal. Really sharp, really accurate AF.

Basically, to get better results I had to set AF to -10 for all three lenses and keep aperture at F/2.8 or smaller.

The LED thread is good information though. I am seeing more and more LED. Especially in small venues.
02-27-2012, 04:57 PM   #460
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Is it off-topic to wonder whether there is anything we could do to make sure that Falk (falconeye) receives a copy of the K-5 successor model to check its low light AF?

If it passes, I'll promise to buy one (or a Pentax FF ).
02-27-2012, 11:16 PM   #461
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As a fact, a couple tenths people can give 20-30 euros, he would get one...
02-28-2012, 04:27 PM   #462
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QuoteOriginally posted by Class A Quote
Is it off-topic to wonder whether there is anything we could do to make sure that Falk (falconeye) receives a copy of the K-5 successor model to check its low light AF?

If it passes, I'll promise to buy one (or a Pentax FF ).
With so many people all using the same Sony sensors it is important that Pentax improve its support technologies to separate itself from everyone else. AF accuracy is really important in any light that the camera functions in. My AF was locking very fast, it was just wrong. I was only pushing ISO3200, so I was not really pushing the low light abilities.

I don't think Pentax AF is slow when using Sigma glass with HSM. SDM is the slower component of the current system. The first chance I had to test a Sigma 85mm was on a Canon 7D and it was fast. I expected a drop in speed on the K-5, but honestly I don't think there is a noticeable drop off.

The ISO 3200 good shots cleaned up really well and fast in Topaz DeNoise with no real loss in detail. ISO6400 needed a little work, but 6400 was unusable on the K-7 for anything but grainy B&W (which do a lot of). The SR is also much improved. Lots of times my K-7 found focus long before SR was ready.
02-28-2012, 04:34 PM   #463
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I've used a friends D90, D7000 and Canon 70D, maybe its the lens but their autofocus is slightly slower. It would move to focus but then gets it right on the spot, my Pentax on the other hand would move the focus really fast go over slightly moves back then gets it right. Due to the speed Pentax seems to be faster for me, and when I used the Nikon and Canons they feel awefully sluggish. I didn't time it, but it just felt they were slower and the Pentax was faster. Maybe they ended up being the same speed or maybe the Pentax was faster or slower, it doesn't matter though the difference is tiny. So in terms of AF.S focusing I believe Pentax has well caught up or even exceeded for similar priced bodies.

Where Pentax loses to me is on AF.C it just doesnt seem to track as well as the other 3 I tried.
02-28-2012, 05:07 PM   #464
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QuoteOriginally posted by Verglace Quote
I've used a friends D90, D7000 and Canon 70D, maybe its the lens but their autofocus is slightly slower. It would move to focus but then gets it right on the spot, my Pentax on the other hand would move the focus really fast go over slightly moves back then gets it right. Due to the speed Pentax seems to be faster for me, and when I used the Nikon and Canons they feel awefully sluggish. I didn't time it, but it just felt they were slower and the Pentax was faster. Maybe they ended up being the same speed or maybe the Pentax was faster or slower, it doesn't matter though the difference is tiny. So in terms of AF.S focusing I believe Pentax has well caught up or even exceeded for similar priced bodies.

Where Pentax loses to me is on AF.C it just doesnt seem to track as well as the other 3 I tried.
I sold all my Canon gear back in December. I used my 135L on a 7D on several occasions and loved the AF speed. At the time I had the K-7 and it was night and day difference over any Pentax lens I tried. I think a lot of it has to do with the speed of SDM or screw drive. HSM and USM are noticeably faster. The first SDM lens I was able to try was the DA*55mm and it is just slow compared to other lenses in its class. I used a 5D for years and it has pretty average AF speed, so I don't see much of an issue with the K-5 AF speed. I do see an issue with accuracy.
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