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02-11-2007, 05:51 PM   #1
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K10D - why the High ISO with flash?

was wondering if anybody noticed that the K10D seems to max out the ISO (when in auto ISO), even when you are using the flash.

I have my auto ISO range set to 100-800. I understand why ISO would be high for an available light photo, but why for a flash photo? Its almost as if the auto-ISO algorithm does not take into account use of the flash.

The problem is the high ISO introduces noise in the picture which I don't want and which I would think is unnecessary.

Any help or opinions are welcome.

02-11-2007, 06:11 PM   #2
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"auto-ISO algorithm does not take into account use of the flash"

it might well not do.. i cant see any valid reason for bumping the noise up unless u have to.. to extend flash range yes.. but only then.. i think the k100 uses a lower iso unless it needs to up it..

little bugs and quirks happen..

trog
02-11-2007, 06:20 PM   #3
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I also posted on another board, and ironically someone else created an identical thread. That owner also owned the older pentax dslr which they stated does not exhibit this issue.
02-11-2007, 07:28 PM   #4
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QuoteOriginally posted by loganross Quote
was wondering if anybody noticed that the K10D seems to max out the ISO (when in auto ISO), even when you are using the flash.
Yes, this is how it works. And it looks like it was done on purpose - afterall, we set the upper limit of the Auto ISO ourselves, and presumably this implied that we would be happy with images within that ISO range. In a way, it does make sense. Having higher ISO has the advantage of increased flash range and better balance between ambiance and flash light (what the camera strives for judging by the shutter speed chosen).

If you don't like it, just override it by dialing in your own ISO, or set a lower limit for the Auto ISO.

02-11-2007, 07:31 PM   #5
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correct me if I am wrong but it was my understanding that the flashes light output was not automatically varied and instead was only varied manually by using flash compensation. If this is this case, then the notion of camera automatically balancing flash vs ambiance would not be correct.

thanks in advance for your response.
02-11-2007, 07:47 PM   #6
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QuoteOriginally posted by loganross Quote
was wondering if anybody noticed that the K10D seems to max out the ISO (when in auto ISO), even when you are using the flash.

I have my auto ISO range set to 100-800. I understand why ISO would be high for an available light photo, but why for a flash photo? Its almost as if the auto-ISO algorithm does not take into account use of the flash.

The problem is the high ISO introduces noise in the picture which I don't want and which I would think is unnecessary.

Any help or opinions are welcome.

I'm with Trog on this one. You may have been taking a shot in a spot that was so poorly lit, that the camera's programming chose the upper end of the Auto-ISO selection. The camera will do this regardless if the flash is on or off in this situation, but will compensate with the higher shutter speed when the flash is up and it goes through the P-TTL sequence.

Only way around this is to manually override your ISO.
02-11-2007, 07:53 PM   #7
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QuoteOriginally posted by loganross Quote
correct me if I am wrong but it was my understanding that the flashes light output was not automatically varied and instead was only varied manually by using flash compensation. If this is this case, then the notion of camera automatically balancing flash vs ambiance would not be correct.
There are two types of situations the camera would encounter during the normal flash mode - the usual low light flash photography and the daylight fill flash.

For our usual low light photography, the ambient light level is too low for hand holdable shots, so the main illumination would be from the flash. So here, the main exposure would be done by P-TTL managing the flash exposure, while the camera would set a shutter speed as low as possible for hand holdable shots depending on the focal length of the lens (1/focal length x 1.5 rule). The would allow as much ambient light as possible. And using a higher ISO would allow more ambient light for the same shutter speed.

In fill light situations, the ambient light level is high enough for a good exposure without the use of a flash. In this situation, the camera would meter the scene for a good exposure with selected aperture and shutter speed; while the P-TTL would adjust the flash output to fill any shadows of the subject.

And you can change the balance between ambient vs flash light by using flash exposure compensation (changing the flash output), and EV Exposure compensation (change BOTH the flash output and camera metering). In the first situation when ambient light level is very low, change EV and Flash exposure compensation has the same effect, since the main illumination of the scene is from the flash.

With a tripod or within SR manageable range, you can also use Slow Speed Sync, this would allow the camera to use as low a shutter speed as possible to get a good balance between ambient and flash light.
02-11-2007, 08:20 PM   #8
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Is it consistent across the board or does it pick higher iso with further distances too? I know that if you use the onboard flash it has limited throw that is increased with higher iso. It also may use higher iso to give the picture a more available light feel. If you use only the flash it will expose the foreground and the background will be virtually black.

Sorry, I had not refreshed since all of the replies appeared. I guess great minds think alike

02-11-2007, 11:11 PM   #9
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I have the same issue and it bugs me as well.

the k10 never leaves ISO 800 in auto mode(I have the upper limit at 800) when I am using my flash. this doesn't make for very good enlargement, IMHO
when I was at a cheerleading event this past weekend, I wanted lower ISO for enlargements. I used the ISO priority and put the ISO to 100. I would not for the life of me get the K10 to expose properly until ISO 500... even then if I looked at the unaltered .dng photo, they are all still underexposed by about one stop.
but.... when the same flash is put on my wife's k100, there are no exposure issues at all. the subject can be 50 feet away and she can still freeze action with great exposure.
not with my K10
I tired all the different priorities and the sensitivity priority was the only one that gave close to the right exposure, but still 1 stop dark in .dng.

sure some photos look the best when the most ambient light is mixed in, but when trying to capture a girl in the air doing a cheerleading stunt, you want the subject to be clear as possible with just a tiny bit of blurr in the right body parts to make it look real.

I am hoping and praying that when adobe releases the raw update this month, that the raw coming from the k10 is processed a lot better. hell, using the k10 and a flash in .dng right now, I even get a lot of noise even at 400 ISO

but how do you figure out if it is the camera or the flash?

the k10 gets very low noise and great exposure outdoors.

cheers

randy
02-12-2007, 12:33 AM   #10
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QuoteOriginally posted by slipchuck Quote
I would not for the life of me get the K10 to expose properly until ISO 500... even then if I looked at the unaltered .dng photo, they are all still underexposed by about one stop.
but.... when the same flash is put on my wife's k100, there are no exposure issues at all. the subject can be 50 feet away and she can still freeze action with great exposure.
not with my K10
I don't quite understand this. If you use the same aperture and shutter speed and ISO (and lenses) with K10D and K100D, you should get the same exposure - no? If you get underexposure from the flash, you need to dial in some flash exposure compensation (check histogram).

I won't hesitate to go up to ISO 1600 to get proper exposure and good freeze in the motion. It is no point having a noise free blur

With good exposure, K10D's ISO 1600 is not too bad in noise, and it does clean up nicely with Noice Ninja.

Maybe you can give Bibble a try; it has built-in DNG support and Noise Ninja built-in. There is a free trial version downloadable.
02-12-2007, 08:23 AM   #11
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I am going to call Pentax today. I find it very hard to believe that the K10D intentionally maxes out ISO for every flash shoot. Especially when no other Pentax SLR exhibits this behavior. I like my K10D and I get better everyday with it. But this appears to be a bug which is very illogical, but can be easily fixed.

I am pressing so hard because of the following commonly occurring scenario: An indoor shoot with relatively low light but certainly not darkness. I can take the shoot with available light and my 1.4 lens and can get a very good shot, but I would have to use ISO 800 because living subjects don't sit perfectly still. What's the alternative? Use flash and the same 1.4 lens. Logically ISO would decrease, and the result would be a crisper picture, better opportunity to stop motion without blur, and none of the noise or banding associated with ISO 800 on the K10d.

BTW, yes I could use Sv mode or some other mode, but why would I want to. It would seem to me that ISO is the easiest of the variables for the camera to determine. Moreover, I like P mode coupled with the MTF program line.

In addition to the user above who mentioned no like problem witht he K100d, this is a quote from another user experiencing the same difficulty but having positive previous experience with an older pentax dslr. "On my DS/DL, they're also on auto iso (200-3200) and when I take a similar shots with the flash up, they take it at iso-200."

Last edited by loganross; 02-12-2007 at 08:30 AM.
02-12-2007, 08:48 AM   #12
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QuoteOriginally posted by nosnoop Quote
I don't quite understand this. If you use the same aperture and shutter speed and ISO (and lenses) with K10D and K100D, you should get the same exposure - no? If you get underexposure from the flash, you need to dial in some flash exposure compensation (check histogram).

I won't hesitate to go up to ISO 1600 to get proper exposure and good freeze in the motion. It is no point having a noise free blur

With good exposure, K10D's ISO 1600 is not too bad in noise, and it does clean up nicely with Noice Ninja.

Maybe you can give Bibble a try; it has built-in DNG support and Noise Ninja built-in. There is a free trial version downloadable.
You would think that they would be the same.... but for some reason the K100 works much better with the same flash and camera settings

randy
02-12-2007, 08:49 AM   #13
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QuoteOriginally posted by loganross Quote
I am going to call Pentax today. I find it very hard to believe that the K10D intentionally maxes out ISO for every flash shoot. Especially when no other Pentax SLR exhibits this behavior. I like my K10D and I get better everyday with it. But this appears to be a bug which is very illogical, but can be easily fixed.

I am pressing so hard because of the following commonly occurring scenario: An indoor shoot with relatively low light but certainly not darkness. I can take the shoot with available light and my 1.4 lens and can get a very good shot, but I would have to use ISO 800 because living subjects don't sit perfectly still. What's the alternative? Use flash and the same 1.4 lens. Logically ISO would decrease, and the result would be a crisper picture, better opportunity to stop motion without blur, and none of the noise or banding associated with ISO 800 on the K10d.

BTW, yes I could use Sv mode or some other mode, but why would I want to. It would seem to me that ISO is the easiest of the variables for the camera to determine. Moreover, I like P mode coupled with the MTF program line.

In addition to the user above who mentioned no like problem witht he K100d, this is a quote from another user experiencing the same difficulty but having positive previous experience with an older pentax dslr. "On my DS/DL, they're also on auto iso (200-3200) and when I take a similar shots with the flash up, they take it at iso-200."
please let us know how you make out

cheers

randy
02-12-2007, 08:50 AM   #14
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Easy solution to the problem - Don't use AUTO anything! When I shoot flash, I usually go into Manual mode, set the ISO to 400, shutter speed to 1/125, and then the aperture to whatever DOF I want (usually keep it around f/4.5 though). This way the only thing the camera decides is how much flash power to use. And it's usually pretty accurate.

If I'm in a big room/high ceiling, I might go to ISO800. If the background needs more exposure, I might lower the shutter speed to 1/100 or so.

If you want to get the best out of your camera, don't let it set stuff for you. :-)

When I go flash-less, I just go into Av mode and alway keep an eye on the shutter speed. If it gets to be too slow for the aperture I want, I boost the ISO.
I hit the limit of my f/2.8 zoom this weekend. In our basement at night, just regular tungsten lighting. I was (well the lens was) wide open (f/2.8), ISO3200, and I still could only get away with 1/80s or so. I was using my flash but the batteries died

I should have grabbed by 50mm f/1.4, then I could have backed down to ISO800 :-) (I love using that lens wide open!)
02-12-2007, 08:55 AM   #15
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u are in a position to know slipchuck.. u have both cameras to test them side by side..

hows about swapping sides and becoming the "expert" for a while.. u give the rest of us some answers..

trog

ps.. as for "automatics" i might be in a minority here but i expect them to "mostly" work.. i judge a good camera from a bad camera on how well its automatics work.. all cameras need some help.. but a good a camera needs less help than a bad camera.. the less fiddling with settings i have to do the better..

Last edited by trog100; 02-12-2007 at 09:02 AM.
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