Flash and Auto ISO

deathspared · 02-15-2009, 09:35 PM

I am pretty sure on my K100D when I had the auto ISO set and I popped up the flash it automatically went to the lowest ISO.

With my new K200D, the ISO stays at the same as without the flash which is annoying. There is no reason for me to shoot at ISO 800 with flash.

Anyone else notice this change and is frustrated by it?

AndrewG NY · 02-17-2009, 10:24 AM

I disagree with that statement--flash is not a replacement for increasing ISO. Raising ISO makes the most of the ambient light and flash power. Particularly with the weak (and direct-flash-only) built-in flash, using ISO 800 sounds like a pretty good idea most of the time. Combining higher ISO with flash will often make for a less 'flashy' shot. If you want to force lower ISO with flash, the camera certainly has the controls to allow it.

I'm assuming you're talking about low-light scenario; when I shoot flash, I usually use manual mode with ISO set in the 400-640 range. Note that P-TTL flash is basically an autoexposure mode, even if camera is set to manual. I would typically set ISO 400-640, aperture f/5.6-8, and shutter speed from 60-125, and let the P-TTL flash make up the difference, adjusting exposure to taste using flash compensation. If you use an autoexposure mode such as P, the camera would probably choose a lower shutter speed, a wider aperture, and a higher ISO (as you observed). I tend to prefer a little more depth-of-field & improved lens performance, & a little higher shutter speed as safety for camera shake.

deathspared · 02-17-2009, 07:22 PM

It would be nice to have a menu option to have separate ISO settings when flash is up. That would be pretty simple and convenient.

AndrewG NY · 02-17-2009, 08:29 PM

Perhaps. I guess the designers always have to toe the line between convenient and simple. With your K200D if you want quick control of ISO you can also use Sv shooting mode.

mattdm · 02-17-2009, 08:38 PM

Originally posted by deathspared

It would be nice to have a menu option to have separate ISO settings when flash is up. That would be pretty simple and convenient.

Yeah. With my K10D, I use USER mode for exactly this reason.

I'm curious about the program logic the K200D. With the K10D in P mode, it seems to always prefer shutter speeds of about focal length × 1.5. The aperture selected, however, is dependent on the ISO, with a "hard" cutoff: if ISO is 400 or above, it prefers to be around f/8. When I go below 400 (even 320), suddenly it prefers to go to f/2.8. (Which is the fastest of any automatic lens I have — not sure what it'd do with an FA f/1.4.)

AndrewG NY · 02-17-2009, 08:57 PM

Originally posted by mattdm

Yeah. With my K10D, I use USER mode for exactly this reason.

I have yet to find a good use for USER mode. I'm glad you found one.

Originally posted by mattdm

I'm curious about the program logic the K200D. With the K10D in P mode, it seems to always prefer shutter speeds of about focal length × 1.5. The aperture selected, however, is dependent on the ISO, with a "hard" cutoff: if ISO is 400 or above, it prefers to be around f/8. When I go below 400 (even 320), suddenly it prefers to go to f/2.8. (Which is the fastest of any automatic lens I have — not sure what it'd do with an FA f/1.4.)

That sounds a little weird, I've never noticed anything like that. Aperture seems to move 1/3 step at a time for me as I decrease ISO.

02-15-2009, 09:35 PM	#1
deathspared Forum Member Join Date: Jul 2008 Location: san jose, ca Posts: 78	Flash and Auto ISO I am pretty sure on my K100D when I had the auto ISO set and I popped up the flash it automatically went to the lowest ISO. With my new K200D, the ISO stays at the same as without the flash which is annoying. There is no reason for me to shoot at ISO 800 with flash. Anyone else notice this change and is frustrated by it?

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02-17-2009, 10:24 AM	#2
AndrewG NY Veteran Member Join Date: Dec 2006 Location: Chappaqua, NY Photos: Gallery Posts: 688	I disagree with that statement--flash is not a replacement for increasing ISO. Raising ISO makes the most of the ambient light and flash power. Particularly with the weak (and direct-flash-only) built-in flash, using ISO 800 sounds like a pretty good idea most of the time. Combining higher ISO with flash will often make for a less 'flashy' shot. If you want to force lower ISO with flash, the camera certainly has the controls to allow it. I'm assuming you're talking about low-light scenario; when I shoot flash, I usually use manual mode with ISO set in the 400-640 range. Note that P-TTL flash is basically an autoexposure mode, even if camera is set to manual. I would typically set ISO 400-640, aperture f/5.6-8, and shutter speed from 60-125, and let the P-TTL flash make up the difference, adjusting exposure to taste using flash compensation. If you use an autoexposure mode such as P, the camera would probably choose a lower shutter speed, a wider aperture, and a higher ISO (as you observed). I tend to prefer a little more depth-of-field & improved lens performance, & a little higher shutter speed as safety for camera shake.

02-17-2009, 07:22 PM	#3
deathspared Forum Member Join Date: Jul 2008 Location: san jose, ca Posts: 78 Original Poster	It would be nice to have a menu option to have separate ISO settings when flash is up. That would be pretty simple and convenient.

02-17-2009, 08:29 PM	#4
AndrewG NY Veteran Member Join Date: Dec 2006 Location: Chappaqua, NY Photos: Gallery Posts: 688	Perhaps. I guess the designers always have to toe the line between convenient and simple. With your K200D if you want quick control of ISO you can also use Sv shooting mode.

02-17-2009, 08:38 PM	#5
mattdm Veteran Member Join Date: Feb 2007 Location: Boston, MA Photos: Gallery Posts: 2,948	Originally posted by deathspared It would be nice to have a menu option to have separate ISO settings when flash is up. That would be pretty simple and convenient. Yeah. With my K10D, I use USER mode for exactly this reason. I'm curious about the program logic the K200D. With the K10D in P mode, it seems to always prefer shutter speeds of about focal length × 1.5. The aperture selected, however, is dependent on the ISO, with a "hard" cutoff: if ISO is 400 or above, it prefers to be around f/8. When I go below 400 (even 320), suddenly it prefers to go to f/2.8. (Which is the fastest of any automatic lens I have — not sure what it'd do with an FA f/1.4.)

02-17-2009, 08:57 PM	#6
AndrewG NY Veteran Member Join Date: Dec 2006 Location: Chappaqua, NY Photos: Gallery Posts: 688	Originally posted by mattdm Yeah. With my K10D, I use USER mode for exactly this reason. I have yet to find a good use for USER mode. I'm glad you found one. Originally posted by mattdm I'm curious about the program logic the K200D. With the K10D in P mode, it seems to always prefer shutter speeds of about focal length × 1.5. The aperture selected, however, is dependent on the ISO, with a "hard" cutoff: if ISO is 400 or above, it prefers to be around f/8. When I go below 400 (even 320), suddenly it prefers to go to f/2.8. (Which is the fastest of any automatic lens I have — not sure what it'd do with an FA f/1.4.) That sounds a little weird, I've never noticed anything like that. Aperture seems to move 1/3 step at a time for me as I decrease ISO.