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Old Dec 11, 2007, 11:35 PM   #1
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why are allllllll my pics underexposed,

and no i am not out of the flash range andi also find this even when i am not using flash ,i always end up using a +ev
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Old Dec 12, 2007, 5:44 AM   #2
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If you have not already done so, try this:

in your Custom Menu find the option to "Link AF Point and AE". The camera default is "1". Change it to "2". I have a K100D and a 360 flash and this improved the underexposure problem.

You might also want to try using the 360 in A (Auto mode). This does not use P-TTL. It relies on the sensor in the 360 flash unit to set the flash exposure. You will have to manually set ISO and F (aperature) and zoom focal length of the lens settings on the flash to match what your K10D is set for. I have gotten more consistent results with this setting than in using P-TTL. To make that a little easier, try using the K10D in Av mode and choose an F stop (aperature) that will work for the scene you are shooting, that way the F setting will stay constant and you won't have to worry about setting it for each shot on the 360 flash, just remember to set the F stop on the 360 to match what the K10D is set for. Secondly, choose a constant ISO on the K10D (instead of using an ISO range setting) and set the ISO on the 360 to match. ISO 400 should work well for low light. If you are using a prime lens, just set the zoom on the 360 to match the focal length of the lens you are using. As I said, I get better results using A (Auto) mode on the 360. Which leads to the conclusion that we could have saved a lot of money by buying a simple Auto-thyristor flash like the Vivitar 285HV instead of the AF360FGZ. I wish someone (Pentax) could design a flash that uses the A (Auto) sensor in the flash unit, but automatically sets the flash ISO, F, and Focal length that the camera is set for. I'm disappointed in the lack of consistency that P-TTL gives.
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Old Dec 12, 2007, 7:05 PM   #3
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Hi dafiryde,

As a200user suggested, linking the AE to AF point is a good idea.

IIRC, you have a K10 body, and I have found both the 360 and 540 FGZs expose pretty well in P-TTL with mine. There is the known issue of flash reflections in the frame causing significant underexposure with P-TTL, but if I avoid these, it works well.

I almost always use flash modifiers (Demb, Lightsphere, Lumiquest Mini Softbox, or Omnibounce) and bounce the flash. As an example, I shot 182 flash exposures at my recent 40th High School Reunion, and except for 2 shots where I messed up and positioned myself perpendicular to a mirrored wall causing a reflection of the flash in the frame, all were exposed well enough that they needed little exposure correction in PP. In those two shots, I knew I had blown it when I saw the reflection of the preflash in the viewfinder, so I immediately repositioned myself a bit to the side and took another shot as soon as the flash charged indicator appeared in the VF.

If you are using Matrix Metering Mode, this might be part of the problem. I generally use aperture priority for quick and dirty low light flash stuff, since both Ev and Flash exposure compensations work, but I always use spot metering mode for flash -- works pretty well for me.

If you want to "drag the shutter", using a smaller aperture and longer shutter speed to bring up the background ambient light, try using Manual Exposure Mode and Trailing Curtain Flash Synch on the flash, using the AEL button to set the exposure for the ambient light, then refame and let the P-TTL set the exposure for the flash. Relatively high ISO speeds might be needed to get as much of the background as you might want, but if the flash exposes your subject correctly, noise won't be a problem. Subject motion also shouldn't show up with the slow shutter speeds as the short flash duration should freeze any motion in the subject. This helps prevent the "correctly exposed subject with a black background" look that is often associated and generally distained with indoor flash use.

For outdoor fill flash, try High Speed Synch (you have to set up for this on both the camera body and the flash), Manual Exposure Mode, set the shutter speed and aperture to correctly expose the background with the AEL button (you can use as high a shutter speed as the exposure needs), and then reframe and let P-TTL set the exposure for the flash. This prevents the blown out backgrounds that result from correctly exposing a backlit subject in daylight without the flash.

P-TTL might not be as sophisticated as some of the other preflash DSLR systems, but I think it's far from being as disfunctional as many have stated, and I think that it's still a work in progress. One of the main problems is that Pentax hasn't put a lot of effort into guiding its users to get better P-TTL external flash results, IMO. As users, we need to experiment with it a lot and share our findings.

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Old Dec 14, 2007, 11:05 PM   #4
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thanks will give it a try and let you know how it goes
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