Flash issues with older manual lenses on K10D

DrNick · 03-04-2009, 03:44 PM

I've just got an SMC A 50mm f1.7 and an Auto Chinon 28mm f2.8 lens (which lacks the A setting) for my K10D, and have been playing with them taking photos of the kids this evening, which requires a flash.

I've found that the SMC A lens works well in fully manual mode (M) or flash sync mode (X) with the internal flash on the K10D. The fully manual lens, which would be the equivalent of a Pentax M or K series, does not work so well with the built in flash, and seems to fire on full power at all times. This means that you have to manually adjust the aperture of the lens to balance the exposure and certain combinations of short range and shallow DOF are not achievable.

I do have a Cobra 300D flash that is a TTL unit, and this works fantastically with the manual lens and K10D even down to short range and f2.8

. I just mention this as a word of caution that if any wants to go down the manual lens route, and will need to work with a flash, don't rely on the built in unit, get a TTL unit!

All the best,

Nick.

SOldBear · 03-04-2009, 04:34 PM

Originally posted by DrNick

The fully manual lens, which would be the equivalent of a Pentax M or K series, does not work so well with the built in flash, and seems to fire on full power at all times. This means that you have to manually adjust the aperture of the lens to balance the exposure and certain combinations of short range and shallow DOF are not achievable.

That is correct.

When you need to reduce the power of the built-in flash, you can use a diffuser, as this cheapo one:

Even cheaper is a few layers of napkins.

Quote:

I do have a Cobra 300D flash that is a TTL unit, and this works fantastically with the manual lens and K10D even down to short range and f2.8

. I just mention this as a word of caution that if any wants to go down the manual lens route, and will need to work with a flash, don't rely on the built in unit, get a TTL unit!

I beg to disagree. K10D does not support TTL flash. It requires P-TTL, which is a different animal. I think a TTL flash will fire at full power no matter what lens is attached to the K10D body.

To use the K10D with a manual (pre-PKa) lens, you need a flash with auto setting, and preferrably one with variable output (manual) setting.

DrNick · 03-05-2009, 03:22 PM

Thank you SOldBear, I was a bit too hasty there in thinking the flash was working as a TTL unit.

I tested it again tonight and (although I have not got the manual) I think I had it on auto, as you suggest. It seems it will compensate for the camera to subject distance changing, but the aperture must be set correctly, and if you change it, the picture is then under or over exposed. I also have a Pentax AF200SA, for which I do have the manual, and this only works in fully automatic mode. This does the same thing, so I'm sure you were right, I must have had the Cobra unit on auto, not TTL.

I'm quite happy with the results with both flashes, and I was really motivated to post my first message to share with other newbies my finding that the external Cobra unit worked well with the fully manual lens, whereas the internal unit would not really work easily.

I like your DIY method too though - I guess you have some film bodies as well as digital? I've just got one too, a Pentax Program A which was in the same lot as the lenses and the Cobra flash, and I shot a roll of black and white film just to test it, and had a go at using the darkroom at work to develop it today. People moan about how long it takes, but I'm sure I spend as long on each digital picture in Photoshop as I did in the darkroom today.

All the best,

Nick.

winglik · 03-05-2009, 03:36 PM

When use any not A lens, the flash will be in full power, you have to change aperture to deal with that overpower flash, there is a rule like 36 divides the distance in feet from you to the subject (at ISO 100). so if you are 6 ft always, you have to set aperture to around 5.6 or lower to get a correct image. you can search around here, you should find more detail on using flash on old lens.

03-04-2009, 03:44 PM	#1
DrNick New Member Join Date: Nov 2008 Location: Glossop Photos: Gallery Posts: 6	Flash issues with older manual lenses on K10D I've just got an SMC A 50mm f1.7 and an Auto Chinon 28mm f2.8 lens (which lacks the A setting) for my K10D, and have been playing with them taking photos of the kids this evening, which requires a flash. I've found that the SMC A lens works well in fully manual mode (M) or flash sync mode (X) with the internal flash on the K10D. The fully manual lens, which would be the equivalent of a Pentax M or K series, does not work so well with the built in flash, and seems to fire on full power at all times. This means that you have to manually adjust the aperture of the lens to balance the exposure and certain combinations of short range and shallow DOF are not achievable. I do have a Cobra 300D flash that is a TTL unit, and this works fantastically with the manual lens and K10D even down to short range and f2.8 . I just mention this as a word of caution that if any wants to go down the manual lens route, and will need to work with a flash, don't rely on the built in unit, get a TTL unit! All the best, Nick.

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03-04-2009, 04:34 PM	#2
SOldBear Veteran Member Join Date: Feb 2009 Location: Alameda, CA Posts: 3,206	Originally posted by DrNick The fully manual lens, which would be the equivalent of a Pentax M or K series, does not work so well with the built in flash, and seems to fire on full power at all times. This means that you have to manually adjust the aperture of the lens to balance the exposure and certain combinations of short range and shallow DOF are not achievable. That is correct. When you need to reduce the power of the built-in flash, you can use a diffuser, as this cheapo one: Even cheaper is a few layers of napkins. Quote: I do have a Cobra 300D flash that is a TTL unit, and this works fantastically with the manual lens and K10D even down to short range and f2.8 . I just mention this as a word of caution that if any wants to go down the manual lens route, and will need to work with a flash, don't rely on the built in unit, get a TTL unit! I beg to disagree. K10D does not support TTL flash. It requires P-TTL, which is a different animal. I think a TTL flash will fire at full power no matter what lens is attached to the K10D body. To use the K10D with a manual (pre-PKa) lens, you need a flash with auto setting, and preferrably one with variable output (manual) setting.

03-05-2009, 03:22 PM	#3
DrNick New Member Join Date: Nov 2008 Location: Glossop Photos: Gallery Posts: 6 Original Poster	Thank you SOldBear, I was a bit too hasty there in thinking the flash was working as a TTL unit. I tested it again tonight and (although I have not got the manual) I think I had it on auto, as you suggest. It seems it will compensate for the camera to subject distance changing, but the aperture must be set correctly, and if you change it, the picture is then under or over exposed. I also have a Pentax AF200SA, for which I do have the manual, and this only works in fully automatic mode. This does the same thing, so I'm sure you were right, I must have had the Cobra unit on auto, not TTL. I'm quite happy with the results with both flashes, and I was really motivated to post my first message to share with other newbies my finding that the external Cobra unit worked well with the fully manual lens, whereas the internal unit would not really work easily. I like your DIY method too though - I guess you have some film bodies as well as digital? I've just got one too, a Pentax Program A which was in the same lot as the lenses and the Cobra flash, and I shot a roll of black and white film just to test it, and had a go at using the darkroom at work to develop it today. People moan about how long it takes, but I'm sure I spend as long on each digital picture in Photoshop as I did in the darkroom today. All the best, Nick.

03-05-2009, 03:36 PM	#4
winglik Senior Member Join Date: Oct 2008 Location: NYC Posts: 258	When use any not A lens, the flash will be in full power, you have to change aperture to deal with that overpower flash, there is a rule like 36 divides the distance in feet from you to the subject (at ISO 100). so if you are 6 ft always, you have to set aperture to around 5.6 or lower to get a correct image. you can search around here, you should find more detail on using flash on old lens.