PentaxForums.com - View Single Post

snostorm · 01-07-2007, 10:56 PM

Originally Posted by Mo

Yup...

According to page 153 of the manual, the external flash attempts TTL with M and K lenses. Incorrect exposure may occur near min/max aperture values.

Since the camera itself has no TTL sensor, the built-in flash is useless on M and K lenses (unless you're lucky)!

Despite all this techncal talk, some combinations may still work

Hi Guys,

I don't know where you're getting this -- page 153 of the manual clearly states that the DS is indeed TTL capable, but it's "restricted" (that's what the "#" means) to ISO 200-400. Wide apertures may cause overexposure and narrow ones undereposure. Why would they even list all the TTL flashes in the manual if they couldn't be used with the DS?

These restrictions and caveats (and cost, of course) were probably why Pentax dropped TTL support in the K series bodies. The problem is that reading off the CCD has been found to be not as accurate as it was with film (The reflectance is different, hence the restriction in ISO and the caveats concerning exposure at the ends of the aperture range). It was obviously good enough for a lot DS owners to be very disappointed that the support wasn't continued in the K10D (including me).

I have a DS and regularly use an AF 200T, an AF 280T and an AF 500 FTZ with it using TTL -- and hundreds of shots under various conditions, shutter speeds, and apertures to prove that it's not just luck.

The onboard flash doesn't work with K and M lenses because it's P-TTL only and apparently needs the aperture information to meter. Whether the body has a TTL meter or not is not the cause.

BTW, Matjazz -- the D and DS (and i'm not sure about the DS2) are the only Pentax DSLRs that support TTL flash.

01-07-2007, 10:56 PM	#8
snostorm Senior Member Location: Chicago suburb, IL, USA Gallery Photos: 0 Posts: 130	The DS is indeed TTL compatible Originally Posted by Mo Yup... According to page 153 of the manual, the external flash attempts TTL with M and K lenses. Incorrect exposure may occur near min/max aperture values. Since the camera itself has no TTL sensor, the built-in flash is useless on M and K lenses (unless you're lucky)! Despite all this techncal talk, some combinations may still work Hi Guys, I don't know where you're getting this -- page 153 of the manual clearly states that the DS is indeed TTL capable, but it's "restricted" (that's what the "#" means) to ISO 200-400. Wide apertures may cause overexposure and narrow ones undereposure. Why would they even list all the TTL flashes in the manual if they couldn't be used with the DS? These restrictions and caveats (and cost, of course) were probably why Pentax dropped TTL support in the K series bodies. The problem is that reading off the CCD has been found to be not as accurate as it was with film (The reflectance is different, hence the restriction in ISO and the caveats concerning exposure at the ends of the aperture range). It was obviously good enough for a lot DS owners to be very disappointed that the support wasn't continued in the K10D (including me). I have a DS and regularly use an AF 200T, an AF 280T and an AF 500 FTZ with it using TTL -- and hundreds of shots under various conditions, shutter speeds, and apertures to prove that it's not just luck. The onboard flash doesn't work with K and M lenses because it's P-TTL only and apparently needs the aperture information to meter. Whether the body has a TTL meter or not is not the cause. BTW, Matjazz -- the D and DS (and i'm not sure about the DS2) are the only Pentax DSLRs that support TTL flash.