Originally posted by njpentax Thanks for the responses. I guess I will be eliminating my non-a lenses. I've started accumulating various lenses that are duplicates. I'd like to have a collection of A type so I don't have to fool with the stop down and manual exposure as well as the flash issues.
You don't need to stop getting Non A lenses to use flash.
There are 3 ways you can still use flash with Non A lenses.
1) Pick up a used *istD, DS, or DS2. All of these bodies support both TTL and P-TTL flash. Let me explain the difference.
TTL flash has a sensor that reads light reflected off the film (the bad old days) or sensor (digital) and controls the duration of the flash directly by the light reflected off the recording surface.
P-TTL (and I wont go into what the P stands for) does not read the light produced by the flash during exposure at all. P-TTL uses the camera's metering and sends a preflash out to read the light reflected back from the flash and the uses the cameras normal metering to measure the light from the flash, plus background ambient. It then calculates the flash duration required, knowing the shooting exposure (shutter, aperture and ISO, existing light) and when the shutter opens, it produces a flash duration to meet the exposure requirements. THe P is for Predictive, Pre flash, Pentax or what ever you pick.
The problem with P-TTL and older lenses is that it does not know the difference between the wide open aperture (when focusing etc) and the shooting aperture, so the camera shoots the flash at full power. TTL has a problem that has been around since the beginning of potential over exposure if if there is a lot of background light, because even though theflash stops the shutter is still open gathering light. But TTL, since it reads directly the light hitting the sensor from a flash, can meter with old lenses because it is the real light during exposure it is measuring.
2) the second method is to purchase a flash that supports AUTO flash, where the flash itself has a sensor, to control duration. The AF540FGZ is one such flash, and can work in auto mode.
3) learn manual flash calculations, and adjust aperture and flash power (if possible) based on ISO, shooting distance, and flash power to get the correct exposure. After All, that is how it was done in the beginning