Also, if using flash, the ISO need not be set at 1600 because of low light situation. You are providing a high light situation with the flash. using your post #3 hypothetical you could easily use ISO 100
The 1/50 isn't too low a shutter speed for hand holding unless you use a telephoto lens. With flash and if the ambient light is low then the shutter speed won't make a different as the entire exposure is done with the flash that has short duration. The 1/50 is the fastest shutter speed to use with flash on the M6. You can use slower shutter speed if you wish. At ISO 1600 which is very fast film the ambient light would play a rather important role.
Your ability to link will be limited on APUG until you have been around a bit longer and made a few more posts. That was instituted to help stop the robo-spammers.
Originally Posted by roberttalbot
TTL doesn't read distance. It just measures how much light from the flash has bounced back from the subject. When enough has bounced back to properly expose the film, it turns off the flash.
The distance affects how much light from the flash reaches the subject and how much light bouncing from the subject reaches the camera - if you are far away the light spreads out more.
Are you using the flash as your source of light, in situations where there isn't enough ambient light to work? If so, the TTL flash will work great.
If you are trying to use TTL flash to "fill" or balance lighting in situations where there already is enough light to expose the film, you will most likely just get frustrated. The focal plane shutter on the camera limits your flash use to speeds of 1/50 second or slower. This means that apertures need to be small and/or films need to be slow in order to expose properly for ambient light. If you do that though, the flash will often need to be too close to the subject.
In addition, the ambient light will tend to confuse the TTL metering, and cause the flash to shut off prematurely.
If you are going to use fill flash with a camera that requires a 1/50 second shutter speed for flash, most often you need to use the flash in a fixed position, in manual mode, using either a guide number calculation or a flash meter.
Originally Posted by cowanw
The only reason to use ISO 1600 is if that is the film you have. If you are choosing a film for use with flash, I'd recommend a slower film.