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08-28-2009, 08:44 AM   #1
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Just Got My AF540GZ Today

As the title says, i've read the manual, personally I think the manual could do with some improvements.

Some things I don't quite get:

1. I don't get the auto & manual modes. In auto you have control over ISO & apperture yet in manual you can only dial 1/1, 1/8...1/64 etc. I was taking shots using a fully manual 50mm and found the auto mode gave the best results.

2. Wireless P-TTL, I figured out how to use it, suprisingly works a treat however is the zoom when set auto supposed to adjust like it does when the flash is attached to the camera?

Any other help would be really appreciated, so far I'm loving this flash just trying to understand it.


FYI bought it from pro digital, it was delivered from Canada on the 25/8 and I picked it up today in Melbourne, very happy with the speed of delivery.

08-28-2009, 10:52 AM   #2
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QuoteOriginally posted by C.W Tsorotes Quote
1. I don't get the auto & manual modes. In auto you have control over ISO & apperture yet in manual you can only dial 1/1, 1/8...1/64 etc. I was taking shots using a fully manual 50mm and found the auto mode gave the best results.
I'm not sure what you "don't get." In flash auto mode, you match the ISO and the aperture settings on the flash and on the camera body. The flash uses its own light sensor to determine how much light to output.

In manual, you have full control of how much light (full, half, quarter, ....) to output.

QuoteOriginally posted by C.W Tsorotes Quote
2. Wireless P-TTL, I figured out how to use it, suprisingly works a treat however is the zoom when set auto supposed to adjust like it does when the flash is attached to the camera?
That's by design. In wireless mode, the camera (and the lens of course) is at one location while the flash unit is at another. There is no guarantee that the field of the lens matches that of the flash head. You yourself have to determine the field of the flash and adjust the zoom level accordingly.
08-28-2009, 11:52 AM   #3
DAZ
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I sense a limit in the knowledge on what the different modes are that is limiting the use of these modes so maybe a short description will help.

Starting with the simplest is manual. In manual all you are telling the flash is how much power to flash at. 1/1 is full power. ½ is half power or 1 stop down. ¼ is of course ¼ power and 2 stops less. This just keeps going to the minimum setting. This is just like on the camera in that you can set the setting you the photographer want so you can get just what you want with out some automatic setting fighting you. This also means that nothing stop you from messing things up so you have to understand what it is you are doing. This mode should work with any camera you have manual control and can trigger a flash. This may explain your less the satisfied out put with this mode. For some this is about the only mode they use.

Next is Auto. With this mode you tell the flash some things it needs to know in order for it to calculate the proper exposure. The things it needs from the camera are ISO/aperture and from you the approximant dissents to subject. With this when the camera triggers the flash the light from the flash will reflect off the subject (or what ever is in front of the flash that reflects the most light). A sensor on the flash will detect this light and turns off the flash when the flash thinks there is the correct amount of light that it has calculated from the information you gave it for the proper exposure. The things to remember about Auto are GIGO (Garbage In Garbage Out). If you tell it the wrong things you get the wrong things out. It is the light coming back to the flash and this may or may not be from the subject. If there is a white wall or window 10 feet behind the subject this kind of thing can fool the flash into thinking it has all the light it needs so you get a dark subject. The last thing is it is all from the point of view of the flash. If the flash is on camera this is about the same but if it is off camera this can be extremely different.

Last is P-TTL. With this the camera tells the flash just about every thing. The camera knows its settings. It tells the flash how much zoom to use (if it is on camera but if it is not on the camera this is the one thing you have to tell the flash is because it has no way to know this). Has the unit trigger a low power pre-flash. This goes out to what is in front of the flash. It then reflects back to the camera though the lens (this is the TTL part) to the sensors the camera uses to calculate proper exposure. It uses this information to tell the flash unit how much light to put out. There is a subtle different here besides the TTL part and what sensor is used. First in Auto the unit is told when to stop putting out light but in P-TTL the unit just puts out the amount of light as instructed. This means if the light changes from the pre-flash (like some other flash at the same time as the pre-flash) this can mess things up. With Auto it is just more light the unit doesn’t need to put out so it turn off sooner. If flash unit is close to the subject but the camera is much further away in Auto the flash could think there is enough light and turn off to soon but from the cameras point of view it is may not be enough. The last it is what the camera sees not what the flash sees. So if the white wall is behind the subject from the flash units point of view but not the cameras point of view then the wall is not fooling the sensor.

Basically what SoldBear said. He is much more concise.

DAZ
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