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12-29-2012, 03:27 PM   #1
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AF540 questions

Hi, just picked up an AF540, until now I've used a vivitar that did not support P-TTL. Always used manual. Now I've been experimenting with the 540 and P-TTL. With my K5 set to manual and if I have my shutter at 1/90th of a second and shoot a sequence of pictures changing my aperture setting say from 2.8 to 4.5 to 8.0 to 22 ETC shouldn't the 540 track this and increase the power so that all the shots are exposed consistently? It does not, once I hit 8.0 and up each picture is considerably more under exposed. I've tried changing the K5 from manual to AV mode but the results are the same. Also, a second question, when I am using the 540 in manual mode and I shoot a sequence of pictures each time decreasing the power of the 540 from 1/1 to 1/2 and so forth down to 1/64th my exposure is consistent and the guide always indicates a distance of 20 feet. Am I so lame as to not understand some basic principles? I have read booth manuals and a bunch of stuff online and still I am totally confused. Any suggestions would be appreciated. Thanks in advance

12-29-2012, 03:41 PM   #2
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Does the flash by any chance fire at full power when at f/8 and above? That would explain things.
I don't know about the guide.
12-29-2012, 03:48 PM   #3
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I don't know. I thought P-TTL would adjust the flash accordingly. So if I'm set at 8.0 as opposed to 4.5 shouldn't the flashes power increase?
12-29-2012, 04:26 PM   #4
Ole
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Page 60 in my manual indicates that P-TTL is not available in M exposure mode.

The manual isn't well written and my interpretation could be wrong.

12-29-2012, 09:31 PM   #5
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yes, that's exactly what my scale reads, now the problem is this, if I shoot a picture at f22 about 1.75 meters from my subject it is exposed in a certain way, now I change my aperture value to 2.8 my scale now indicates I should be about 20 meters away, but i do not change the distance to my subject, so I am still 1.75 meters away and my subject is exposed exactly the same as when my aperture was at f22. I would think at f2.8 at 1.75 meters I should be so over exposed it should blow it out. I wonder if something is wrong
12-30-2012, 12:26 AM   #6
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Yes, but it can't go above //full power//. Start with the flash at 1/64 and adjust ISO/aperture until you get a good exposure. Then lower the ISO one stop and set the flash to 1/32. This should produce a similar exposure. Continue doing this until you hit 1/1 with the flash.
ex. flash 1/64 ISO 3200 f/16
next flash 1/32 ISO 1600 f/16
next flash 1/16 ISO 800 f/16
etc.
etc.

EDIT Wow, beaten by 4 posts.
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