Aperture Priority Underexposure when using Filters

[andrew_buckley1]

I was shooting a college assignment re filters and their effects on black and white film when i noticed an error in exposure.

I shoot with an EOS 1nhs and 28-135mm is lens and was using Cokin P filters. When in Av mode the meter was compensating for the filters as you would expect with TTL metering, however after releasing the shutter and without the meter reading changing, the shutter would be closed after only half the exposure time having elapsed. For instance with a red filter the meter was showing a reading of 15 seconds at f18, but after releasing the shutter it would remain open for 8 seconds only. This appeared to be the case with all filters where a loss of light occurred. However if switching to Manual mode M, the same meter readings would be given and the timed exposure this time would be correct, i.e. the 15 seconds as in the above example. The other way around the problem is to compensate in Av by one stop and this produces the original required exposure time! I have not had a chance to test my other bodies yet to see if the error does replicate itself, but will do so.

Has anyone else had this problem?

Regards

Andrew

[bobatkins]

Were you blocking light from entering the viewfinder at the moment you

released the shutter va the moment when you took the meter reading?

[andrew_buckley1]

After taking meter readings, i closed the eyepiece'shutter' so

readings will not have been altered. The shutter was released via

cable!

Hope this helps.

Regards

Andrew

[howard_dvorin]

Andrew,

[howard_dvorin]

Andrew,

 

<p>

 

I,too, had trouble using a red filter on an EOS 630. I switched to

using a hand held meter and filter factors. Thje results were better.

Howard.