Steve, it's actually more prerrable to use Tv (shutter priority mode) & use EXP LOCK (Exposure Lock) for manual adjustments to the iris.

Using Aperture mode puts auto shutter active & my guess is the shutter was adjusting... changing the exposure you thought you had as you zoomed out.

Just a thought
Bill

Tv Mode
 

Hi Bill, thanks for the response.

I will try Tv mode and exposure lock next time.

The strange thing about this was that i wasn't zooming when the aperture was adjusting and I double checked to see if I was in Av mode. The camera actually ticked down through increments of the iris until it got to a point where the window light was exposed "properly." It wasnt a smooth transition even. I haven't had a chance to look a the footage so I can't say I captured what I saw. I put the camera in Av mode, framed the shot, adjusted the aperture to overexpose the window and as i was getting ready to hit the record button and start my zoom, I stood watching the iris close down. Not what I expected. Tomorrow i will look at the tape.
Thanks again, Steve

Hi Steve. The camera is just trying to do its job - i.e. adjust to what it thinks is the correct exposure. If you want a deliberately overexposed area, you need to select manual mode or else press exposure lock and then adjust the iris accordingly.

By the way, I would not use Av mode because this causes the shutter speed to jump around and affects the smoothness of motion on the shot. If you want an auto mode with some control, Tv mode is more useful.

Richard

Hi Richard, I guess all I have to say is "duh" I wasn't thinking in terms of still cameras where if you set the aperture to a fixed setting the shutterspeed changes. Which is what is happening with this camera. The A1 is speeding up the shutter speed in increments to adjust for the wide open iris. A still camera with moving pictures. Bill said this and it was late last night when I was reading his posts so I didn't get it.

thank you. Your explanation clarified this process. Next time I am in the situation, I will try Bill's and your suggestion to use exposure lock. I considered it but one of the people I was with was getting antsy to leave and there was more to see and capture.
Steve