Difference in same metering for Tv and Av in Canon 400D

<p>Hi<br>

Last week I was shooting the exterior of a predominantly white building and set the camera to Tv (shutter priority)- shot the scene at 1/125, f/4 at 400 ISO and the building was nicely exposed. I then set the camera to Av (aperture priority), set the f stop to f/4 and shot at 400 ISO and the picture was overexposed. Shouldn't the camera be compensating here when the ISO and the f stop are as before?<br>

Thanks</p>

<p>You were using a tripod and the framing did not change at all between the two shots?</p>

<p>Rob- I didn't use a tripod and my hands are usually steady and the framing was exactly the same. The speed dropped to 1/100</p>

Did you try more than once. Also you might try this question in the Canon or digital camera forums. This isn't really a gear usage forum. You'll probably get more answers there.

<p>1/100 and 1/125th is a third of a stop. It's very possible your framing for metering was not as "exactly the same" as you think, regardless of how steady you are. This could account for the slight discrepancy in shutter speeds.</p>

<p>If you think it is a hardware fault then you should put the camera on a tripod and test it systematically.</p>

 

<p>Spot metering?</p>

<p>why is this in street and doc? wouldnt the Canon forum be more appropriate?</p>

<p>The difference between 1/100 sec and 1/125 sec is small (1/3 of a stop in reality, but this shows the on screen, in viewfinder "adjacent " two default values, I assume). The viewfinder info does not give you the 1/112 sec that were actually used for exposure!</p>

<p>So please look at the more detailed exif files to make sure it was not just the decision difference as to what to display in the viewfinder when the exposure changed - imperceivably from 1/113 and 1/112 sec as the sun turned 1/5th of a degree second between shots. </p>

<p>This would happen, could happen, should happen with any gear, so it is not necessarily a Canon only question.</p>

<p>Thanks Frank - but the shot I got was clearly overexposed (histogram way far to the right) . Could the sun have made that much of a difference in a few seconds? And I was shooting early morning :-)</p>

<p>Yes, the sun's angle changed rapidly during early morning which could account for the difference in exposure. Especially if it was a cloudy day with strong wind.<br>

Like what Frank Uhlig say, the difference in exposure is small enough. But in the cases that you want to nailed it right, I suggest bracketing your shots.</p>