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Aperture problems? (Canon T2i)

post #1 of 6
Thread Starter 
I always had a hunch that there could be something wrong with my T2i. Whenever I tried to adjust my f-stop, I noticed that the aperture opening would stay the same size, no matter what setting it was on.

So I decided to do a DOF test, same one as this one. Fast forward to 45 seconds please.

[ame]http://www.youtube.com/watch?v=gXhy9WnY7UA&t=0m45s[/ame]

So the DOF here at f/5.0 should be limited while a bigger f/stop should have a better DOF. This isn't the case with my camera.

The only thing that happens when I change the AV is that the screen gets darker as I raise the aperture (I know this should be a good sign).

I tried switching to my EF-S 55-250mm lens and same thing.

So is there a problem?
Edited by youra6 - 8/20/11 at 5:26pm
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post #2 of 6
The aperture blades don't close down until you press the shutter unless you press the DOF preview button.

Try the test again. Try 55mm f/5.6 and then again at something like f/22. There should be a large difference in DOF. Stabilize the camera so you don't have to crank up the ISO or worry about shutter speed during the test.

I see in the video he's using live view. Are you just doing that or are you taking pictures that appear to be something other than you were expecting?
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post #3 of 6
Thread Starter 
Quote:
Originally Posted by ljason8eg;14657317 
The aperture blades don't close down until you press the shutter unless you press the DOF preview button.

Try the test again. Try 55mm f/5.6 and then again at something like f/22. There should be a large difference in DOF. Stabilize the camera so you don't have to crank up the ISO or worry about shutter speed during the test.

I see in the video he's using live view. Are you just doing that or are you taking pictures that appear to be something other than you were expecting?

I used the DOF preview and yes the blades do adjust. I'll ty and lower the exposure time to like 2 seconds so I can see the blades close.

I took a couple of pictures and the DOF does change based on the aperture size. I did the test without using Live View, so that's why I was a little confused.

Thanks!
Edited by youra6 - 8/20/11 at 5:47pm
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post #4 of 6
Quote:
Originally Posted by ljason8eg;14657317 
The aperture blades don't close down until you press the shutter unless you press the DOF preview button.

^^ This

If you really have doubts about your equipment you can test in a few other ways:

Set to Av.

Mount camera on tripod and shoot the same scene three times at f2.8 (or as wide open as you can), f8, and f22.
Check your EXIF data. Your shutter speed should be inversely proportional to the aperture.

...or..

If you want to test DoF, put your camera on a tripod and angle down 45 degrees. Lay a yardstick in line with your FoV. Go to manual focus and put the 18 inch mark in your center focal point. Shoot in Av at the above settings and compare DoF using markings on yardstick.

TBH, if your aperture blades were stuck, you would notice immediately because of incorrectly exposed shots.

Just my 2c worth...hope it helps,

Rich

Edit: I type too slow...tongue.gif
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post #5 of 6
You can also point the lens toward you and watch the aperture blades move through the front element as you push the DOF preview button.
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post #6 of 6
Quote:
Originally Posted by youra6;14657075 
I always had a hunch that there could be something wrong with my T2i. Whenever I tried to adjust my f-stop, I noticed that the aperture opening would stay the same size, no matter what setting it was on.

So I decided to do a DOF test, same one as this one. Fast forward to 45 seconds please.

http://www.youtube.com/watch?v=gXhy9WnY7UA&t=0m45s

So the DOF here at f/5.0 should be limited while a bigger f/stop should have a better DOF. This isn't the case with my camera.

The only thing that happens when I change the AV is that the screen gets darker as I raise the aperture (I know this should be a good sign).

I tried switching to my EF-S 55-250mm lens and same thing.

So is there a problem?


What exactly are you shooting? The further your subject is from you, the greater your DoF is going to be at any aperture.

You can get an idea of DoF numbers for different Apertures and subject distances here.
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