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Thread started 03 Dec 2011 (Saturday) 12:14
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Help? Trouble with changing Aperture on 40D

 
Siberius
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Dec 03, 2011 12:14 |  #1

Hey all,

I'm sure I am missing something here but I can't work out what it is. Probably just a gap in my knowledge. Maybe you can tell me what's up.

Ok, so I find sometimes that if I am in AV mode I can set my aperture anywhere up and down the scale from say 4 up to 22. No problem.

But then when I switch to M mode, it sticks it at 11 and will only let me adjust shutter speed. An example of what I was doing was the other day, taking a relatively close up shot of something and I wanted to maximise depth of field, but when doing that on AV mode, it was badly underexposing. So my plan was to set to M mode, stick it up on 22 and then adjust my shutter speed to expose right, but as I say, it refused to move off the one setting. I gave up and used 11 in the end and just took 2 pics, one for the front of the object, another for the back, then merged them. Obviously that's not ideal.

So what am I missing here? I know lenses have a max and min aperture, but I don't know what would make the camera want to stick in the middle.

Thanks for any help you can give.




  
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snyderman
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Dec 03, 2011 12:20 |  #2

Might want to start with the easy stuff. Turn camera off, remove battery, reinstall, turn on camera. Fixed? If not, the contacts on your lens or camera might be dirty. There is a method for this, that I better not explain for fear of steering you wrong. Also, you might want to put your camera in full auto mode and see where the aperture setting move to. These are a few potential free fixes.

Like many things, it's probably something simple.

dave


Canon 5D2 > 35L-85L-135L

  
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amfoto1
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Dec 03, 2011 13:11 |  #3

Actually there might be an even simpler solution....

Do you have the off/on switch of the camera set to the third "hockey stick" position? You need to use that and the quick control dial on the back of the camera to change the aperture, while using the main dial up by the shutter release to change the shutter speed. (There is a custom function in some of the Canon models that allows you to swap the function of these two dials and/or to reverse their direction.)

If you just set the camera to "on", then the rear dial (aka quick dial) is disabled and won't change things.

This is also true if using one of the auto exposure modes... where the rear/quick dial serves to set Exposure Compensation. You have to have the off/on switch in the third position to allow that dial to work while in shooting modes (it will still work in the image playback modes).

I don't necessarily recommend using f22. With the high density of digital sensors, there's a problem with small apertures called "diffraction" that occurs when using small lens apertures. It sort of softens the image and there's a loss of fine detail at the smaller apertures. If I recall correctly, on the 10MP 40D the "diffraction limited aperture" is f10... smaller than that and diffraction begins to occur. It will probably be minor and unnoticable at f11, perhaps even f16 woudl be usable, but might be getting pretty strong at f22.

Set a lower ISO, rather than using a super small aperture. And, yes, a higher shutter speed will work, too...

But if trying to use a particularly slow shutter speed in fairly bright light, a smaller aperture (f11, f16) and the lowest ISO setting (100) might not be enough. In that case, you might need a good quality Neutral Density filter to further reduce the light reaching the camera's sensor. These come in various strengths reducing one stop, two stops, 3 stops, 5 or 6 stops, even 9 or 10 stops of light. (often stated 0.30 for one stop, 0.60 for two, 0.90 for three, etc.). A good quality filter will be very neutral gray so it doesn't add any color tint to an image. I'd recommend a multicoated filters, such as the B+W MRC here (external link).

In M mode, you should use the camera's meter readout scale on the top LCD or shown in the viewfinder... adjust your combination of settings (ISO, shutter speed and aperture) until the indicator is centered. Alternatively, you can use a separate handheld meter to determine your settings. Or in many common lighting conditions simply learn to set them by eye (Sunny 16 Rule). Note that when using any of the Auto Exposure modes (Av, Tv, P) the scale on the top LCD or in the viewfinder serves to indicate Exposure Compensation, not the same meter readout shown in M mode.


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Veemac
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Dec 03, 2011 13:15 |  #4

amfoto1 wrote in post #13489402 (external link)
Actually there might be an even simpler solution....

Do you have the off/on switch of the camera set to the third "hockey stick" position? You need to use that and the quick control dial on the back of the camera to change the aperture, while using the main dial up by the shutter release to change the shutter speed. (There is a custom function in some of the Canon models that allows you to swap the function of these two dials and/or to reverse their direction.)

If you just set the camera to "on", then the rear dial (aka quick dial) is disabled and won't change things.

That's also true if using one of the auto exposure modes,

^This was my first thought as I read the OP.


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David ­ Ransley
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Dec 03, 2011 16:16 |  #5

Yes, if you switch it on - go further - one more click. Then the dial is active.


DRH

  
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Siberius
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Dec 04, 2011 08:46 |  #6

Hey guys,

I just wanted to pop back in and thank you for your help. What bugs me is that I should have known this... I knew there was a good reason to always have it switched to that second line, but over time forgot what it was.

At least now, I will have a much harder time forgetting eh?

Thanks again for your input and time, especially the additional info from amfoto. I might do a bit of testing to see what I can get away with small aperture wise as I definitely want as big a depth of field as possible on those close up shots, but now I can try a few out and see what is acceptable, with the knowledge if it starts looking bad of why it's looking bad. Another thread answered before it began there perhaps!




  
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Help? Trouble with changing Aperture on 40D
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