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Canon Exposure Problem
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MattJeff
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Dec 23, 2006, 11:37 PM
 
i have the Canon Rebel xt, i can change my apature up to 30 and down to 2.6 but somethimes it will only let me go to 5.6 or 22, ect...why is that?
     
Dark_Lotus
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Dec 24, 2006, 01:56 AM
 
Originally Posted by MattJeff View Post
i have the Canon Rebel xt, i can change my apature up to 30 and down to 2.6 but somethimes it will only let me go to 5.6 or 22, ect...why is that?
Someone correct me if I'm wrong but it might be because you do not have it set to full manual controls, my camera has four different modes, full manual, full auto, just manual shutter, and just manual aperture.
     
MattJeff  (op)
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Dec 24, 2006, 03:11 AM
 
hmmm i thought you could only change it under manual, is there a "Full manual" that im not seeing? its the xt not the xti if that changes it
     
Demonhood
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Dec 24, 2006, 05:22 PM
 
lenses have maximum apertures (the smaller the better). zoom lenses sometimes have a range that changes. so a 70-200mm lens could be a ƒ3.5 at 70mm but ƒ5 at 200mm.

if this still doesn't address your problem, let me know and i'll splinter these last few posts off into a new thread.
( Last edited by Demonhood; Dec 24, 2006 at 05:31 PM. )
     
MattJeff  (op)
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Dec 26, 2006, 02:39 AM
 
dont worry about it its not that big of a prob. thanks tho
     
Synotic
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Jan 12, 2007, 05:06 PM
 
This is probably too late, but there are conditions under which the light us either too great or too little to create a "correct" exposure. Depending on what mode your in, your camera won't let you create too small or too wide an aperture. Shooting at bright lights? Your camera might not let you open the aperture wide enough. Shooting in the dark? Then f/22 might not be the best best choice. I also think your focus can affect which aperture you can choose, but someone can correct me on that.
     
keekeeree
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Jan 13, 2007, 05:52 PM
 
Originally Posted by Synotic View Post
This is probably too late, but there are conditions under which the light us either too great or too little to create a "correct" exposure. Depending on what mode your in, your camera won't let you create too small or too wide an aperture. Shooting at bright lights? Your camera might not let you open the aperture wide enough. Shooting in the dark? Then f/22 might not be the best best choice. I also think your focus can affect which aperture you can choose, but someone can correct me on that.
Nope, focus has no affect on which aperture you can choose.
     
austincabot
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Jan 16, 2007, 04:43 PM
 
Originally Posted by Demonhood View Post
lenses have maximum apertures (the smaller the better). zoom lenses sometimes have a range that changes. so a 70-200mm lens could be a ƒ3.5 at 70mm but ƒ5 at 200mm.

if this still doesn't address your problem, let me know and i'll splinter these last few posts off into a new thread.
This is correct. However, lens have different maximum apertures at different focal lengths. For instance, the maximum aperture on my 18-55 kit lens at 18mm is 3.5, but at 55mm it is 5.6.

Edit - I just realized that what I said was already addressed - sorry.
     
Goldfinger
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Jan 17, 2007, 08:15 AM
 
Originally Posted by keekeeree View Post
Nope, focus has no affect on which aperture you can choose.
Unless you're using a Macro lens...

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keekeeree
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Jan 17, 2007, 02:39 PM
 
Originally Posted by Goldfinger View Post
Unless you're using a Macro lens...
Why is using a macro lens different from other SLR lenses and how they allow you which aperture you can (not should...that's a different discussion altogether) choose?
     
Goldfinger
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Jan 17, 2007, 03:32 PM
 
The closer you go (focus) with a macro lens the shallower your depth of field gets, no ? Because the lens moves away from the film (or sensor) you change your effective maximum aperture, for example your 2.8 becomes a 5.6 at 1:1.

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