Poor metering on Rebel XTi

jamesino

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When shooting indoor photography with flash at ISO 100 with a Canon Rebel XTi and the kit lens in aperture-priority mode, I've noticed that the camera always selects a shutter speed that is too slow. At times when the camera selects 1/4 of a second, 1/200 of a second looks just fine and properly exposed. Does anyone else notice this?
 

Sideburns

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1/200 with a kit lens indoors? Are you smoking crack/ have amazing lights/ have glass ceilings and walls on a sunny day?

Seems a little fast to me...
It also depends on where you're metering from and what method you're using.

What's the 1/4 second exposure look like?
 
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jamesino

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The 1/4 and the 1/200 exposure looks pretty much the same in terms of brightness. The 1/4 has a slight yellow (the colour of my light) and white (flash) shift because the exposure lasts longer than the duration of the flash and I was unable to hold it completely still.

I've actually got just 2 incandescent light bulbs.
 

Sideburns

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If they look the same...then you're not shooting in aperture priority mode...because that doesn't really make any sense.
*shrugs*
Perhaps I'm missing something.
 

table1349

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When shooting indoor photography with flash at ISO 100 with a Canon Rebel XTi and the kit lens in aperture-priority mode, I've noticed that the camera always selects a shutter speed that is too slow. At times when the camera selects 1/4 of a second, 1/200 of a second looks just fine and properly exposed. Does anyone else notice this?

That is because in AV mode the flash unit is acting as fill light and giving you very slow shutter speeds. If you are using flash shoot manual, set the aperture to what you want and the shutter speed to 125. Let the flash then adjust to the situation as far as power is concerned.

Great reading on everything you need to know about using EOS flash.

http://photonotes.org/articles/eos-flash/
 

iriairi

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That is because in AV mode the flash unit is acting as fill light and giving you very slow shutter speeds. If you are using flash shoot manual, set the aperture to what you want and the shutter speed to 125. Let the flash then adjust to the situation as far as power is concerned.

Great reading on everything you need to know about using EOS flash.

http://photonotes.org/articles/eos-flash/

~~~

Thanks for the link. It helps confirm some of the things I have been struggling with.
 
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jamesino

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Thanks, I read that article.
So basically, in P mode, the meter is trying to expose the subject properly, while in Tv and Av modes, the meter is trying to expose the background properly?

And when the camera exposes in Fill-flash mode, it basically ignores the fact that you have flash on and goes on to meter the background to correctly expose the bg right?
 

table1349

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Thanks, I read that article.
So basically, in P mode, the meter is trying to expose the subject properly, while in Tv and Av modes, the meter is trying to expose the background properly?

And when the camera exposes in Fill-flash mode, it basically ignores the fact that you have flash on and goes on to meter the background to correctly expose the bg right?

NO, Per the tutorial. Answer to FAQ 10.

[FONT=Verdana, Arial, Helvetica, sans-serif][SIZE=-1]"Av (aperture priority) and Tv (shutter speed priority) modes set the shutter speed or aperture to expose for the existing light conditions correctly. They then fill in the foreground using flash. If light levels are low you will need a tripod to avoid blur."

It's metering the whole shot to fill in the foreground correctly.
[/SIZE][/FONT]
 
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jamesino

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Oh so the intensity of the flash can be different?
 

usayit

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Yes...

As Gryph posted... Av and Tv modes meter existing light conditions (just like normal) and the flash's power (I think this is what you mean as "intensity") is pulled back for fill.
 
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jamesino

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Sorry for the naiveté: so in fill mode, the flash is less "powerful" than in normal illumination mode? Are there any other differences between the 2 flash modes?
 

table1349

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Sorry for the naiveté: so in fill mode, the flash is less "powerful" than in normal illumination mode? Are there any other differences between the 2 flash modes?

Welcome to the wild, wonderful world of additional light source photography. There are several differences. The best answer to your questions at this point would be to completely read all the information from the link I posted. Great source for Canon. Once you get through all of it, a lot of things will start to click into place.

As you venture further into this new and exciting world, be prepared for surprises, disapointments, startling successes and the learning of a whole new vocabulary of curse words. :lol::lmao::lol::lmao: That's the way it goes!!!!:confused::lol:
But once you get your feet on the ground a little bit you will be amazed at how easy it can become to get that effect you want.

Lighting can be tricky, but a little reading and a little practice will teach you a worlds worth of information on what you can do with your equipment. Have fun.

Here is a good source on lighting techniques.
http://strobist.blogspot.com/
 

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