AF performance in low light?

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lowlight

Guest
Hello,

while many aspects are covered in website benchmarks, I have not found a single site who tests AF performance in low light environments.

My EOS 400D is really poor in focusing without the red AF-assist light of the external flash, even with apertures of 1.4 (sigma 30/1.4, canon 50/1.4). The internal flash-burst is not an option (too harsh), and turning off the external flash after AF-lock before shooting is tedious.

I'd like to upgrade to something with a better low light focus, but I'm not sure if the 550D, xxD or 7D are that much better. Nikons (300, 300s) and the EOS 1000D (not an option) do have a built-in AF-assist lights, another option would be the ST-2E transmitter (quite expensive red light...). Or a custom function to use only the AF-assist beam of the EX 430 but not the flash.

Did someone test low light AF performance on EOS bodies?
 
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that1guy

Guest
I don't really know of anyone who tests that in any kind of a scientific way, but I do know that The Digital Picture will sometimes mention AF speed in their reviews of Canon cameras. Reading his reviews has helped me get a better idea of how the various Canon cameras focus compared to each other. It doesn't give you a way to compare to other brands, but it might be helpful to you if you are just shopping Canon (it was to me). Here is a link to the site: http://www.the-digital-picture.com/
 
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that1guy

Guest
Oh, and from what I understand, I think you might be very pleased with the AF on the 7D. Haven't tried it myself, but I have heard it is outstanding.

One more idea...is it possible for you to rent equipment? That could be a good way to try some stuff out as well.
 
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slr_noob

Guest
You can always rent one for say a week and see how you like it. On a note, a large aperture lens has nothing to do with low-light AF performance. It will make certain point (usually the center point) more sensitive.

I moved up from a XSi/450, which its AF system is similar to 400D/XTi, to a 7D. I am very happy with its overall AF speed performance. All AF points are cross-type (sensitive to horizontal and vertical details), which is a plus regardless of lighting situations, and I ran into a situation where my 450D failed to focus even though it's in the middle of the day. It won't take long before you like the responsiveness of the AF system.

Focusing in available light is great too. I once shot a small event in a dimly-lit bar. It may not focus as quick as if you're outside in the middle of the day, but certainly not likely to hunt unless the area you're focusing on an area that has not enough contrast for the AF to pick up.

Just a reminder, this camera has some learning curve. One thing I recommend is to choose your focal points instead of letting the body choose. I used to do the other way around and thought I had some bad AF issues for the first week I had it. Now it's so much better.
 
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DetlevCM

Guest
lowlight said:
Hello,

while many aspects are covered in website benchmarks, I have not found a single site who tests AF performance in low light environments.

My EOS 400D is really poor in focusing without the red AF-assist light of the external flash, even with apertures of 1.4 (sigma 30/1.4, canon 50/1.4). The internal flash-burst is not an option (too harsh), and turning off the external flash after AF-lock before shooting is tedious.

I'd like to upgrade to something with a better low light focus, but I'm not sure if the 550D, xxD or 7D are that much better. Nikons (300, 300s) and the EOS 1000D (not an option) do have a built-in AF-assist lights, another option would be the ST-2E transmitter (quite expensive red light...). Or a custom function to use only the AF-assist beam of the EX 430 but not the flash.

Did someone test low light AF performance on EOS bodies?
400D - that's what I used to use...

Its AF isn't brilliant but not too bad at all.

My guess is you are focussing on a low contrast area - which are easy to find in low light situations.
No matter which camera you have you need contrast to focus - if there is no contrast it will not focus porperly.

Now some cameras are better at locking in in worse conditions than others - and the 400D isn't the low light camera, but I'd beware of just going and buying new equipment.

You might also want to join here? http://photography-on-the.net/forum/index.php

Now, if you really feel you need better AF - the 7D is possibly the most future proof and best choice. A better camera will also be the much cheaper 550D - but is it worth the money - difficult to decide.