A 5D question....

[^^Gord^^]

I was mulling over the differences between the 30D and the 5D whilst shooting in poor light on Monday / Tuesday. They are basicly the same camera but with the obvious difference of the 5D being full frame and having a higher megapixel count.

I mainly shoot mil aviation at the moment and a lot of it is tricky light but I need to maintain a high shutter speed due to the speed of the aircraft so having a full frame sensor would really help. I can deal with the "loss" of the crop factor by manually cropping into the image and still have a resolution high enough for my needs.

But, my question is about the auto-focus. With the 30D and 5D having the same diamond nine AF system I would expect it to perform better on the 30D as the crop factor of the 30D would mean the plane would fill more of the frame and therefor the AF would be more likely to hit more points of the plane and less likely to miss-focus of something else in the shot.

Would you agree?

Please don't suggest a longer focal length lens to compensate for the crop factor, using the centre point AF or using a 1-series as they are all non-starters.

 

[^^Gord^^]

Ah, interesting. I wasn't aware of the extra AF points. Cheers.

 

[^^Gord^^]

you say the 30D and 5D are virtually identical, I thought the 5D had a bigger body??

Marginally yes it is but I was referring to it's spec rather than physical size.

 

[^^Gord^^]

It doesn't per se but it would allow me to use a lower / usable ISO setting than the 30D in tricky light whilst still getting a high enough shutter speed.

 

[^^Gord^^]

How would it ?

The full frame sized sensor wouldn't need as much time to correctly expose an image compared to the APC (physically smaller) sensor in the 30D. The 5D also has a much better noise control than a 30D so even if you did even us at something like ISO 1000 the amount of noise in the image would be like using a 30D at about ISO 400.

From my experience shooting aircraft you really don't want to go any higher than ISO 800 (ISO 1000 at a push) for a 30D even with noise reduction programs. Aircraft provide a fairly unique shooting situatution as usually need to crop the image, you have a grey jet against a bright sky and you usually have a very limit choice of places to shoot them from. All of these factors mean you can struggle to control noise under certain (i.e. non Summer) lighting conditions.

 

[^^Gord^^]

But on the other hand, since there is inherently less DOF, then you actually need to increase the apiture to get the same DOF had you used a 30D, and so to get a silimar picture you migh actually end up with a slower shutter speed, compared to if you had used a 30D.

Remember, you are using telephoto lenses when shooting jets so DOF really isn't an issue. You will find lots of serious aviation photographers will be using f/2.8 lenses on cropped bodies.

 

[^^Gord^^]

what did you go for in the end gord?

I'm waiting until March to see what Canon come out with. They may come out with something that suits my needs better or they may replace the 5D which should mean I could pick up a 5D for less money