10D question and hyperfocal questions

[petiot]

Hi

I bouhgt a 10D few days ago, and i have a question: i have noticed that in evaluative mode (icon with the square, bracket and dot : [(0)]) and when a AF point is manually selected, the camera expose for the subject behind the selected AF point.
If i understand well, evaluative mode is used to expose at an average of the whole picture. Does it mean that it is impossible to use evaluative mode when one AF point is manually selected?

An other question about Hyperfocal this time. I found a very good web page that generates hyperfocal table (http://www.johnhendry.com/gadget/hf.php). However, because of the 10D 1.6 focal multiplier i am not sure if i have to use the 24 mm (i have a EF24-85 mm lens) or the 24*1.6 to build the hyperfocal table for the 10D.

any help is welcome

thank you

Dan

[Longwatcher]

I may be wrong, but since the 1.6x is trully a cropping factor and the lens has not changed in relation to the focal plane, you should use the value for the lens.

That said, since I messed up my memory on hyperfocal, I wouldn't necessarily trust my answer.

[hmhm]

petiot wrote:
...If i understand well, evaluative mode is used to expose at an average of the whole picture...


Evaluative mode isn't just averaging over the whole frame, it is trying to be "smart". It splits the view into 35 zones, it considers the focusing point to try to determine the subject, considers the camera's orientation, and (in theory) compares the results to some database for classification of the image. Based on how it is described, it would be hard to predict exactly what it would do in any given situation, but it seems to be trying to figure out what's the subject, what's the background, etc.

petiot wrote:
...However, because of the 10D 1.6 focal multiplier i am not sure if i have to use the 24 mm (i have a EF24-85 mm lens) or the 24*1.6 to build the hyperfocal table for the 10D.
...


Use the "real" focal length, not the multiplied focal length, but divide the circle of confusion by 1.6 relative to 35mm film. Most DoF calculators provide a "custom" field for CoC, as an alternative to picking one of the film formats. Most people use .033-.025 as the CoC for 35mm film, which suggests a CoC of .02-.015 for the 10D. This CoC number is derived from the desired final print size and viewing distance (typically 8x10 at 10", or something like that).
-harry

[brault]

I believe the hyperfocal distance depends on the size of the circle of confusion as well as the focal length of the lens.

If you enlarge two identical (camera subject distance, f-stop, etc) pictures from the same focal length lens (one taken with a 35 mm SLR and one taken with a DSLR) to 10X12 the apparent depth of field will be different.

There are two DOF calculators at the following link which allow you to input the 1.6 multiple, f-stop and focal length and get the hyperfocal distance.

http://www.outsight.com/hyperfocal.html

Frank B

[petiot]

Hi

Everyone thank you for your answers (very usefull). I didnt know about the "intelligent" evaluative mode of the 10D, but as cleaver as it is, i dont always like hte resuslt. I got around by using center weighted

Thank you also for the CoC suggestion and the link. i will update my table :)

Thank you

Dan