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Old Dec 28, 2006, 6:59 AM   #1
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Hi,

I've been experimenting with my 350D (Canon 18-55 Kit, Sigma 70-300 DG APO & Canon 10-22) and have been looking for an EASY and PRECISEway to set the focus to the correct value for the hyperfocal distance.

Problem is that the displays on the lensesare far away from being precise and I've got the feeling Iget the right setting only by chance

Is there any other way (firmware?) to electronically set the focus to the hyperfocal distance? In my opinion, calculating the value and setting the lense automaticallyshould bean easy task for a microprocessor based camera. But I couldn't find anything in the manual. Has Canon ignored this important function?

Thanks for your help,

fisheye
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Old Jan 1, 2007, 3:51 PM   #2
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Hi,

I just got one of those with the 18-55 lens and was looking for any/all info on it when I came across this forum. I saw your post and thought, I should know this... I had to look it up in my NYIP lessons.

my understanding about hyperfocal is that you use the smallest aperture possible (highest f/stop number) and that will give you your best hyperfocal distance setting. it looks easier with the lens that have "depth of field" markings. This would have the infinity symbol on one side/end.

I'm assuming that if I'm correct with what I said above, then it would be a simple matter of using the Av setting on the camera, set the f/stop as small (high)as possible and shoot away.

after rereading your post, i'm not sure I've answered your question. I'm not sure what you mean by "correct value". could you explain please?

Fisheye wrote:
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Hi,

I've been experimenting with my 350D (Canon 18-55 Kit, Sigma 70-300 DG APO & Canon 10-22) and have been looking for an EASY and PRECISEway to set the focus to the correct value for the hyperfocal distance.

Problem is that the displays on the lensesare far away from being precise and I've got the feeling Iget the right setting only by chance

Is there any other way (firmware?) to electronically set the focus to the hyperfocal distance? In my opinion, calculating the value and setting the lense automaticallyshould bean easy task for a microprocessor based camera. But I couldn't find anything in the manual. Has Canon ignored this important function?

Thanks for your help,

fisheye
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Old Jan 2, 2007, 1:41 AM   #3
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Hi,

as far as I know, it's not all about setting the aperture to minimum size. Hyperfocal distance means that for each aperture value there is a focus distance which makes sure that everything after that distance is sharp. For example, it should be possible to combine Av and focus in a way that everything beyond 1.3m or 21m or 0.7m is sharp. It would be your choice and the advantage is that you don't have to setaperture to the minimum size.

[...] the hyperfocal distance setting ... is simply a fancy term that means the distance setting at any aperture that produces the greatest depth of field.

How to Use Your Camera, New York Institute of Photography, 2000.

Also see here: http://www.dofmaster.com/hyperfocal.html

It can be calculated but one has to know the size of the sensor (which is of course a constant value if you use the same gear). Beside this, it's a little bit complicated to calculate so using a simple calculator takes a minute or so which is the reason why there exist tables where you can look up this number.

But, even if you've got this number for the distance, applying it to your camera is a tricky task as you've to do it MANUALLY on your lens and this is the reason for my posting. The focus distance's display or scale on the lens is by far not precise enough to correctly set it. Try to set the focus to 12.7m, see what I mean?

regards,

fisheye
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Old Jan 2, 2007, 2:38 PM   #4
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This is is basically what the A-Dep mode does, so long as you can cover your far and near points of focus with the AF sensors.

In practice, I would switch the lens to manual after operating in A-Dep mode, having taken note of the f stop chosen. Then close down the lens another couple of stops to ensure the far point is sharp enough, as it tends to err on the near focus side.


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Old Jan 2, 2007, 7:26 PM   #5
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luceberg,

yes, that's a good idea although I don't find the A-Dep mode very practical. It consumes a lot of time to set it and it's only suitable for non-moving objects.

But using the A-Dep mode and then setting the lens to manual mode could work pretty closely to what I had in mind. :-)

Nevertheless, I would be nice if Canon would include a non auto focus based mode for setting the hyperfocal distance.

Thanks for the hint!

fisheye


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Old Jan 2, 2007, 7:35 PM   #6
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Just found a nice article describing your solution more detailed. They also suggest to turn off the auto focus after having "calibrated" the lens to the hyperfocal distance.

http://www.luminous-landscape.com/tutorials/dep.shtml

What I would like Canon to do is to include a hyperfocal distance mode where either the apropriate aperture value corresponding to a manually set focus distance is set or the focus is set to a distance corresponding to a manually set aperture value.

Then of couse we have the challenge of the apropriate shutter speed and ISO setting...

Things were easier back in the old days when the scales on the lens had everything displayed properly... (I start to sound like my fathter)

:-)

thanks,

fisheye
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Old Jan 2, 2007, 8:30 PM   #7
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Fisheye wrote:
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What I would like Canon to do is to include a hyperfocal distance mode where either the apropriate aperture value corresponding to a manually set focus distance is set or the focus is set to a distance corresponding to a manually set aperture value.
It depends on the lens...

-> Most low-end zooms (including Canon's) are varifocal in design meaning their focal distance changes as you zoom in or out so a fix marking for the aperture just would not work as a DOF indicator - In the old push-pull day various curves of different colored apertures is traced along the lens barrel, but with the popularity of two-touch such color curves are no longer possible.

See this picture below - The Sigma EX, a parafocal design (where the focal distance is fixed when zoomed), on the left has clearly marked DOF scale for hyperfocal/DOF whereas the 28-135 IS (a varifocal instead) on the right does not:




The red marking on the 28-135 IS are for the various focal lenght distance scale which are actually changing as the zoom is varied when used in the IR mode (an another indication of varifocal)!
-> You would need many varying aperture scales for each focal lenght with a varifocal lens :shock:
... and why the distance scale is imprecise in your zoom
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