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One thing i dont get about overrides

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Offline Miguel-Sx500IS

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  • Canon Powershot Sx500 IS - CHDK 1.00D
One thing i dont get about overrides
« on: 07 / January / 2014, 10:14:30 »
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Hi!

I started using Chdk just a month ago..

There is one thing i dont understand.

I have a Sx500 is camera, the original aperture values are 3.4 and 8.0

I was only using chdk for shooting in raw and some other features, but i was affraid of using the overrides, because i fear they may damage my camera.

But curiosity won, and i tryed using the Av override,

the available value options i get in the chdk menu are from 3.4 to 16.0, so, i dont get a wider aperture, but yes a smaller one. Never the less, if a shoot in AV 16 override, the canon display shows f/11, not f/16.

The thing i dont get is the next one:

I was not expecting the canon display to show the override aperture, (i guess it happens with Tv too, doesnt it? i mean, its shown on the original camera display?), i thought the canon display would remain in 8.0, and that only the CHDK osd would show me f/16.

it is even shown on the playback mode when i double click display, and i guess it will be that way on the PC softwares and exiff files..

If the canon display shows the f/11, i should consider that the camera is really doing an f/11 aperture, and not an f/8.

The thing is, if the camera can do an f/11 aperture, to the point that it shows it on the original display, why didnt canon released it that way? can it be because it damages the camera, not meant to do that, or because the other features are not design for that aperture either?

i havent taken many photos with f/11 yet, do you think the depth of field difference can be apreciated?

the subject distance override activates when you activate av override for that purpose? doesnt it?

and, how does that work? how can chdk make the camera focus farther?



well, sorry for the long posts, and sorry for my english, i hope someone can take away this doubts..



 
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Offline reyalp

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Re: One thing i dont get about overrides
« Reply #1 on: 07 / January / 2014, 21:31:35 »
Quote from: Miguel-Sx500IS on 07 / January / 2014, 10:14:30
the available value options i get in the chdk menu are from 3.4 to 16.0, so, i dont get a wider aperture, but yes a smaller one. Never the less, if a shoot in AV 16 override, the canon display shows f/11, not f/16.
This isn't surprising, just because CHDK asks for F/16, doesn't mean your camera can actually do it. The actual F number will also depend on zoom.

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I was not expecting the canon display to show the override aperture, (i guess it happens with Tv too, doesnt it? i mean, its shown on the original camera display?),
As you see, the Canon display can show some values outside the normal range. They may or may not be correct.

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If the canon display shows the f/11, i should consider that the camera is really doing an f/11 aperture, and not an f/8.
Maybe, maybe not. The best to to find out if it is working is to test by comparing photos. To compare you can take 3 photos, using manual controls
1) correctly exposed, F/8 set in the canon firmware, with no overrides.
2) shutter 1 stop shorter (if #1 was 1/60th, got to 1/120th), AV F/8 in canon firmware, no overrides
3) same shutter as #1, override AV to F/11

ISO should be the same for all, and they should all be of the exact same scene.

#2 and #3 should be identical exposure, and both should be darker than #1.

If #3 looks like #1, then the override isn't working.
If #3 is lighter than #2, then it isn't going all the way to F/8. If it's darker, then it's more then F/8

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The thing is, if the camera can do an f/11 aperture, to the point that it shows it on the original display, why didnt canon released it that way? can it be because it damages the camera, not meant to do that, or because the other features are not design for that aperture either?
Hard to know, but probably the quality suffers due to the very small aperture. It's very small so it starts to act like a pinhole camera.

Damage to the camera seems unlikely to me, but we can't be absolutely certain.

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i havent taken many photos with f/11 yet, do you think the depth of field difference can be apreciated?
Again, the best way to know is to take two photos of the same scene and compare them.

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the subject distance override activates when you activate av override for that purpose? doesnt it?
SD override should not be connected to AV override, I'm not sure I understand the question.
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and, how does that work? how can chdk make the camera focus farther?
SD override just lets you control the focus distance. If your camera has manual focus, then there isn't much reason to use it.
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