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Showing shooting data

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Offline sf_photo

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Showing shooting data
« on: 15 / February / 2009, 21:49:00 »
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Is there a way in review mode to view the shutter speed and (indicated) f-stop used via CHDK as Canon does not seem to provide this with my SD800?

thanks
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Offline fe50

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Re: Showing shooting data
« Reply #1 on: 16 / February / 2009, 06:17:06 »
Quote from: sf_photo on 15 / February / 2009, 21:49:00
Is there a way in review mode to view the shutter speed and (indicated) f-stop used via CHDK as Canon does not seem to provide this with my SD800?

No, the shown data there is from the EXIF of the JPEG image which contains only the Canon meta data - CHDK can't write the meta data to the JPEGS yet.
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Offline fudgey

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Re: Showing shooting data
« Reply #2 on: 16 / February / 2009, 13:43:56 »
Canon MakerNotes section in the JPEG EXIF tag contains the overrided values, but the camera does not show those in review mode as you have noticed.

This probably would be possible to read those from the jpegs in review mode and put them in CHDK OSD, but I believe that would be a lot of trouble for little gain. If exif tag needs to be searched somehow (instead of just going to a byte offset found in a header), it will probably be fairly slow to update too.
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Offline sf_photo

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Re: Showing shooting data
« Reply #3 on: 22 / February / 2009, 14:01:06 »
Thanks for the comments,

Via CHDK I turned on the OSD>misc. values, to show aperature but there is no option for showing shutter and Canon only shows when speeds are lower than 1/30 sec.

Hence my interest in viewing the settings used in review mode.


Does anyone know the highest 'built in' shutter speed of the SD800? I made a photo in bright sun and the camera chose 1/640 at f7.1 - I then (via CHDK) set the ND filter out and made another photo - the shot was overexposed and the EXIF data shows the same settings. I was trying to force a higher shutter speed.


Thanks!


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Offline fudgey

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Re: Showing shooting data
« Reply #4 on: 22 / February / 2009, 14:26:58 »
You can probably find the maximum from Canon's website, it will likely be something like 1/1250 s. Why do you want to show aperture when you camera doesn't have an iris and only zoom affects aperture? To see when the ND filter is active?

Canon's autoexposure will not know that CHDK has been set to disregard Canon's autoselection of ND, that's why your camera overexposed.

To fix exposure, you must either also override Tv, or set a strong enough exposure compensation (via propcases -4 stops should be possible even thought normal limit is -2) to fix it.
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Offline fe50

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Re: Showing shooting data
« Reply #5 on: 22 / February / 2009, 14:32:03 »
Quote from: sf_photo on 22 / February / 2009, 14:01:06
Does anyone know the highest 'built in' shutter speed of the SD800?

The range is 15 seconds to 1/1,600 sec for the SD800 (Canon SD800 data sheet)
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Offline sf_photo

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Re: Showing shooting data
« Reply #6 on: 22 / February / 2009, 14:49:58 »
I was away looking up the speed when you all posted - thanks.

As to showing the f-stop, yes I guess that would show if the ND filter was in use but I wonder if this 'speed' is not a 'real' speed and the ND filter is expected to make this an effective speed?

I will have to research how to 'override Tv' as suggested. Found this page:
http://chdk.wikia.com/wiki/CHDK_firmware_usage/AllBest#Override_shutter_speed_value

but am not clear on the concept - it states "Choose a new shutter speed which overrides the camera's shutter speed in all modes"


thanks!
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Offline fe50

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Re: Showing shooting data
« Reply #7 on: 22 / February / 2009, 15:21:42 »
@sf_photo

The f-stop changes with the ND filter - from min (ND filter off) to max (ND filter active), e.g. on the Ixus 870 from F/2.8 (ND off) to F/8.0 (ND on).
The "aperture" also changes (mechanically) with the zoom, e.g. from F/2.8 to F/5.8 (ND off) and F/8.0 to F/16 (ND on).

If you set up an Tv override in CHDK - let's say 1/1.6000s - this Tv will be used independend from whatever the Canon firmware automatic would set up and show on it's OSD...
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Offline sf_photo

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Re: Showing shooting data
« Reply #8 on: 26 / February / 2009, 22:07:31 »
Sorry to need so much 'hand holding'.

I set the
Override shutter speed to 10
and the
Value factor to 1

But it is not using 1/10000 in fact it still uses whatever it wants.

Still not sure why when I set the ND filter out (this was before setting any over ride) that the camera still used the same 1/640 shutter and F-stop as when the ND filter option was turned off.

I can upload images to show this if it would help or the EXIF data.


Thanks!
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Offline fe50

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Re: Showing shooting data
« Reply #9 on: 27 / February / 2009, 04:20:43 »
Quote from: sf_photo on 26 / February / 2009, 22:07:31
I set the
Override shutter speed to 10
and the
Value factor to 1
But it is not using 1/10000 in fact it still uses whatever it wants.

10 x 1 = 1/1000 ??? ?
If you want 10 seconds - that's it; if you want 1/10000 then set Override=1/10000 and Value factor 1

Quote
Still not sure why when I set the ND filter out (this was before setting any over ride) that the camera still used the same 1/640 shutter and F-stop as when the ND filter option was turned off.

Quote from: fe50 on 23 / February / 2009, 03:22:38
...
the Canon firmware swings in the ND filter in brigth light conditions, e.g. in direct sunlight (that's the equivalence to the highest F-stop number, e.g. F/8.0). Then it calculates the exposure time with this self-choosen ND filter state - if you set the ND filter to OUT, the original Canon firmware don't know this, the calculated exposure setting is wrong & your shots will be overexposed.
...
  ;)
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