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Shoot in 3:2 DSLR format?

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Offline gse53

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Shoot in 3:2 DSLR format?
« on: 04 / December / 2008, 12:57:57 »
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This may have been covered before but I could not find it in my search. I would like to see a choice of shooting in a DSLR aspect ratio of 3:2 for printing 4x6 photos without cropping, similar to the "widescreen" choice on my A590is. I had it on my old Olympus P&S and it come in handy for just taking family snapshots. Thanks for the work you did on the firmware. Terrific job!!

Gary
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Offline PhyrePhoX

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Re: Shoot in 3:2 DSLR format?
« Reply #1 on: 04 / December / 2008, 13:07:02 »
well you could load a 3:2 grid file, Grids - CHDK Wiki
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Offline gse53

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Re: Shoot in 3:2 DSLR format?
« Reply #2 on: 04 / December / 2008, 13:15:50 »
But it still captures the picture in 4:3 (3264 x 2448). The grid only shows what to compose for 3:2. I would like the actual picture to be in 3:2 (3264 x 2176). Widescreen is 3264 x 1832 or in 16:9. Basically want an in camera crop like the widescreen.

G
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Offline fudgey

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Re: Shoot in 3:2 DSLR format?
« Reply #3 on: 04 / December / 2008, 14:26:42 »
I guess for RAW this would be very easy.

To find out if you really actually want this for JPEGs, you should try if the in-camera browser is even able to show such images. Crop a jpeg yourself on a PC and put it back to the camera and test it...

And if it works, we probably don't know how to resize it while it's being written, so it would probably be post-save cropping operation which takes a while, requires a port of something like jpegtran to CHDK and is better done outside the camera really, since it can be done just as losslessly there as in the camera, but faster and without increasing CHDK binary size or requiring any trouble from devs.
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Offline gse53

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Re: Shoot in 3:2 DSLR format?
« Reply #4 on: 04 / December / 2008, 15:01:41 »
I did not try what you said as I do not have my card reader with me. But, I took a picture in widescreen mode and it does what you describe. It saves a cropped file. The OSD also displays a cropped view with black bars top & bottom. The playback displays the cropped file. My guess is if you can see how Canon did this with widescreen, 3:2 should be easy to do. If this method is not visible in the firmware, then it would be too difficult. Thanks for trying

G
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Offline dzsemx

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Re: Shoot in 3:2 DSLR format?
« Reply #5 on: 04 / December / 2008, 15:24:55 »
yes, there is widescreen mode in original firmware on many cameras, only available at one resolution
so maybe there are some functions which sets up the image parameters
i would like to see some custom resolutions too
btw, mostly images taken with other canon cameras can be viewed easily on ours too, for ex A650IS (4000*3000) images can be wieved on A630, which i didn't expect, because we know that the in-camera JPEG decoding is quite simple, inflexible.
but when the image is resized on computer, the file structure changes a little bit, so it will be not recognized by the camera
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Offline fudgey

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Re: Shoot in 3:2 DSLR format?
« Reply #6 on: 04 / December / 2008, 15:57:49 »
Well, looks like my a570is doesn't have a problem with 3:2 cropped images, at least if its done with care:

input img_7674 from a570is full resolution is 3072x2304.
3:2 aspect 3072/1.5=2048 => target resolution 3072x2048, need to discard (2304-2048)/2 = 128 pixels from both top and bottom:

jpegtran -perfect -crop 3072x2048+0+128 -copy all <img_7674.jpg >IMG_0001.JPG

Tags of IMG_0001.JPG are now partially incorrect about the resolution but image was losslessly cropped to 3:2 as desired. Incorrect tags found by exiftool are:

MakerNotes:CanonImageHeight: 2304
EXIF:RelatedImageHeight: 2304

exiftool -EXIF:RelatedImageHeight=2048 -o IMG_0002.JPG IMG_0001.JPG

Sadly MakerNotes:CanonImageHeight is not writeable by exiftool. We could find out how it decodes it and edit it that tag, but apparently it's not necessarily because all three images (original, cropped, cropped with one fixed tag) appear to display fine on my camera. It also reports the correct resolution on screen.

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Offline gse53

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Re: Shoot in 3:2 DSLR format?
« Reply #7 on: 04 / December / 2008, 16:49:13 »
One resolution would be fine, just as the widescreen and also the datestamp function, which saves at 1600x1200. A file ready to print a 4x6 out of the camera would be perfect. 1800 x 1200 would print a 4x6 at 300 dpi. You do not need anymore info than that. My GF borrows my camera and she complains when the lab cuts off peoples heads with the cropping. She sends the files right out of the camera to the lab and does not (and will not) understand about resolution and aspect ratio. I do not know why Canon does not do this for that very reason. As I stated before, my old Olympus had a 3:2 option.

Thanks,

G
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Offline fudgey

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Re: Shoot in 3:2 DSLR format?
« Reply #8 on: 04 / December / 2008, 17:54:37 »
You really could just set the camera use a suitable grid to anticipate the cropping. The images will still be the same size but she won't be shooting partial heads any longer if they're hidden on the LCD.

Anything else will probably not happen soon, if ever because we have no clue how to do it the neat & efficient way and I'm probably not the only one who doesn't want to have it done the slow in-camera post-processing way that nobody's going to use because it sucks so much...

As for the grids, see http://chdk.wikia.com/wiki/Grids. I've never tried creating my own (the camera's internal grid has so far been enough for my uses), but you can find examples there, even readily written ones for 3:2 it seems. And if a grid line showing the border isn't enough (I would think your GF can learn to keep people's heads inside the lines though), you can (if I'm not mistaken) write a more aggressive grid that masks the top&bottom entirely.
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Offline PhyrePhoX

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Re: Shoot in 3:2 DSLR format?
« Reply #9 on: 05 / December / 2008, 01:14:44 »
see reply #2 ;)
i really think this will be the best and simpliest solution.
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