Shot Histogram Request - page 39 - CHDK Releases - CHDK Forum

Shot Histogram Request

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Re: Shot Histogram Request
« Reply #380 on: 29 / August / 2013, 10:14:52 »
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Thanks, especially for the nice explanations. That helps a lot!
I will do some testing and report how it goes.

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Re: Shot Histogram Request
« Reply #381 on: 29 / August / 2013, 17:40:09 »
Thanks, especially for the nice explanations. That helps a lot!
I will do some testing and report how it goes.
Thanks for your interest, and I hope you get it to work for you.

By the way, if you press the <display> key while the script is running, it toggles the ND filter in or out. It changes the exposure for the next shot, but then the script corrects for it. However, I haven't adjusted for the Bv96 change yet, so the script thinks it's suddenly darker out, and lowers the exposure. It's a work in progress, but it's interesting to try out.

I did a short time lapse on Spencer's Butte last night. Clouds blocked the sun, but the time lapse was still interesting. I tested out my new wide angle lens attachment for the G1X, and did some panning and zooming with my video edit program to make it more interesting.

http://www.youtube.com/watch?v=wcI_jIY69yI#
« Last Edit: 02 / September / 2013, 16:57:53 by lapser »
EOS-M3_120f / SX50_100b / SX260_101a / G1X_100g / D20_100b
https://www.youtube.com/user/DrLapser/videos

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Re: Shot Histogram Request
« Reply #382 on: 30 / August / 2013, 04:09:44 »
The sun was streaming through small holes in moving dark clouds in this sunset time lapse video. The meter I had on the sky averaged everything out and ended up blowing out the small bright spots. This would be a good time to use a histogram based exposure compensation function, which I plan to add soon.

http://www.youtube.com/watch?v=kc2CeWEkRuc#
EOS-M3_120f / SX50_100b / SX260_101a / G1X_100g / D20_100b
https://www.youtube.com/user/DrLapser/videos

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Re: Shot Histogram Request - ND Filter Tests
« Reply #383 on: 30 / August / 2013, 16:43:50 »
In general, the aperture propcases do not control the ND filter (there may be some exceptions). You should use set_nd_filter for that.

Since d20 has CAM_HAS_IRIS_DIAPHRAGM is undefined, the set_av* functions should be NOOP.

Some further discussion of ND control http://chdk.setepontos.com/index.php?topic=10432.0
Thanks for that info. Do you know an easy way to read the status of the ND filter when the script starts?

My script toggles the ND filter state when you press <display> during a time lapse. I don't include the ND filter in my Bv calculation because I need the density. But I just realized that I can set my smoothing parameters to 0 and accurately measure the density with my current script.

The ND density I get with the SX260 is 312 EV96, or 3.25 f-stops. That's using my post shot meters from the raw buffers while taking pictures of my favorite blank wall. Has anyone else measured it using the camera meter? I think you could take two pictures (or two half-shoots) in Av mode with fixed ISO and compare the get_tv96() values with ND in and ND out.

I'll try measuring ND density with the rest of my cameras. I'm hoping it will be 3.25 for all of them.
EOS-M3_120f / SX50_100b / SX260_101a / G1X_100g / D20_100b
https://www.youtube.com/user/DrLapser/videos


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Online reyalp

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Re: Shot Histogram Request - ND Filter Tests
« Reply #384 on: 30 / August / 2013, 16:53:24 »
Thanks for that info. Do you know an easy way to read the status of the ND filter when the script starts?
edit: fixed quote.
I don't know about easy, but that's the subject discussed in the thread I linked.

Quote
The ND density I get with the SX260 is 312 EV96, or 3.25 f-stops. That's using my post shot meters from the raw buffers while taking pictures of my favorite blank wall. Has anyone else measured it using the camera meter? I think you could take two pictures (or two half-shoots) in Av mode with fixed ISO and compare the get_tv96() values with ND in and ND out.
For cameras without an iris, these are normally determined from propcase values and entered in platform/<camera>shooting.c aperture_sizes_table. See http://trac.assembla.com/chdk/browser/trunk/platform/d10/shooting.c for example.

I'm not sure how it is with cameras that have both, the values aren't recorded in aperture_sizes_table, but I would expect there is still a propcase somewhere that reflects the nd+aperture value.
« Last Edit: 01 / September / 2013, 14:16:36 by reyalp »
Don't forget what the H stands for.

Re: Shot Histogram Request
« Reply #385 on: 01 / September / 2013, 13:10:07 »
I still have the flickering issue. I uploaded a time lapse to show the problem... The log file is also attached.

Marsai Mara Time Laps - CHDK time lapse flickering issue

Is there a way to see if the ND filter was in or out from the EXIF data of a photo?

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Online reyalp

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Re: Shot Histogram Request
« Reply #386 on: 01 / September / 2013, 14:19:45 »
Is there a way to see if the ND filter was in or out from the EXIF data of a photo?
I'm not sure how this works on cameras that have both an ND and an adjustable filter, but I would expected it to be recorded somehow if the Canon firmware selected. Some digging with exiftool would probably clarify things. I'd take test shots where you know the ND is in or out and then compare the output.
Don't forget what the H stands for.

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Re: Shot Histogram Request
« Reply #387 on: 01 / September / 2013, 14:39:00 »
I still have the flickering issue. I uploaded a time lapse to show the problem... The log file is also attached.
Is there a way to see if the ND filter was in or out from the EXIF data of a photo?
It looks like everything worked great until you got to IMG_1704. This image was 2 f-stops brighter than IMG_1703. Will you look at those 2 pictures and confirm that the second one is a lot brighter than the first?

As the cows walked in front of the sun, the meter reading changed by 1 f-stop. The script handled that ok, and you'll notice that the ground in front of the cows briefly gets brighter while the cows block the sun.

However, the sudden 2 f-stop change is what messed things up. Specifically, the bvdelta parameter is designed to gradually underexpose the images as it gets darker. But it doesn't take into account the ND filter. So if the ND filter suddenly went in, the script would think it got suddenly darker.

Anyway, the flickering would be explained if you pressed the <display> key right before IMG_1704, and the ND filter is about 2 f-stops. Did you press display?

I'm not sure if the ND filter state is in the EXIF. I don't think so, at least when it's set from a script or CHDK menu. But from the shutter speed while the sun was in the frame, it looks like the ND filter was IN when you started. Maybe you pressed <display> after it got dark? That won't quite work yet, but I'll add ND filter control soon.

Thanks for doing the video. Other than the end, it's a great time lapse!
EOS-M3_120f / SX50_100b / SX260_101a / G1X_100g / D20_100b
https://www.youtube.com/user/DrLapser/videos


Re: Shot Histogram Request
« Reply #388 on: 01 / September / 2013, 15:06:28 »
I'm not sure if the ND filter state is in the EXIF. I don't think so, at least when it's set from a script or CHDK menu.
I've tested it and can confirm that the EXIF will indicate if Canon firmware used (or wanted to use) the ND filter.  CHDK override of ND filter does not get recorded in the EXIF.
Ported :   A1200    SD940   G10    Powershot N    G16

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Re: Shot Histogram Request
« Reply #389 on: 01 / September / 2013, 16:39:48 »
I've tested it and can confirm that the EXIF will indicate if Canon firmware used (or wanted to use) the ND filter.  CHDK override of ND filter does not get recorded in the EXIF.
Thanks, that's nice to know.

I wonder if there's a propcase that indicates the ND filter state for writing to the Exif, similar to the extra tv96 propcase. In other words, is there a way that we could get the nd filter state to appear in the EXIF when set by CHDK?
EOS-M3_120f / SX50_100b / SX260_101a / G1X_100g / D20_100b
https://www.youtube.com/user/DrLapser/videos

 

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