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Shot Histogram Request

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Re: Shot Histogram Request
« Reply #390 on: 02 / September / 2013, 15:49:41 »
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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?

I attached the two pictures. I would say they are about the same brightness. Things mess up with IMG_1706, which is darker (and the ISO drops from 400 to 320 for this picture only) and IMG_1707 is way brighter.

I just noticed that the EXIF data of the pictures and the log file data is always shifted by one picture. So in reality IMG_1706 is the one where the ISO drops to 320 for only one picture, but the log file tells its IMG_1705.
To get back to your question about IMG_1703 and IMG_1704... if that is also shifted by one picture, it doesn't make a difference, because IMG_1705 is about the same brightness as the two previous pictures.

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 was not quite sure, so I did an other test today and made sure not to touch anything this time and I had the same issue of flickering. As soon as it gets dark the exposure jumps around like crazy.

By the way, should the display go completely dark when pressing the <SET> button? It doesn't seem to make a change when I press it. The image is flashes up every time the camera takes a picture.
I can toggle the information string by pressing the <UP> button and the <RIGHT> button toggles the displaying of the meters. But the <LEFT> and the <DOWN> button don't seem to make a change.

I'm still experimenting with the build and script you attached for me...

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Re: Shot Histogram Request
« Reply #391 on: 02 / September / 2013, 19:44:37 »
I attached the two pictures. I would say they are about the same brightness. Things mess up with IMG_1706, which is darker (and the ISO drops from 400 to 320 for this picture only) and IMG_1707 is way brighter.
Thanks a lot for all the testing. I noticed that the trouble started right after the shutter time reached 1 second. That's 0 tv96 units. Over 1 second is negative tv96, and under is positive. So the problem shows up when going from positive to negative tv96 and vice versa. Here's the relevant part of your log file:
Code: [Select]
1700 650 60 401 -33 -1 7595 1/1.022 10   
1701 710 50 401 -34 -2 7614 1/1.007 10   
1702 660 60 401 -33 -1 7585 1.000 10   
1703 650 60 401 -34 -2 7585 1.015 10     first picture over 1 second shutter time (tv96<0)
1704 680 50 401 165  0 7595 1.015 10    glitch detector prevented exposure change
1705 680 60 313 164 132 7585 1/2.00 10    glitch detector off for next 5 shots
1706 710 50 401 -239 -207 7605 1.744 10    tv96 going from positive to negative
1707 1090 50 401 185 153 7585 1/1.731 10   
1708 -20 50 401 -195 -163 7585 1.874 10   
The log prints the calculated exposure change measured from the current shot, which is then applied to the next shot after smoothing and glitch detection. The problem is that the picture taken with 1.015 second shutter time was much brighter than the picture taken with 1.000 shutter time. My get_shot_meter() function could be measuring wrong, but I don't have the measurements in the log data. I'll attach a new script and build which might help me figure out what happened, if you can get it to happen again.

I also noticed you're using exposure compensation. It looks like the exposure may be off by about that amount. Try running the test with it set to 0 and see if that makes a difference.

I would like to see the logs from any other times it happened to see if they also show it starting at 1 second shutter time.

I doesn't look like the ND filter had anything to do with it. The "display" key is what controls the ND filter while the script is taking pictures, not the <left> key as I said previously. I corrected it in the post.

The <set> key turns the screen off and on. I just finished a new version that keeps it off without flashing. Also, the <left> key should now toggle the CHDK OSD and console displays, so all you see is the picture. Up toggles the data line on top, and right toggles the meter area display. The active meter is green. If you want it to be red, press <set> while you're setting up the meters, then <menu> to start taking pictures.
EOS-M3_120f / SX50_100b / SX260_101a / G1X_100g / D20_100b
https://www.youtube.com/user/DrLapser/videos

Re: Shot Histogram Request
« Reply #392 on: 03 / September / 2013, 11:07:35 »
I also noticed you're using exposure compensation. It looks like the exposure may be off by about that amount. Try running the test with it set to 0 and see if that makes a difference.
Okay, I'm currently capturing a new time lapse. By the way, what settings do you use on the camera? Which mode do you choose? Maybe I'm just setting it up wrongly. I'm currently using Av mode, because I can choose the aperture and that is probably one of the only things that the script doesn't override.

I would like to see the logs from any other times it happened to see if they also show it starting at 1 second shutter time.
Here you go... It is just as you expected, it messes up after it reaches a shutter time of 1 sec.
Code: [Select]
3605 -280 50 600 -34 -2 7174 1/1.106 10   
3606 -310 50 600 -32  0 7184 1/1.106 10   
3607 -340 60 600 -35 -3 7184 1/1.083 10   
3608 -310 60 600 -33 -1 7194 1/1.075 10   
3609 -360 60 600 -35 -3 7174 1/1.052 10   
3610 -340 50 600 -33 -1 7184 1/1.044 10   
3611 -380 60 600 -35 -3 7184 1/1.022 10   
3612 -390 60 600 -33 -1 7184 1/1.015 10   
3613 -410 60 600 -32  0 7184 1/1.015 10   
3614 -440 60 600 -34 -2 7184 1.000 360   
3615 -420 60 600 -36 -4 7184 1.029 10   
3616 -440 60 600 146  0 7184 1.029 10   
3617 -430 50 542 146 114 7194 1/2.00 10   
3618 -370 50 600 -233 -201 7174 1.929 0     
3619 40 60 600 170 138 7194 1/1.404 10   
3620 -1290 50 600 -174 -142 7184 1.986 10   
3621 -180 60 600 171 139 7174 1/1.374 10   
3622 -1330 60 600 -176  0 7174 1/1.374 10   
3623 -110 50 600 -177 -145 7184 2.07 10   
3624 -170 50 600 172 140 7174 1/1.325 10   
3625 -1420 50 600 -181 -149 7174 2.21 80   
3626 -190 50 600 174 142 7174 1/1.260 10   
3627 -1590 60 600 -176 -144 7174 2.24 10   
3628 -240 50 600 174  0 7174 2.24 10   
3629 -1690 50 600 174 142 7194 1/1.242 80   
3630 -1620 50 600 -188 -156 7174 2.48 10   
3631 -260 60 600 177 145 7174 1/1.147 10   
3632 -1880 50 600 -182 -150 7174 2.57 10
The <set> key turns the screen off and on. I just finished a new version that keeps it off without flashing. Also, the <left> key should now toggle the CHDK OSD and console displays, so all you see is the picture. Up toggles the data line on top, and right toggles the meter area display. The active meter is green. If you want it to be red, press <set> while you're setting up the meters, then <menu> to start taking pictures.
Thanks. I found out why my display didn't blank completely... I still had a 2 sec review in the original canon menu settings. It seems like chdk doesn't override that :)

Re: Shot Histogram Request
« Reply #393 on: 03 / September / 2013, 12:12:45 »
Okay, I'm currently capturing a new time lapse.

The result is still the same... Attached is the log file. I saw that you added some information to the log.


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Re: Shot Histogram Request
« Reply #394 on: 03 / September / 2013, 14:49:11 »
The result is still the same... Attached is the log file. I saw that you added some information to the log.
Thanks, that's very helpful. According to the log:

IMG_6282 has tv96=0 (1.000 sec) and the meter reading is normal
IMG_6283 has tv96=4 (1.029 sec) and the meter reading says it much brighter than IMG_6282

Will you check those two pictures for me and see if that's the case? If not, what was the first image that was suddenly much brighter.

6282 -360 60 400 -36 -4 7409 1.029 10   
_2 -327 -184 -294 -539 | -275 148 0 603
6283 -340 50 400 102  0 7409 1.029 10   
_2 -27 -14 -25 -33 | -109 116 -4 603

I checked the logs for my G1X, and I've had several times where I passed through 1 second shutter time without a problem. I also can't find an error in the script. So I'm thinking it may be a camera setting that you're using that I'm not. The camera does do different things starting at 1 second, including dark frames. I always set dark frames OFF in the CHDK menu.

Go through all the <set> menu Canon settings and make sure everything is OFF. Set the White Balance to cloudy. Make sure DR Correction and Shadow correct are OFF. Then go through the Canon record menu and set all that to off, including IS and whatever else you can set to off. Basically, you don't want the camera doing anything automatically. All the CHDK overrides should be OFF too. Just go through every menu you can get to and try to turn everything off. Also, it looks like your clock isn't set right, so it would help to set it to the correct date and time, unless it's actually October on your planet :)

Incidentally, you can set the max ISO for the G1X to 1600 and still get really good pictures. If you do that, the shutter time will stay under 1 second, and it won't trigger the bug (unless you keep going until it gets REALLY dark. But for testing, it would be nice to stick with 400 max, if you find a camera setting that may be the cause.

Good luck.
EOS-M3_120f / SX50_100b / SX260_101a / G1X_100g / D20_100b
https://www.youtube.com/user/DrLapser/videos

Re: Shot Histogram Request
« Reply #395 on: 03 / September / 2013, 16:17:46 »
IMG_6282 has tv96=0 (1.000 sec) and the meter reading is normal
IMG_6283 has tv96=4 (1.029 sec) and the meter reading says it much brighter than IMG_6282

Will you check those two pictures for me and see if that's the case? If not, what was the first image that was suddenly much brighter.

That is not the case IMG_6282 and IMG_6283 are about the same brightness. IMG_6283 even is slightly darker. The first image that is much brighter is IMG_6286.

Okay I will try to play around with the camera settings... when it is dark enough it starts flickering right away when I start the script, so it is quite well reproduce able the problem.

It seems to be quite systematic the brightness changes. I took a couple of photos when it was quite dark outside. And when I looked at the photos, I realized that it is always the same number of pics between the brightest pictures. So I stiched together only the brightest photos to see if they match... The result is attached.

Thanks for your great support. I will be away for a couple of days, but I will report if I found something new.

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Re: Shot Histogram Request
« Reply #396 on: 04 / September / 2013, 18:33:51 »
IMG_6282 has tv96=0 (1.000 sec) and the meter reading is normal
IMG_6283 has tv96=4 (1.029 sec) and the meter reading says it much brighter than IMG_6282
Will you check those two pictures for me and see if that's the case? If not, what was the first image that was suddenly much brighter.
That is not the case IMG_6282 and IMG_6283 are about the same brightness. IMG_6283 even is slightly darker. The first image that is much brighter is IMG_6286.
Hmm, well the meter readings seem reasonable, just 2 EV brighter for all the meters. I'm reading the raw buffer, so if it got suddenly brighter but the jpg looked the same, it sounds like the camera is doing something automatically for negative tv96 (shutter time >1 second), then compensating for it when it makes the jpg.

I know Canon did some tricks to get lower noise at high ISO for the G1X. Maybe this is one of them. I recall a menu setting for Noise reduction at high ISO. I set it to "normal". See what you have it set to.

When I get some time, I'll try experimenting by taking pictures at tv96 of +1 and -1 and compare meter readings to see if I can get my camera to duplicate what you've discovered. If you get a chance, maybe you can set the camera to manual exposure mode, and set the shutter to 1 second. Find a relatively dark, constant lit scene (closet?), and pick an aperture and ISO so the exposure looks right.  Then set CHDK to save dng raw files, and take a picture with one notch (1/3 ev?) above 1 second and 1 below. Then, compare the 2 jpg and 2 dng files. I suspect the jpgp files will be similar, but the dng files will have much different brightness.

The regular oscillations in brightness come from the difference in meter readings over and under one second shutter time. Apparently, this difference is a constant.
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 #397 on: 04 / September / 2013, 18:51:51 »
I caught a really pretty sunset last night with the G1X:
http://www.youtube.com/watch?v=utGA60nspfo#

I also set up the SX50 at the same spot, zoomed in on the paper mill with a 2nd meter just on the tower that lights up the brightest at night. This meter took over after dark and kept the right exposure for the tower. Usually, lighted buildings are overexposed in night shots. I had the tripod extension tube up, so touching the camera buttons caused some shaking with the high zoom setting.
http://www.youtube.com/watch?v=_kZqszU6FMQ#

I tried out a wide angle lens attachment on the G1X. It clips the corners (extreme vignetting) unless you zoom in a little, which kind of defeats the purpose of the wide angle lens. So I left the clipped corners on the bottom and cropped the top so I could see the widest area of sky possible.  It's a pretty interesting effect.
http://www.youtube.com/watch?v=nQuEBx0vF7Q#

This uses the wide angle lens, but zoomed until the vignetting isn't obvious:
http://www.youtube.com/watch?v=K-Ri0xQf714#
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 #398 on: 05 / September / 2013, 15:34:29 »
I'm really beginning to like the Canon D20 for sunsets. The simple lens has fewer lens reflection with the sun in the frame. I was able to crop the single lens reflection out of this video, except for a short time at the beginning. Pointing at the sun, the camera starts with the ND filter in, and it was able to expose the sun correctly so it's a circle instead of the usual blown out area.

Once I add ND filter control, I should be able to go smoothly to total darkness with stars showing using the D20. Here's a photo and the time lapse video I took last night from the top of Spencer's Butte with the D20.



http://www.youtube.com/watch?v=jUAeO3LctT8#
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 #399 on: 08 / September / 2013, 12:55:30 »
I've been trying out my time lapse script after dark lately. I used it to capture an Iridium flare the last two nights.

The first picture shows the Iridium flare I captured 2 nights ago with the G1X. It's a 5 second exposure at 1600 ISO. Unfortunately, the flare ended up split between two pictures. I stacked the pictures together but there's still a gap in the flare between shots.

So last night I set the maximum shutter time to 25 seconds and captured the entire flare in one shot. Then I noticed that there was another, dim "flare" about 2 minutes before the Iridium flare that only appeared in one frame. It must be another satellite that also caught the glint of the sun so it got a little brighter and became visible.
EOS-M3_120f / SX50_100b / SX260_101a / G1X_100g / D20_100b
https://www.youtube.com/user/DrLapser/videos

 

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