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a590 iso

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Offline shinnen

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a590 iso
« on: 10 / October / 2017, 14:15:32 »
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Hi all,
         I have my a590 set to iso 30. (I doubt the camera will achieve this, but I want the lost possible iso.) The question is .... by setting it at iso 30, am I achieving the lowest possible iso that the camera is capable of, or will the camera ignore my setting and choose some other iso setting?
Thanks,
...... john
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Offline waterwingz

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Re: a590 iso
« Reply #1 on: 10 / October / 2017, 15:36:44 »
Quote from: shinnen on 10 / October / 2017, 14:15:32
I have my a590 set to iso 30. (I doubt the camera will achieve this, but I want the lost possible iso.) The question is .... by setting it at iso 30, am I achieving the lowest possible iso that the camera is capable of, or will the camera ignore my setting and choose some other iso setting?

AFAIK, when you set it to something really low it will lock at the lowest actual limit.   But you could run a test just like you did for fast shutter speeds to confirm that..
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Offline shinnen

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Re: a590 iso
« Reply #2 on: 10 / October / 2017, 16:43:01 »
Thanks.
Yes, I might do that.
.... john
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Offline reyalp

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Re: a590 iso
« Reply #3 on: 11 / October / 2017, 00:10:34 »
You can use the isoinc script I wrote to test this https://chdk.setepontos.com/index.php?topic=12165.msg127110#msg127110

One could write a similar script to test shutter overrides. That would give a more quantitative idea of how accurately the override works than just looking at images.
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Offline shinnen

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Re: a590 iso
« Reply #4 on: 11 / October / 2017, 10:39:40 »
Hi reylap,
       I tried the isoinc script on my a590. I presume the isoinc.csv is where I find the results; but I can't make head nor tail of it. Should I have deactivated the CHDK iso preset value. I had it set at 30?
       I'm not particularly interested in quantifying the shutter speed, any closer than eye balling the series of shot tell me. I was just looking for a ball park figure. Can I assume that the script would just give me a more precise value, in the same range as what I found from the images?
Thanks,
..... john
       
       
     
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Offline reyalp

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Re: a590 iso
« Reply #5 on: 11 / October / 2017, 17:02:39 »
Quote from: shinnen on 11 / October / 2017, 10:39:40
Hi reylap,
       I tried the isoinc script on my a590. I presume the isoinc.csv is where I find the results; but I can't make head nor tail of it. Should I have deactivated the CHDK iso preset value. I had it set at 30?
The CHDK ISO override shouldn't matter. Some instructions for the script are in the first post of the thread: https://chdk.setepontos.com/index.php?topic=12165.msg120951#msg120951

Basics:
Put the camera on a stable surface and point it something neutral and unchanging, like a wall.
Set the start value and end value to the ISO range you want to test. (e.g. 30 and 100 if you wan to test the low end)
Set ISO input to type to ISO
Set the shooting mode to "Quick"

Other options can probably be left at the default.

If you do this, then plotting m96 (the average value of the image in exposure-like units) should give you a diagonal line over the range where ISO override works, and a horizontal line where it doesn't. Or you can just post the csv here ;)

Quote
       I'm not particularly interested in quantifying the shutter speed, any closer than eye balling the series of shot tell me. I was just looking for a ball park figure. Can I assume that the script would just give me a more precise value, in the same range as what I found from the images?
If an exposure to really works (rather than just having some effect), X "stops" of override (say going from 1/4096 to 1/8192 for one stop) must give X "stops" of exposure change in the resulting image. This can be found by measuring the raw values at different exposures, which is what isoinc does.

For shutter overrides, you should also check a couple of other things:
* How much variation there is between shots with the same override value.
* Is the exposure consistent over the image? At very short exposures, it's possible different parts of the sensor aren't exposed for the same amount of time.

edit:
I should add I"m not saying need to do any of this, I'm just explaining how I would do it.
« Last Edit: 11 / October / 2017, 17:10:15 by reyalp »
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Offline shinnen

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Re: a590 iso
« Reply #6 on: 12 / October / 2017, 19:40:26 »
Hi reyalp,
        Thank you for your help. I'm not sure I did this right, and I may have overdone it.
I set it for iso 10 to iso 200.
Here's the content of the isoinc file .... yikes!
..... john

date,tick,exp,vbatt,tsensor,topt,free_mem,lua_mem,sd_space,sv,sv96,p_sv,p_sv_market,p_delta_sv,p_delta_sv_next,p_iso_mode,tv,tv96,av,av96,meter,meter96,desc
10/12/2017 19:27:05,80730,523,2409,35,26,468728,90,657664,75,371,371,480,-40,,0,0.010428,632,4.490,416,32,-693,platform:a590-101b-1.5.0-4747 Dec 20 2016 01:45:08 / shoot_mode=single / iso_method=chdk / start tv96=312 sv96=243 ev_shift=-2 / black_level:31
10/12/2017 19:27:11,86790,524,2409,36,26,466184,92,646976,75,372,372,480,-39,,0,0.010428,632,4.490,416,32,-693,
10/12/2017 19:27:17,92530,525,2409,36,26,464528,93,636320,76,373,373,480,-38,,0,0.010428,632,4.490,416,32,-693,
10/12/2017 19:27:23,98280,526,2405,36,26,462832,95,625664,77,374,374,480,-37,,0,0.010428,632,4.490,416,32,-693,
10/12/2017 19:27:29,104020,527,2405,36,26,461216,96,615008,77,375,375,480,-36,,0,0.010428,632,4.490,416,32,-693,
10/12/2017 19:27:34,109780,528,2405,37,26,459544,98,604304,78,376,376,480,-35,,0,0.010428,632,4.490,416,32,-693,
10/12/2017 19:27:40,115700,529,2401,37,26,457904,99,593584,78,377,377,480,-34,,0,0.010428,632,4.490,416,32,-693,
10/12/2017 19:27:46,121440,530,2401,37,26,456264,100,582864,79,378,378,480,-33,,0,0.010428,632,4.490,416,32,-693,
10/12/2017 19:27:52,127210,531,2405,37,26,454640,102,572176,79,379,379,480,-32,,0,0.010428,632,4.490,416,32,-693,
10/12/2017 19:27:57,132990,532,2401,37,26,452968,103,561456,80,380,380,480,-31,,0,0.010428,632,4.490,416,32,-693,
10/12/2017 19:28:03,138750,533,2401,37,27,454400,101,550720,81,381,381,480,-30,,0,0.010428,632,4.490,416,32,-693,
10/12/2017 19:28:09,144520,534,2401,38,27,455672,101,539984,81,382,382,480,-29,,0,0.010428,632,4.490,416,32,-693,
10/12/2017 19:28:15,150300,535,2401,38,27,484592,75,529248,82,383,383,480,-28,,0,0.010428,632,4.490,416,32,-693,
10/12/2017 19:28:21,156040,536,2401,38,27,482968,77,518496,82,384,384,480,-27,,0,0.010428,632,4.490,416,32,-693,
10/12/2017 19:28:27,162030,537,2401,38,27,481320,78,507792,83,385,385,480,-26,,0,0.010428,632,4.490,416,32,-693,
10/12/2017 19:28:32,167780,538,2396,38,27,479680,80,497088,83,386,386,480,-25,,0,0.010428,632,4.490,416,32,-693,
10/12/2017 19:28:38,173560,539,2396,38,27,478088,81,486336,84,387,387,480,-24,,0,0.010428,632,4.490,416,32,-693,
10/12/2017 19:28:44,179330,540,2396,38,27,476400,82,475568,85,388,388,480,-23,,0,0.010428,632,4.490,416,33,-597,
10/12/2017 19:28:50,185100,541,2401,38,27,474784,84,464800,85,389,389,480,-22,,0,0.010428,632,4.490,416,33,-597,
10/12/2017 19:28:55,190870,542,2401,38,27,473152,85,454032,86,390,390,480,-21,,0,0.010428,632,4.490,416,33,-597,
10/12/2017 19:29:01,196650,543,2396,38,27,471520,87,443248,87,391,391,480,-20,,0,0.010428,632,4.490,416,33,-597,
10/12/2017 19:29:07,202420,544,2396,39,27,469880,88,432528,87,392,392,480,-19,,0,0.010428,632,4.490,416,33,-597,
10/12/2017 19:29:13,208190,545,2396,39,27,468240,90,421760,88,393,393,480,-18,,0,0.010428,632,4.490,416,33,-597,
10/12/2017 19:29:18,213960,546,2392,39,27,468872,88,410976,88,394,394,480,-17,,0,0.010428,632,4.490,416,33,-597,
10/12/2017 19:29:24,219740,547,2392,39,27,470072,88,400192,89,395,395,480,-16,,0,0.010428,632,4.490,416,33,-597,
10/12/2017 19:29:30,225520,548,2392,39,27,484640,75,389440,90,396,396,480,-15,,0,0.010428,632,4.490,416,33,-597,
10/12/2017 19:29:36,231320,549,2396,39,27,483040,77,378688,90,397,397,480,-14,,0,0.010428,632,4.490,416,33,-597,
10/12/2017 19:29:42,237100,550,2392,39,27,481392,78,367936,91,398,398,480,-13,,0,0.010428,632,4.490,416,33,-597,
10/12/2017 19:29:47,242870,551,2396,39,27,479736,80,357168,92,399,399,480,-12,,0,0.010428,632,4.490,416,33,-597,
10/12/2017 19:29:53,248660,552,2392,39,27,478128,81,346368,92,400,400,480,-11,,0,0.010428,632,4.490,416,33,-597,
10/12/2017 19:29:59,254470,553,2392,39,27,476488,82,335568,93,401,401,480,-10,,0,0.010428,632,4.490,416,33,-597,
10/12/2017 19:30:05,260240,554,2392,39,27,474840,84,324768,94,402,402,480,-9,,0,0.010428,632,4.490,416,33,-597,
10/12/2017 19:30:11,266060,555,2392,39,27,473216,85,313952,94,403,403,480,-8,,0,0.010428,632,4.490,416,33,-597,
10/12/2017 19:30:16,271850,556,2392,39,27,471568,87,303136,95,404,404,480,-7,,0,0.010428,632,4.490,416,33,-597,
10/12/2017 19:30:22,277620,557,2392,39,27,469960,88,292320,96,405,405,480,-6,,0,0.010428,632,4.490,416,33,-597,
10/12/2017 19:30:28,283380,558,2388,39,28,468336,90,281472,96,406,406,480,-5,,0,0.010428,632,4.490,416,33,-597,
10/12/2017 19:30:34,289130,559,2392,40,28,469160,88,270640,97,407,407,480,-4,,0,0.010428,632,4.490,416,33,-597,
10/12/2017 19:30:39,294910,560,2392,40,28,470200,88,259808,98,408,408,480,-3,,0,0.010428,632,4.490,416,33,-597,
10/12/2017 19:30:45,300910,561,2392,40,28,484544,75,248960,99,409,409,480,-2,,0,0.010428,632,4.490,416,33,-597,
10/12/2017 19:30:51,306700,562,2392,40,28,482928,77,238112,99,410,410,480,-1,,0,0.010428,632,4.490,416,33,-597,
10/12/2017 19:30:57,312500,563,2388,40,28,481336,78,227232,100,411,411,480,0,,0,0.010428,632,4.490,416,33,-597,
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Offline reyalp

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Re: a590 iso
« Reply #7 on: 13 / October / 2017, 03:45:59 »
Quote from: shinnen on 12 / October / 2017, 19:40:26
Hi reyalp,
        Thank you for your help. I'm not sure I did this right, and I may have overdone it.
I set it for iso 10 to iso 200.
In the future, I'd suggest using the file attachment option (visible after you click "reply" or preview)

In your log, the "meter" values is very near black level, so it was too under-exposed to measure anything. I forgot to mention this in the earlier post, but the camera should be in P mode with CHDK overrides off, so it can start with a reasonable exposure.
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Offline shinnen

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Re: a590 iso
« Reply #8 on: 13 / October / 2017, 09:16:47 »
Hi reyalp,
         OK....... attach file ...... got it.
Alright. I'll try it again as suggested.
Thanks,
...... john
P.S. I thought it was odd when I couldn't see anything; but ignored that because I wasn't sure the script didn't shut of the image somehow.
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Offline shinnen

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Re: a590 iso
« Reply #9 on: 13 / October / 2017, 09:44:19 »
Hi reyalp,
          Have a look at this one (attached). I changed it to iso20 to iso200
...... john
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