supplierdeeply

Setting Shutter speed,ISO and focus on Canon SX170IS

  • 4 Replies
  • 1021 Views
Setting Shutter speed,ISO and focus on Canon SX170IS
« on: 08 / August / 2015, 10:16:54 »
Advertisements
Hi everyone,

I am able to change ISO,shutter speed and focus values using LUA script. I am using set_sv96() , set_tv96_direct() and set_focus() functions respectively to change values but I am not sure about what I am doing is right or not.

1)I have read chdk docs and been confused about exactly what to change in menu `Enhanced Photo Operations` if I override something does this means that whatever the value I send with script is overridden or overriding enables me to override original camera values with those that I send with script commands.This is the first matter that I want to be sure .

2) There are variety of functions for sv and tv ( I mean market value,set direct like names) . What are the best functions to be used?

3) When I change focus from 0 to some value the photo is blurred or when I change iso the picture is being close to constant white bright image and finally I could not get any difference if I change the shutter speed with set_tv96_direct() . Am I doing something wrong ? What value range should I use for each property ?

Can anyone help me because the more I read guides the more I am getting confused . Thanks in advance for any help

Re: Setting Shutter speed,ISO and focus on Canon SX170IS
« Reply #1 on: 08 / August / 2015, 10:48:29 »
1)I have read chdk docs and been confused about exactly what to change in menu `Enhanced Photo Operations` if I override something does this means that whatever the value I send with script is overridden or overriding enables me to override original camera values with those that I send with script commands.This is the first matter that I want to be sure .
You can override the exposure settings that Canon will use ( shutter speed, aperture, ISO, ND filter) using either the CHDK `Enhanced Photo Operations` menu or with a CHDK script.  Either will work but if you try to do both at the same time,  the settings specified by the script will be used.

Note that when you change an exposure value, the Canon firwmare does not know you have done that.  It assumes its value is being used and it sets all the other values based on that assumption.   So you really need to set all four values (Tv, Av, Sv, ND filter) if you want the resulting exposure to be correct.   (Note : many Canon P&S cameras do not have an adjustable aperture - the f-stop value used depends only on the zoom position.  Also, some cameras do not have a built-in ND filter).

Quote
2) There are variety of functions for sv and tv ( I mean market value,set direct like names) . What are the best functions to be used?
Like most things in CHDK, the answer to that question is "It depends on what you are trying to do".

ISO market vs ISO real has been the topic of dicussion on this forum for years.  You can google it for yourself but here's a couple of links :
http://chdk.wikia.com/wiki/CHDK_firmware_usage/AllBest#Show_.27Real.27_ISO
http://chdk.setepontos.com/index.php?topic=10341.0
http://chdk.wikia.com/wiki/Script_commands#APEX96_Conversion_Functions

As far as Tv settings go,  at a small risk of oversimplifying,  just use set_tv96_direct.

Quote
3) When I change focus from 0 to some value the photo is blurred or when I change iso the picture is being close to constant white bright image and finally I could not get any difference if I change the shutter speed with set_tv96_direct() . Am I doing something wrong ? What value range should I use for each property ?
Focus settings are in millimeters.   If you don't set the focus value to the correct distance then you will get blurry pictures.

I'm not sure what you are describing with you ISO question.  Please post the script as an attachment to your reply and I can take a closer look.  It could be a scripting error or it could be you asking CHDK to do something that it can't.  Or you might be seeing exactly what you would expect to see given what you have asked CHDK to do.
« Last Edit: 08 / August / 2015, 10:53:22 by waterwingz »
Ported :   A1200    SD940   G10    Powershot N    G16

Re: Setting Shutter speed,ISO and focus on Canon SX170IS
« Reply #2 on: 08 / August / 2015, 11:19:54 »

You can override the exposure settings that Canon will use ( shutter speed, aperture, ISO, ND filter) using either the CHDK `Enhanced Photo Operations` menu or with a CHDK script.  Either will work but if you try to do both at the same time,  the settings specified by the script will be used.

Note that when you change an exposure value, the Canon firwmare does not know you have done that.  It assumes its value is being used and it sets all the other values based on that assumption.   So you really need to set all four values (Tv, Av, Sv, ND filter) if you want the resulting exposure to be correct.   (Note : many Canon P&S cameras do not have an adjustable aperture - the f-stop value used depends only on the zoom position.  Also, some cameras do not have a built-in ND filter).

So it is okay to only set `disable overrides` and `disable overrides on startup` to no or unchecked if I want only change values through script commands.

Re: Setting Shutter speed,ISO and focus on Canon SX170IS
« Reply #3 on: 08 / August / 2015, 11:20:49 »

I'm not sure what you are describing with you ISO question.  Please post the script as an attachment to your reply and I can take a closer look.  It could be a scripting error or it could be you asking CHDK to do something that it can't.  Or you might be seeing exactly what you would expect to see given what you have asked CHDK to do.

I am using set_sv96(x) function to change iso value. What are the valid minimum and maximum values of x I should use.
« Last Edit: 08 / August / 2015, 11:30:47 by simtek »


Re: Setting Shutter speed,ISO and focus on Canon SX170IS
« Reply #4 on: 08 / August / 2015, 13:02:34 »
So it is okay to only set `disable overrides` and `disable overrides on startup` to no or unchecked if I want only change values through script commands.
Yes

I am using set_sv96(x) function to change iso value. What are the valid minimum and maximum values of x I should use.
You can't really extent the normal range of ISO sensitivity values offered by the camera (or at least not much).  So you are looking at values between ISO80 and ISO1600 ( ISO3200 on some cameras ).

I've attached a little Lua script you can run to test different values.   It will show you that for a Canon ISO 80 value, the sv96 value is 381 and for ISO 1600 the sv96 value is 795.
Ported :   A1200    SD940   G10    Powershot N    G16

 

Related Topics