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Using SD Override from Main Menu.

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Offline stagdriver

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Using SD Override from Main Menu.
« on: 30 / March / 2014, 14:57:11 »
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Hi i tested my a470 and a2300 today and found something odd regarding the set values.
It seems both cameras can accept an input in mm up to around 200mm and the results are oretty pecuse.
However as you start to roan above 300 the output focus is always lager than whats input.
for example input 225mm on an a2300 and the focus is actually about 300mm
Input 280mm and the focus is 700mm, 350mm in and 1metre out. 1000mm in and 3000 out etc.
The a470 seems to behave similarly.
The zoom is at zero (any increase in zoom dramatically alters the results.
Is this a known issue being camera dependant.
Are there any threads i could be directed to. All my searches take me to sd override in script.
regards
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Offline waterwingz

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Re: Using SD Override from Main Menu.
« Reply #1 on: 30 / March / 2014, 15:09:49 »
Quote from: stagdriver on 30 / March / 2014, 14:57:11
Hi i tested my a470 and a2300 today and found something odd regarding the set values.
It seems both cameras can accept an input in mm up to around 200mm and the results are oretty pecuse.
However as you start to roan above 300 the output focus is always lager than whats input.
for example input 225mm on an a2300 and the focus is actually about 300mm
Input 280mm and the focus is 700mm, 350mm in and 1metre out. 1000mm in and 3000 out etc.
The a470 seems to behave similarly.
The zoom is at zero (any increase in zoom dramatically alters the results.
Is this a known issue being camera dependant.
Are there any threads i could be directed to. All my searches take me to sd override in script.
regards
More SD override mysteries.   I noticed my really old A560 (purchased used & abused) is even more inaccurate than what you report but I put that down to its old age.   I'll do some testing on my newer cameras.
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Ported :   A1200    SD940   G10    Powershot N    G16
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Online reyalp

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Re: Using SD Override from Main Menu.
« Reply #2 on: 30 / March / 2014, 15:22:13 »
Quote from: stagdriver on 30 / March / 2014, 14:57:11
Hi i tested my a470 and a2300 today and found something odd regarding the set values.
It seems both cameras can accept an input in mm up to around 200mm and the results are oretty pecuse.
However as you start to roan above 300 the output focus is always lager than whats input.
for example input 225mm on an a2300 and the focus is actually about 300mm
Input 280mm and the focus is 700mm, 350mm in and 1metre out. 1000mm in and 3000 out etc.
The a470 seems to behave similarly.
The zoom is at zero (any increase in zoom dramatically alters the results.
Is this a known issue being camera dependant.
Are there any threads i could be directed to. All my searches take me to sd override in script.
regards
While this certainly could be a problem with CHDK, it could also just be the focus steps the camera actually implements. These cameras have a very large depth of field, once you get out of the extreme closeup, there really isn't a need for a lot of focus steps.

If either of these cameras have MF, you could try adjusting it there and see what CHDK reports as the focus distance.
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Offline stagdriver

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Re: Using SD Override from Main Menu.
« Reply #3 on: 30 / March / 2014, 17:24:06 »
Thanks Waterwingz and Reyalp for the responses. Out of 7 different cameras available it seems that i only have 2 that can truly manually focus. An  A530 and a550.

From what you say Reyalp, i'm guessing that if i manually focus onto 'an item' on my focus test range ( a plank of wood with numbered pegs at set distances with a detailed target pattern) then swap into chdk without turning the camera off first, and then view the numbers displayed in the "overide subject distance () the numbers should be the focus value ?? ( i had noticed they seemed to change but was not aware why).

If this is the case i can make a matrix card to accurately set my focusing  to reasonable levels (i'm thinking that this should also be possible for the other cameras without manual focus, by focusing onto the desired target with a 1/2 button press, then swapping into chdk and viewing the numbers??......All sounds too easy.

I shall try this tomorrow and post any meaningful results.
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Offline waterwingz

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Re: Using SD Override from Main Menu.
« Reply #4 on: 30 / March / 2014, 17:29:47 »
Quote from: stagdriver on 30 / March / 2014, 17:24:06
From what you say Reyalp, i'm guessing that if i manually focus onto 'an item' on my focus test range ( a plank of wood with numbered pegs at set distances with a detailed target pattern) then swap into chdk without turning the camera off first, and then view the numbers displayed in the "overide subject distance () the numbers should be the focus value ?? ( i had noticed they seemed to change but was not aware why).

If this is the case i can make a matrix card to accurately set my focusing  to reasonable levels (i'm thinking that this should also be possible for the other cameras without manual focus, by focusing onto the desired target with a 1/2 button press, then swapping into chdk and viewing the numbers??......All sounds too easy.
It's actually a bit easier than that.  You can have the SD value displayed all the time (even when you are not in CHDK <ALT> mode).  In OSD Settings -> DOF Calculator menu, just set the  Show DOF Calculator to  [ In Misc ]  and in the Miscellaneous Values menu set Show Misc Values  to [  Always ]
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Ported :   A1200    SD940   G10    Powershot N    G16
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Offline stagdriver

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Re: Using SD Override from Main Menu.
« Reply #5 on: 30 / March / 2014, 17:33:03 »
Thanks Waterwingz, it ie that easy.
I will Produce a chart tomorrow.
Fortunately i have 2 identical A470's so i will repeat the test and see if there is some level of repeatability.
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Offline waterwingz

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Re: Using SD Override from Main Menu.
« Reply #6 on: 30 / March / 2014, 17:34:45 »
Quote from: stagdriver on 30 / March / 2014, 17:33:03
Thanks Waterwingz, it ie that easy.
I will Produce a chart tomorrow.
Fortunately i have 2 identical A470's so i will repeat the test and see if there is some level of repeatability.
You'll probably also find that once you are more than a meter or two out, everything is in focus.
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Ported :   A1200    SD940   G10    Powershot N    G16
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Offline stagdriver

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Re: Using SD Override from Main Menu.
« Reply #7 on: 31 / March / 2014, 10:43:25 »
You are on the money regarding focus around 1-2 metres being infinity.
I ended up testing three cameras
1 A470
2 A550
3 A2300
Turned out to be very different animals altogether.

The A470 turned out to follow a rising exponential curve (pretty much).
the A550 was pretty much accurate.
the A2300 was pretty linear but trending away from the desired focus the bigger the distance was

i have attached the graphs for A470 and A2300 for info.

I have used these to select the SD values for my desired focal distance and they have been spot on during my tests. (Incidentally, my second A470 was pretty much identical to my first)

So looks like the SD numbers are pretty much hardware dependant and may vary a lot. If you like to use them for closer subjects i suggest conducting the test and creating a chart specific to your own camera in order to reduce the dissapointments.
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