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Using CHDK in PowerShot S95

I bought an older type "PowerShot S95" at the last bargain sale.
And I use CHDK (Canon Hack Development Kit) with S95.
In Japanese page, I explain about how to use CHDK,
because there are only few Japanese information about CHDK, and they are difficult for me to start.
For example, no one explain about to push shutter button after setting to move shooting mode.
On the other hand, there are many information in English web site, and I can start to use CHDK by them.
Then, for Japanese people, I show some information.
Though they would be no meaning for English reader, then I translate except how to use.
I select two items.
1. Measuring the actual shutter speed limit of S95 with CHDK
2. Some of focus stacking information

1. Measuring the actual shutter speed limit of S95 with CHDK
I made a ring counter circuit by using two 4017 to lid 100 of LED,
and shot this.
The LED lid from left to right and go down to next line. And right down end to left top start again.



The first photo shot 100kHz blinking LED by 1/1600 setting without CHDK.



87 LED exposed.
Then the shutter speed value is between 85/100k and 87/100k.
It means between 1/1176 and 1/1149. The actual speed seems less than set value 1/1600.
I'm not sure why one LED is lid a little before, though every time like this.

The next photo shot 300kHz blinking LED by 1/40k setting with CHDK.



The actual shutter speed limit with CHDK is 66/300k...68/300k (=1/4545...1/4412).

2. Some of focus stacking information
I don't translate about how to use bracketing in continuous mode here.
I translate about the point of consideration of focus stacking inside the camera.

One way to calculate focus stacking is as follows.
Shoot some of same flame photo by different focus.
Multiple contrast factor for each pixel data.
(The contrast factor means the difference from the next pixel.)
Calculate average of all photos for each pixel.
For extreme example, contrast factor is one,
it means that only calculate average of all photos for each pixel,
you can get a focus stacking even though it will be a lower contrast.
There are many contrast effect in the camera,
then some effect may be effective as a multiple contrast factor.
Though S95 seems not suit for this use, because
the pixel average calculation seems to able only at RAW data that is
large file and without correction at surrounding area.
Though I can find some explanation as " by combining several continuous shots" in S100 manual.
Then S100 may be able to make focus stacking inside the camera by using CHDK.
I expect to CHDK hacker to achieve a real time focus stacking inside the camera.

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