Powershot S5 - faster than 1.5 fps

[kinematic]

I made an interesting discovery the last couple of days. It was sparked by this conversation:

Flickr: Discussing SD Card Question in Canon PowerShot S5  IS

I'm able to get almost 2 frames per second shooting on the S5 which is rated for 1.5 fps. I've done probably over a 1000 test shots to narrow it down.

It appears to be software related so I'm wondering if this might be something that CHDK can work around. I know that we can shoot video at 30 fps, but video is just pulling images from the sensor directly like the LCD screen, however that said, is it possible for CHDK to capture images at a higher rate?

I've isolated the following parameters that seems to get the extra fps.

Tv or P mode
Shutting off Safety Shift
Turning down image size to M2 or less
Must be in the Digital Zoom (standard for 1.93333 fps, tele 2.0 for 1.7 fps)

I also think you need at least a Class 4 SD card

Thoughts?

[RaduP]

Video doesn't read the whole sensor, it only reads 1 out of 3 lines or something. To read the full sensor you need to use the shutter.
The video, having a smaller resolution, is faster to compress as well. I seriously doubt that Canon limited the speed in software.

[vit40]

According to pdf from Sony, sensor (ICX 636/646) is able to produce 2.5 fps in frame readout mode

[kinematic]

Video doesn't read the whole sensor, it only reads 1 out of 3 lines or something. To read the full sensor you need to use the shutter.
The video, having a smaller resolution, is faster to compress as well. I seriously doubt that Canon limited the speed in software.

That's what I thought too RaduP. However that said, only going down two resolution+Digital Zoom settings helps speeds things up. The theory based on this would be to just turn it to 640 x 480 should speed things up, but that doesn't do a thing. It has to be the combination of two resolution steps down and the digital zoom. It doesn't really make any sense at all. I do know that the Safety Shift is an auto setting that affects the shutter speed, so it makes sense that shutting that off reduces any lag. Regardless I'm still managing to get 25% more shots than what the Canon marketing has reported.

[RaduP]

According to pdf from Sony, sensor (ICX 636/646) is able to produce 2.5 fps in frame readout mode

Yes, but you also have to process and write the image as well, which can be slow and it depends on many factors (resolution, compression rate, memory card speed, etc.)

[grg]

It has to be the combination of two resolution steps down and the digital zoom. It doesn't really make any sense at all.

check out the excellent documentation for fudgey's fast MD script:
http://chdk.setepontos.com/index.php/topic,471.msg17797.html#msg17797

    Tip:  For the highest possible burst rate (photos per second),
      * Disable RAW.
      * Use a fast shutter speed (Tv).
      * Do not use ISO 200 or higher (camera will spend time applying
        some noise reduction filtering).
      * Use a sufficiently fast SD card and keep it defragmented by
        full erase as often as you find convenient.
      * Enable the digital telephoto feature and choose the one and only
        JPEG image size for which the camera doesn't need to resize
        the photo (for a570is 1,9x digital telephoto this means 1600x1200).
        At least on the a570is the digital telephoto feature is marked
        with a "T" symbol on the LCD, and the optimum JPEG resolution
        can be found by decreasing JPEG resolution setting until the "T" symbol
        is no longer blue. Note that reducing JPEG resolution further (or
        without the digital telephoto feature) will slow down the burst
        because the camera will have to resize the image (unless your SD card
        is very slow). Your camera may not have this feature.

I haven't made any speed tests, but my A640 has these blue/white "T"s too.  Max image size is 3648x2736, with 2,3x digital zoom it matches 1600x1200 too, so the image would just need to be cropped, not resized.

[cybercom]

Video doesn't read the whole sensor, it only reads 1 out of 3 lines or something. To read the full sensor you need to use the shutter.
The video, having a smaller resolution, is faster to compress as well. I seriously doubt that Canon limited the speed in software.

I'd be interested to know where you got this information from.

[dzsemx]

this lineskip mode is used for preview too... no difference
almost every ccd's have this mode...
without this you could't have live preview and video mode with 30 fps
smaller resolutions are made with downscale
there is electronic shutter for each frame without mechanical shutter... the charge transfer without mech shutter causes vertical lines on the screen when pointing the camera to a brigth object like a bulb
line skipping causes also strong moire when pointing camera to almost horizontal lines
and yes, digital zoom speeds up things because the readout circuit drops the half of the lines

[fudgey]

You may also want to see this thread for earlier discussion about burst rates:
http://chdk.setepontos.com/index.php/topic,1864.0.html.

[dzsemx]

3 sony ccd sensors (icx612 is used in a650) with 3 different readout modes:
http://www.sony.net/Products/SC-HP/cx_news/vol49/pdf/icx636_646.pdf

[dzsemx]

btw the sony news can be found here: Sony Global - CX-NEWS