G7 Slow Continuous Shooting Speed at High ISO

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Just got the G7 and was surprised to find out that you can't use 2 fps shooting above ISO 200.  I called Canon support tonight and they had the same problem.   The best fps using ISO 400-1600 is about 1.0 fps (half of what Canon states).  By the way I am not using the AF continuous mode (that is only 0.8 fps).   I have tried MF  / exposure lock / lower res. files.  Just thought those looking to purchase this camera should know about this limitation.

[Ray]

You should be aware that on all cameras, high ISO shots result in bigger RAW files and more processing. The G7 doesn't allow you access to RAW files but it certainly produces RAW files which are processed and converted in-camera.

A RAW file on my Canon 5D can range from 11mp to 16 mp, depending on the complexity of the scene and the ISO setting.

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You should be aware that on all cameras, high ISO shots result in bigger RAW files and more processing. The G7 doesn't allow you access to RAW files but it certainly produces RAW files which are processed and converted in-camera.

A RAW file on my Canon 5D can range from 11mp to 16 mp, depending on the complexity of the scene and the ISO setting.
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Does your 5D reduce its shooting speed when shooting at high ISO?  I have an A75 that shoots faster than the G7 at ISO 400.   I know the files are not of the same quality but the G7 is the top of the line P&S not an A series.  I guess I expect a G series camera to perform better.  I realize that there is more processing going on when shoooting with high ISO, but Canon does not state that 2 fps is only available at ISO 80-200.

[Henrik Paul]

I'd imagine the slower shooting speeds on high ISO:s, especially when shooting with high-quality JPEG:s, is that the processor takes a longer time trying its best analysing the noisy image, trying to save each detail as well as possible. Nevertheless, this seems like yet another compromise/bad choice on Canon's part. It would be interesting to know whether this is a global issue.

Try lowering the JPEG quality and see if it has an effect on performance.

On the contrary to what Ray here claims, noise levels on raw (wonder who invented the capitalization of the word) images don't automatically affect the file size nor the processing time (since the image size is constant, noise or not). This becomes an issue only when the image is further compressed (which, in theory, could result in a lowered performance). Compression of raw-images hasn't been around for very long execpt for the high-end DSLR:s.

[Ray]

On the contrary to what Ray here claims, noise levels on raw (wonder who invented the capitalization of the word) images don't automatically affect the file size nor the processing time (since the image size is constant, noise or not). [a href=\"index.php?act=findpost&pid=95076\"][{POST_SNAPBACK}][/a]

The converted file size is not affected, of course, but the RAW file size is all over the place. I have assumed the reason is due to a variation in the degree of lossless compression that can be applied to a particular image, and that that degree of compression is affected by the complexity of the scene and the additional complexity of processing a noisy image. For example, right at the moment my 5D tells me I have 135 images left on my CF card. ISO is set to 100. I set the ISO to 400 and the available images drops to 128. I set the camera to ISO 1600 and the available number of images drops to 118. I set the camera to ISO 3200 and the available images drops further to just 108. My camera is of course set on RAW mode. This seems to me fairly conclusive that ISO affects RAW file size.

In the case of the G7, it seems Canon have pulled out all the stops to get a usable image at high ISOs. They are so proud of what they've achieved, they've even denied the consumer the privilege of accessing the RAW files themselves, possibly because they don't believe there's much improvement to be gained.

It seems quite understandable to me that the G7 will slow down at high ISOs. There's a lot of processing going on in that little camera.

[Jonathan Wienke]

On the contrary to what Ray here claims, noise levels on raw (wonder who invented the capitalization of the word) images don't automatically affect the file size nor the processing time (since the image size is constant, noise or not). This becomes an issue only when the image is further compressed (which, in theory, could result in a lowered performance).

Raising the ISO increases the noise level, which will significantly increase the JPEG file size and/or the processing time required to remove it. The exact same information-theory principles that cause RAW file size to vary apply to JPEG size as well. The only time file size is constant is when either no compression is applied, or the compression level is varied specifically to achieve a specific output size.

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Raising the ISO increases the noise level, which will significantly increase the JPEG file size and/or the processing time required to remove it. The exact same information-theory principles that cause RAW file size to vary apply to JPEG size as well. The only time file size is constant is when either no compression is applied, or the compression level is varied specifically to achieve a specific output size.
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I just want to know why my A75 takes photos faster than my G7 at ISO 400 (I did the test at full res. on both cameras).  I even took the G7 down to 640x480 res. (to reduce file size) with the same results.   I know the high ISO photos from the A75 are nowhere near the quality of the G7.  The G7 must do more processing at 400 and above.  

My main problem is that Canon does not say anything about this limitation.  I think anyone buying a DSLR that had a similar limitation would have a problem.  When a company says 2 fps the camera should perform at that level no matter what the ISO.  Does anyone think this is an unreasonable expectation?