SX50: thoughts on digital zoom

Started Jun 17, 2013 | Discussions thread
OP Don_Campbell Senior Member • Posts: 2,735
Re: SX50: thoughts on digital zoom

gardenersassistant wrote:

An interesting comparison and conclusions. Thanks for taking the time to document your experiment and conclusions.

I have been working along somewhat similar lines with my SX240. I am now using CHDK to capture RAW + JPEG.

I use digital zoom for framing shots beyond the 20x optical limit of the SX240 (500mm equivalent focal length), but then do the crop myself from the RAW version, which covers the 20x optical area irrespective of the amount of digital zoom. This means, like you point out, being able to see what is going on better, especially as you move further beyond the optical limit. Also, the precise framing of the image is very important for my visual preferences (usually involving flowers when using the SX240), and using digital zoom lets me see how the framing will look rather than having to visualise it from the larger-coverage (optical limit) image (which frankly my imagination/visual capabilities are not up to).

A very interesting difference between shooting raw natively (which disables digital zoom) and shooting it with CHDK (which doesn't). I am certain to try this with CHDK in the SX50. I never thought to use CHDK that way with my SX20 which I shot almost exclusively with raw after CHDK came out for it.

Also, when going for an image beyond the optical limit, and working hand-held (sometimes one-handed for shots at awkward angles) as I do with the SX240, there is a lot of movement of the image on the LCD. I can't hand-hold steadily enough to keep the framing exactly where I want it. However, when I am in digital zoom territory it doesn't matter if I slightly cut off one side or another in various attempts at the shot, because there is "slack" available around the edges that I can make use of when doing the crop later.

Another good comment and idea!

Doing the crop later has another advantage. I have the JPEG to remind me what I had in mind when I took the shot, but more than once I have discovered, when looking at the RAW version with its wider coverage, that there is a crop that I like better which uses more of the RAW image than what I saw on the LCD at shooting time. Of course if I had actually used the digital zoom JPEG as the source of my image I wouldn't be able to do that.

And there is a big benefit in handling noise. I tend to use rather high ISOs, but details and textures matter a lot to me. The higher ISO JPEGs have lots of detail/texture smudged away irretrievably by the in-camera noise reduction (and there is no option on the SX240 for turning the noise reduction down). Processing a RAW version means I get to decide what compromise to make between noise reduction and detail retention, suitable for the size of the output medium and my own preferences as to the "look" of my images. I can also use more subtle, image-specific approaches to noise reduction than the camera, for example applying different levels of noise reduction to the subject and the background, and/or to different parts of the subject and/or different parts of the background.

That's basically why I used CHDK almost exclusively for raw with my SX20.

RAW also gives benefits in terms of retaining details in highlight areas/recovering areas that are blown in JPEG versions despite my habitual under-exposure to try to avoid it.

All in all I'm sure this is the best way for me to work, but I have to say in the couple of days after I got the camera and before I started using RAW, I had been pleasantly surprised at the image quality that the camera could produce up to 2x or perhaps slightly more digital zoom (ie actual, camera-produced JPEG digital zoom rather than "DIY digital zoom"/cropping from RAW that I've been talking about here).

Thanks for your thoughtful comments and analysis.


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