Digital zoom problem - General Discussion and Assistance - CHDK Forum

Digital zoom problem

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Digital zoom problem
« on: 28 / July / 2009, 17:21:07 »
Hey all, and thanks in advance if you even read this :)

The problem i have, goes like this:

When i take a picture using optical zoom, everything is fine. Converted DNG, jpeg and everything is hunky dory, but... When im using digital zoom, the zoom isnt occuring on my converted DNGs. So, in other words i see the zoomed picture on my jpeg, but DNG is just.. like there is no zoom at all.

So, is that a problem in my chdk settings, my DNG converter or what the hell is going on there? :)

Oh, im using Powershot SX100 IS, but i think thats irrelevant on this one...

Thanks in advance,


Re: Digital zoom problem
« Reply #1 on: 28 / July / 2009, 21:06:17 »
Nothing wrong with camera or CHDK!..

Digital zoom just enlarges the central smaller area of the image (sensor) after the lens zooms to its maximum optical zoom and then the camera processor converts the same to JPEG. Therefore you cannot obtain an enlarged RAW. This is true for all cameras.
You can obtain the same or better quality of image without using digital zoom by simply enlarging, processing and converting the central area of your RAW image to JPEG's.

Re: Digital zoom problem + long exposure shots
« Reply #2 on: 29 / July / 2009, 04:57:31 »
Thanks a lot for a fast reply, i was thinking its something like that, but hey... 2 brains are smarter then one (in most cases ;))

Anyways, not to opening new topic, i'll ask here (was searching through forums, but couldnt find any suitable answer).

Im doing some long exposures shots, and its all perfect until i try to do em on a daylight/ sun basis (as you'd imagine). All i see then is, as you would've guess - whiteness.

So, to sum it up, is it possible to somehow pull it off via script or some overriding camera default settings?


Offline nonno

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Re: Digital zoom problem
« Reply #3 on: 29 / July / 2009, 05:47:33 »
you can only try to override the ISO value to use the lowest possible value and override the aperture to close as much as you can you diaphragm. But your images will be still totally overexposed in a sunny day, no way to do it with CHDK.
I think you should use something like a (heavy) ND filter, depending on how long you want to expose. Just check (you can also use CHDK miscellaneous values) the Exposure value of your scene and you will know all the couples time-aperture you can use to expose it right. If you know the time you want you will easily know the aperture you need. But i think that the aperture you'll need in a sunny day will likely be impossible to obtain, so you have to reduce the light that enters your lens with ND filters (or maybe at least with a polarizer but i don't think it is enough).


Offline fudgey

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Re: Digital zoom problem
« Reply #4 on: 30 / July / 2009, 15:37:50 »
If minimizing ISO and aperture isn't enough and an external ND filter is out of the question, you can always try blending (on a PC) multiple exposures taken in a row. Obviously this is not good for all applications of long exposures, but could suit your purposes, whatever they may be.


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