EX zoom, i.zoom and digital zoom

Started 2 months ago | Discussions thread
Dak on cam
Dak on cam Senior Member • Posts: 1,329
Re: EX zoom, i.zoom and digital zoom

dbelling wrote:

kkardster wrote:

dbelling wrote:

I realize that this topic has been raised before, but I found this Graham Houghton video on the subject to be of interest:


If I understand him correctly, he is saying that i.zoom is superior to EX zoom and that both are better than regular digital zoom (which is probably right). But it surprised me that he believes that i.zoom is superior to EX zoom. I would have thought it would be the other way around.

I believe this is only true for 1" and larger sensor models. For smaller-sensored models i.Zoom doesn't offer much.

That could be because Graham produced a video some time ago about the FZ200 (smaller sensor) in which he stated exactly the opposite. That is, EX zoom is preferable to i.zoom.

I've taken a look at the video right now, and Graham is wrong about a few things, and ambiguous about a few others.

Where he is wrong is that digital zoom or cropping does not make a difference with regard to bokeh/DoF.  If it didn't, there'd not be a point in giving 2× magnification when manual focusing.  Depth of field is determined by what amount of unsharpness you can still see, and at larger magnification, more unsharpness becomes apparent: the size of the "circle of confusion" shrinks.  While the entrance pupil stays the same size and the relative size of bokeh compared to object size also stays the same, it is the absolute size of the bokeh that determines depth of field.

Then he talks about digital zoom providing more pixels for making prints.  That makes a difference only when the printing device is more stupid about upscaling than the camera is.  A PostScript printer or similar might be in that ballpark, a photo printer should not.  The problem is that you really should hit the proper resolution of the print device in otder to get best results, and the camera doesn't know what that resolution would be.  The print device does.

He makes his comparisons then by downscaling to video where of course any difference is then compounded again.  He also states that you'll get noise reduction by integrating pixels in extended zoom.  This is somewhat correct but you get most noise reduction by integrating the covered areas which is not the best strategy with regard to avoiding Moiré patterns.  Also of course it makes no difference if you afterwards reduce the resolution to less than you started with.

He does point out that working from raw will always give equivalent results, but that i.Zoom et al give you better tools for framing and image quality if you are going to work with a crop from the original sensor anyway.

But with my FZ200, I actually can enable i.Zoom and raw, and the camera will just record the raw crop of the sensor corresponding the i.Zoom framing.  Indeed, at full iZoom and full JPEG quality, the raw file ends up smaller than the JPEG.

Now in comparison on my DSC-R1 with its mechanically linked zoom, I have a button that can either do the equivalent of extended zoom or digital zoom.  That would be great for a quick quality check on the small-resolution LCD screen or viewfinder, but alas, the button refuses to work unless I am at JPEG only and raw is only available at the full 10MP pixels.  Way to ruin a prospective good feature.

 Dak on cam's gear list:Dak on cam's gear list
Sony Cyber-shot DSC-P52 Sony Cyber-shot DSC-H1 Sony Cyber-shot DSC-H2 Sony Cyber-shot DSC-R1 Panasonic Lumix DMC-FZ200
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