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scar_ace Jul 9, 2004 3:25 PM

When I use precision zoom I can tell on the LCD that it has a more computer generated effect, but why?
I will most likely always be on 5MP on my W1 so it wouldn't change much, just curious as to why they differ.

Thanks all

JimC Jul 9, 2004 6:24 PM

I would strongly advise you to avoid BOTH types of Digital Zoom.

Sony's "Precision" Digital Zoom is cropping and interpolating the photo. Basically, this is taking the image (5 Megapixels), keeping just the center portion of what is being captured by the CCD, then discarding the borders. This makes it appear that more zoom was used (when in fact, it was not).

It then interpolates the image, back up to the full size again. Basically, this technique fills in the missing pixels, by looking at the values of adjacent pixels.

For example:

If you use a 2X Digital Zoom without any interpolation, you'd endup with an image that's only about 1/4 the Original Resolution (not much over 1 Megapixel). This is because resolution is computed by multplying width times height.

Then, the interplation used, enlarges the image back up to the full size you were shooting at (i.e, 5 Megapixels), filling in the image with additional pixels (that were never captured by the sensor).

"Smart Zoom" is different. It's only available when shooting at resolutions below what the sensor can capture. So, it is only cropping the image (keeping the center portion, then discarding the borders). It looks better on screen, because it's not trying to fill it back in with pixels that were never captured to begin with. Of course, you end up with alower resolution image than the sensor is capable of capturing this way.

Basically, I'd advise not using Digital Zoom of any type. You can do a better job later using software. Cropping a photo is simple, and virtually any image editor can do it. As far as interpolation (if you need to make the smaller image larger for print purposes), you can find excellent software for that also. Even the totally free Irfanview (downloadable from ), has pretty decent interpolation algorithms available.

Personally, I think that manufacturers should have a big warning label on their products "Warning - Digital Zoom will either 1. Degrade Image Quality because of cropping and interpolation; 2. Give you lower resolution Images, which will degrade print quality"

scar_ace Jul 9, 2004 7:28 PM

Thanks Jim, I understood that perfectly (interpolation, from my dreaded statistics modules). It's a bit misleading of Sony because although they sort of mentioned Precision zoom would degrade quality, they didn't mention anything as such about Smart zoom.

Thanks again

Pipkin Jul 9, 2004 8:15 PM

Here is additional infoof digital zoom. Maybe it would be useful, though JimC talked entirely about.

scar_ace Jul 9, 2004 8:49 PM

Hey thanks for that Pipkin as well

Cybershot455 Jul 10, 2004 4:02 AM


(Hello Jim, you'll be amazed after all our forum chats many weeks ago I'm still really enjoying using my P10!)

I think it is a bit hard to sayavoid using the Sony Smart Zoom. "If" you are using a resolution less than the maximum then the availability of an extra zoom range beyond the usual 3x *with no loss of quality* is actually a positive feature. The SamrtZoom does just this.

PersonallyI hardly use it, post capture cropping on the PC is my favoured method. However there are "point & shooters" who do not delve into PC image editing that would like this facility.

An actual example is my Uncle who bought an overlarge camera to get a 6x zoom but never takes images above 1.3MP (web and mail use). By the time he has his camera in a padded case he might as well be lumping about an SLR....and the only thing this bulky camera does over many others is double the zoom range.

Well he could have my compact 5MP Sony, set it to 1.3MP and let the SmartZoom take him right up to an effective6x zoom with no quality loss. Overall it might be a better solution for him but not one that a conventional digital zoom could achieve.

Also your "Warning - Digital Zoom will either 1. Degrade Image Quality because of cropping and interpolation; 2. Give you lower resolution Images, which will degrade print quality" is a bit unfair. SmartZoom doesn't give you lower resolution images that degrade print merely works at lower important difference.


Your links were interesting, the one to particularly so. I'd be interested if some of you looked at it and read the bit of the V1 review where the guy has presented a case that the 3.1MP setting on the V1 gives 98% of the image quality of the 5MP setting. It seems very plausible...what do you think?

Last year we bought back 200 images from our holiday, all at 1.3MP on our 3MP camera. At 6x4 prints from the Sony online lab the results were excellent. Now I have a 5MP camera I'd thought of going for max res images this time but need more memory sticks, reducing to 3.1MP would help a great deal.


Sinister Purpose Jul 10, 2004 9:32 AM

Theproblem withthe Smart Zoom is that the optical viewfinder does not show the extra zoom– you need to use the LCD. This is fine if you are aware of thisand can see the screen under the lighting conditions. Otherwise, if you are using the optical viewfinder,you may be inadvertently cropping unintended parts of your image. That might not be good!

JimC Jul 10, 2004 2:10 PM

Cybershot455 wrote:

SmartZoom doesn't give you lower resolution images that degrade print merely works at lower important difference.
But, lower resolutionmeans lower quality when printing, and "newbies" maynot know this (that they need a certain number of pixels perinch, for the image size they plan on printing). They are looking at those nice stickers on the camera boxes and cameras, which usually have big bold numbers with the amount of total zoom (Optical + Digital), followed by the numbers from both (not as large, of course).

These stickers also don't tell you anything about Digital Zoom degrading Quality, much less try to distinquish the difference between "Precision Digital Zoom", and "Smart Zoom".

Heck, I see far too many "which camera should I buy" queries on forums, giving Optical and Digital Zoom numbers, believing that the model with4x Digital Zoom, is better (from a Focal Range perspective), than the model witha 2x Digital Zoom (given the same Optical Zoom Numbers).

Ifthey realized how it works, then they'd probably look at models with greater optical zoom instead (if they need the extra magnification for the type of shooting they are planning on).

It's on my "Pet Peeves"here (see the section on Digital Zoom):;forum_id=2

Anyway, to be fair, there are a couple of legimate arguments for using it, and some people (even knowing how it works) still use it for some applications. Personally, I keep it disabled on my cameras (so I never accidently use it).

I'm glad you like you're enjoying your P10.

Cybershot455 Jul 10, 2004 3:24 PM


I'm know I'm a bit of a pain sticking up for Sony so much but I'm really trying to get across the point that even if there is nothing to gain with SmartZoom, there is never anything to lose.

There is no reason to turn off SmartZoom because it will only work when it is able to do so without losing quality. It is not the operation of the SmartZoom that will reduce the quality in the situation you mentionbut the delving into the resolution menu and taking the choice to reduce resolution. This, as I mentioned above, can be done for many legitimateapplications and still maintain perfect results.

You have to establish a line between a normal digital zoom and SmartZoom to be fair to the designers who tried to move things on a stagefor our benefit.

Anyway forget all that, what do you reckon to that link Pipkin mentioned, and the one I highlighted, where the chap makes a case for a 3.2MP image having 98% of the quality of a 5MP image??

I'd value your thoughts on it.


Witek Nov 30, 2005 7:38 PM

What other cameras (except from Sony) have some sort of SmartZoom? And I mean SmartZoom, that is using the full sensor resolution and cropping down the image to the user set (lower) resolution and not interpolating the image.
I wish Canon PowerShot S80 had it. If so, I'd buy it.

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