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-   -   Megapixels Compensating for Optical Zoom: Good Idea???? (

PaulyEddyFreddy Dec 22, 2005 8:25 PM

Hello, I have a super Canon SD230 with 3.2mp and 3X optical. I am thinking of upgrading to possibly a Canon SD550 with 7.1mp and 3X optical. Question is if I take say, a group shot with the SD550 and then with my picture software create just a head shot of one person in the group, will it be of the same quality as my SD230 headshot picture from an uncroppednormal distance. Logically, this would be true, but... taking pictures by hand can do lots of movement at a distance, so I don't know. Is it worth getting a more-mp camera mainly for the sake of creating an artificial larger optical zoom (like using the super useless digital zoom). Hope some of you have done this and can help me. Thanks ahead of time.

tennisforums Dec 22, 2005 8:41 PM

If you are going for a 3mp camera, but are looking for a larger optical zoom for around the same price, I would go for the Panasonic Lumix FZ3. It has a 3.3 mp sensor and an incredible 12x optical zoom- you won't need to do any cropping.

Only thing is, I'm not too sure about the image quality. Many people swear by this line (FZ3, FZ4, FZ5), but I have read a few comments about the noise levels. I would personally go for zoom over megapixels. 5.0mp is really all you'd need, most people can't really tell any difference between 3.0mp and 6.0mp at 6x4 sized prints.

PaulyEddyFreddy Dec 22, 2005 10:00 PM

Thanks TF, but my question is really related to cropping than the specfic cameras (although I have been researching 7mp pocket cameras). SayI take a head shot with a 3mp camera and then take the same shot from farther away with a 7mp camera. If I then crop the 7mp shot to get the picture to be effectively the same as the3mp picture, will the quality be the same. What I am trying to find out is can I use a 7mp small pocket camera to take 3mp quality pictures by using cropping as an additional zoom beyond the standard 3X optical----and still get quality shots tha same as the 3mp camera up close. Hope I haven't confused things even more. :-)

P.S. Independent of your answers, if you have other recomendations for a good 7mp small pocket camera, let me know. I don't use much manual stuff, just a bit.

Thanks again.

tennisforums Dec 22, 2005 10:17 PM

Well, that is a difficult question. I would have to say that the 3mp photo would still look better, because it could be proportioned down to the same size as the cropped 7mp photo and would therefore look better. Whereas if you cropped the 7mp photo down to the size of the 3mp photo, you would be working at full size, depleting the quality further.

Also, higher megapixels also tend to have higher noise at full size.

tennisforums Dec 22, 2005 10:24 PM

In regards to your latter question, I would have to recommend the Canon Ixus 750. It has a 7.1MP censor, 2.5" screen and is one of the fastest high end compacts available.

As a generalised statement, Cybershots usually deliver top quality due to their Carl Zeiss lenses, however, they can be a tad overpriced. The Sony Cybershot DSC-P150 is an exceptional camera with 7.2MP photos. It is also ultra-slim and compact.

Both only have 3X optical zoom lenses, but if you don't really prioritize the zoom, then they should both be excellent cameras.

JimC Dec 22, 2005 10:35 PM

The short answer to your question is No (cropping is not a substitute for optical zoom, all things being equal, and you're not going to make up for it by going from 3 to 7 megapixels and cropping).

If you crop a photo to make it look like you used twice as much optical zoom, you'd end up with only 1/4 the original resolution.

See my reply in this thread

airshowfan Dec 23, 2005 12:04 AM

I agree with JimC.

Sure, if you crop a high-megapixel image, then the crop will have fewer pixels (be a smaller area), but if you started out with a lot of megapixels to begin with, then the crop might still be quite high-resolution. However:

1) Cropping by a certain factor will reduce the area, and thus the pixel count, by the square of that factor. So cropping an 8MP image and taking the middle half (if you imagine a grid of 16 rectangles, 4x4, then I'm talking about cutting out the "edge" 12 rectangles and keeping the middle 4) will leave you with a two-megapixel image. This is why a few more "X" of optical zoom usually gives much better image quality than cropping by that amount, even in a high-megapixel camera.

(The pixel number in the cropped area goes down real fast as you crop in. For example, take a 5-megapixel camera with 6X zoom. For another camera, one with 3X zoom, to produce images that could be cropped to look like 6X zoom images and still have 5 megapixels, then that other camera would need to have 20 megapixels).

2) When you crop, the grain/noise becomes more evident. Since the pixel density of higher-megapixel cameras tends to be higher, this grain tends to be worse, so a two-megapixel crop from a five-megapixel image will usually look a lot worse (more noisy/grainy) than an image taken with a camera that has a maximum resolution of two megapixels. This is especially true in compact cameras. So even if you COULD crop and keep a high resolution, it would look worse than having that resolution as your camera's maxiomum. You can see this demonstrated (with examples) at

So get something with good optical zoom so that you don't have to crop significantly, if you can avoid it.

(And of course I crop most of the shots that I like, in order to adjust the composition a bit and so on. But I never crop out more than 1/4 of each edge, which means the area never goes below 50% of the original area. Even that looks pretty bad - I try to not crop out any more than 10% of each edge if I can help it at all).

Carskick Dec 23, 2005 12:16 AM

The only way I could see this happening is if the sensor got significantly larger. For example, if you had your 3MP had a 1/2.5inch sensor, you'd have to go up almost to a 1 inch sensor to maintain enough detail per pixel to make up for optical zoom. The 1/1.8" sensor in the SD550 is not going to have as much detail per pixels as a 3MP camera with 1/2.5". Even if the area of the sensor did increace that much, the lens would also have to capture more detail to maintain quality cropped.

KENNETHD Dec 23, 2005 4:48 PM

Bottom line? Your zoomed in shot should be the best. As you can readily see from other posts, cropping cuts the pixel ratio incredibly. Strictly going by pixel count, you will have a more saturated and sharper image just zooming in and not having to crop. Of course, we're talking about a group photo vs a head and shoulders of someone in the group so you'd be cutting away an enormous amount of the original pixel real estate. Hands down, the zoomed in should be by far the better pic. Best regards,


PaulyEddyFreddy Dec 23, 2005 5:04 PM

Wow!!! You guys are super!!! I thought I might get a yes/no type answer. All your opinions had good sound technical reasons. That really helps me. I am definitely going to reconsider the "need" for a more-mp camera. Thanks again and Happy Holidays to all of you.

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