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Old Nov 7, 2005, 7:59 PM   #1
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Hello,

Can someone tell me the difference between a 5 megapixel vs a 7 megapixel camera if everything else is basically the same?

Example the Canon A610 vs the A620.

Is there any difference in the size print that can be made with each camera (and what size can they do)?
Is there any difference in the quality of the image?

Thank you,
Juggernaut
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Old Nov 7, 2005, 8:48 PM   #2
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er... 2 megapixels.

Yes, you could make a slightly larger print from the 7MP, before having to resize the image, or you could crop a little more. But basically there is not much difference between the 5MP and 7MP cameras (all else being equal). Especially if you never print anything larger than 8x10.

If the CCD size is the same, the 5MP might actually perform better. A tad less noise, a tad more dynamic range and a tad more high ISO performance.

But from a practical standpoint, probably not noticable. Now if the 7MP CCD was larger than the 5, then the scales might tip in favor of the 7.

All in all, nothing really to worry about, and the 5MP is probably cheaper.

Declan
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Old Nov 7, 2005, 10:19 PM   #3
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I agree.....

I had a chance to get either an 8mp Minolta-A2 or a 5mp-A1, so I got the A1. Mainly because the sensors are the same size & the A1 produces better images at higher ISO's than the A2 can (due to the sensor having fewer photosites, resulting in cleaner images).

As an example...the A2 had it's lowest ISO at 64 & made great images at that setting. The A1's lowest ISO is 100 & it makes great images at that setting. The A1 also makes great images at ISO 200, but the A2 has much more "noise" at ISO 200.
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Old Nov 8, 2005, 1:17 AM   #4
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What would you rather have? An 8mp with the lens like the bottom of a beer bottle or a 5mp with a first class lens. Ok, all things being equal the 8mp will give you a slightly larger shot . The choice is yours.
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Old Nov 8, 2005, 8:52 AM   #5
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All else equal (it never is), you can make a print 18.32% larger (square root of the pixel count ratio). Nice to have, but it is easy for other differences to be larger. Things like noise/high ISO, lens quality, lag time, feel in your hands, viewfinder/EVF quality, features, price,...
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Old Nov 8, 2005, 10:20 AM   #6
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As far as resolution goes, there's about a15% difference between the two. As far as print size goes, you could get a 10.23" x 7.68" print from 7.1MP or a 8.64" x 6.48" print from 5MP.

This is not saying that is the largest you could get, just what you get that you could view from a few feet or from a few inches and have your eye see the same amount of detail.

Megapixel count mainly affects largest print size and amount of cropping that can be done as previously stated.

The A620 and A610 are definately the best A series camera's Canon has made and both produce pleasing 8" x 10"s. I personally wouldn't spend the extra $100 for that slight a difference in resolution.
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Old Nov 8, 2005, 12:50 PM   #7
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As a general rule the compromises mentioned are true. In the specific case of the Canon A610 vs the A620 you get a free ride. Assuming those are Sony sensors, the 7Mp 1/1.8 sensor is of sufficiently improved technology that you don't take a noise hit going from 5 to 7Mp. The optics are the same, so you just pay a little more and get some more pixels.

The 7Mp gives you very roughly 30% more pixels. That means you can make a print 30% larger in area at the same resolution or make a print the same size with a 30% higher pixel density. Or you can crop 30% from the image and still have 5Mp. Someone once pointed out that I calculate the increase wrong. Since you start with 5Mp and add 2Mp more, you could consider it a 40% increase since 2 is 40% of 5.

I have a wide format photo printer and like large prints for the wall. There is a definite quality improvement in a 13 X 17 print going from 5 to 7Mp. The best print I can get from a 5Mp image is around 148 PPI without removing anything but the part I need to get the right ratio. That doesn't make a bad print, but the extra 2Mp improves it noticeably.

If you frame the image perfectly you can get a 240 PPI 8 X 10 print from a 5Mp camera. I don't see any improvement over 240 PPI with either of my photo printers. If you frame the image perfectly in the optical viewfinder you will have about 20% to crop off because the optical finder shows only about 80% of the image. I almost always have to crop a little if I use an optical finder. That crop will take you to around 190 PPI, which is still very good. Many people print 8.5 X 11 as most photo paper comes in that size and there are plenty of frames available in that size now. With a 20% crop you are down to around 175PPI. You can see an improvement going above 175 PPI, but not much.

If you frame with the LCD and don't have to crop, you get an 11 X 14 of around 175 PPI. That makes a nice print.

You can upsample any image, but it doesn't improve the resolution. If the resolution is low enough that the pixels are showing an upsample can make it a little smoother, but there isn't any magic upsample system that will give you more resolution than the raw pixels. That isn't to say you can't improve an image in post processing.

The extra pixels give your more latitude to crop the image. I seldom take a picture that doesn't look better with a little cropping, especially using the optical finder on a small camera.

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Old Nov 8, 2005, 1:54 PM   #8
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Good reading here. Bottom line? Go for the extra 2 MP. Why? Sooner than later you will shoot a shot that you wish you were a bit closer, or you'll want to crop for a cleaner image. The extra MP real estate will make a noticable (but not earth shaking) difference. In the end it will increase your number of keepers by a good margin. (IMO)

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Old Nov 25, 2005, 2:40 PM   #9
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A well-reasoned explanation about cropping and print resolution, slipe. My sentiments exactly, except I tend to keep as close to 300ppi as I can for images I want to print --- certainly no lower than 270ppi if I need to get an 8 x 10-inch print from a 7Mp image. The point about having more latitude for cropping when you've got more pixels is very true, as long as you realise that for a compact with a small sensor, I would say 7Mp is probably as high as you should go --- if you want any more than that you need to be looking at cameras with a larger sensor to accomodate the extra pixels without them being ridiculously small. Oh, and on the subject of cropping, one guy on another forum told me you never need to crop if you're any good at taking pictures, it should be okay just as it is! I was tempted to start a flame-war, but then decided to rise above it and if that's what he thinks, big deal.
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