Quality vs camera resolution

[gjugger]

I would appreciate knowing about relative image quality on two cameras - a 5mg vs. a 7mg when the 5mg is taken at its maximum resolution of 2592x1944 and the 7mg. camera is at a reduced resoluton of the same quantity. In other words, is the higher resolution camera giving up some of its quality when it is reduced below its maximum resolution? Please help. Thanks,

[haikai]

i had never thought about this because i always shoot at the highest resolution... it's an interesting question. if i were to hazard a guess, i'd say the camera takes the image at the highest resolution and will down-res the image to whatever you had selected. provided the image processing was decent there really shouldn't be any problems with this. or so i'd like to think... anyone know for sure? :o

-hai

[speaklightly]

gjugger-

It is just my personal opinion, but I believe that there are more things than just resolution that affect image quality. The camera's lens plays a large role, as does exposure and the ISO used. Finally we cannot dicount electronic noise. I feel there are more factors at play in this equation than just resolution.

Sarah Joyce

[gary_hendricks]

Totally agree with Sarah on this one. The number of megapixels is never the only thing you should consider when buying a camera. It's a marketing trick.

Read this article to understand how many megapixels you really need in a camera (http://www.basic-digital-photography.com/how-many-megapixels-do-you-need.html).

[jeff31]

I think that more resolution contributes to the resolving power. With more resolution you could see theoricaly more details. An another criterion participes to have a good image: the size of the CCD sensor. It is not a surprise that in some conditions a 5MP 1/8" provides a better images that a 7MP 1/8".

[gary_hendricks]

I think that more resolution contributes to the resolving power. With more resolution you could see theoricaly more details. An another criterion participes to have a good image: the size of the CCD sensor. It is not a surprise that in some conditions a 5MP 1/8" provides a better images that a 7MP 1/8".

Agree, but I guess the number of megapixels is a determining factor if you want to make large prints. For normal viewing (e.g. on the TV or computer), it doesn't make so much of a difference.

[speaklightly]

Am I correct in concluding that many more factors, other than resolution, affect photo quality and clarity?

Sarah Joyce

[D70FAN]

I think that more resolution contributes to the resolving power. With more resolution you could see theoricaly more details. An another criterion participes to have a good image: the size of the CCD sensor. It is not a surprise that in some conditions a 5MP 1/8" provides a better images that a 7MP 1/8".

I think you mean 1/1.8 which is a 0.55" sensor. ;)

[D70FAN]

I would appreciate knowing about relative image quality on two cameras - a 5mg vs. a 7mg when the 5mg is taken at its maximum resolution of 2592x1944 and the 7mg. camera is at a reduced resoluton of the same quantity. In other words, is the higher resolution camera giving up some of its quality when it is reduced below its maximum resolution? Please help. Thanks,

I think you mean 5MP (megapixels) not 5mg (milligrams). ;)

[Balrog]

Interesting question .. for argument's sake, assume we had two identical cameras, except one had an 8MP sensor and the other, 2MP. The question as I understand it is how would the quality compare if you used either camera to take pictures at 2MP resolution .. There are two things the 8MP camera could do - either 1) it takes the shot with the full sensor (8MP) and downsamples it to 2MP, or 2) it simply crops the central 2MP of the sensor output .. except, hmmm .. the second case would essentially result in a 'digital zoom' of 2x .. so the output wouldn't be identical.
I guess it'd have to downsample then, in which case the quality would be dependent on the algorithm used - some kind of antialiasing would have to be applied. I'd hazard a guess that the downsampled 8MP image might possibly contain somewhat less noise than the direct 2MP image of the other camera, but you'd have to test it out to be sure... other than that, 'image quality' would probably be about on par.

[rucyj]

The general point about offering different resolutions in any camera is to allow a compromise between absolute quality and size of file.

A 2 or 10 mp camera will still take pictures at that size, but will sample (or compress) the result according to a software algorithm to make the file size fit given parameters, as defined by the camera maker.

The quality of the result has a great deal to do with the programming algorithms used to decide what picture information to discard. Camera reviews will often comment that the result is 'blocky' even for a high mb camera where the code is not good enough.

Try re-saving a jpeg image a few times and see what happens. The size reduces, as does the quality. However, the quality is not an issue until you need to do something with the result, such as blow it up in size, or print it out. Even a lower resolution result from a camera will be good enough if all you want to do is view it on the screen or print out 6*4 snaps.

Effectively the best quality will be uncompressed images storing all the data captured by the chip. This would preferably be TIFF or equivalent. The maximum sensible size would then be a function of pixels captured vs print or display device resolution.

Cropping is sort of compression in reverse. Instead of reducing a file size to suit a storage requirement, the crop selects a smaller image; but you are trying to make it fit a larger viewing size, so effectively blowing it up beyond its capabilities.

It's an interesting topic with many detailed technical arguments. What has also already been said is true, that the quality of the lens and chip and other mechanical factors will also affect the result regardless of large mp values(see other discussions about noise in dark pictures, for example).

[gary_hendricks]

There are a ton of arguments we could go on and on about image quality versus megapixels. Ultimately, it is a combination of factors, light, megapixels, environment, EXIF settings that determine if a picture is of good quality.

[gjugger]

Thanks for the comments, especially for Balrog's. I had a specific purpose for raising this question. I am seriously considering the purchase of either the Canon SD-400 (5 mp) or the SD-500 (7mp). For most of my uses, the 5mp is more than adequate, but I like many of the features of the 7mp better. Should I purchase the 7mp I would use it most of the time at the lower resolution of 5mp or less. I didn't want to lower the quality level of my pictures by using the 7mp camera at the lower resolution. Comments in this regard would be appreciated.

[haikai]

as jeff31 pointed out, an argument can be made that the higher megapixel camera can theoretically achieve more detail if shot at the same size as the lower res camera (assuming that what the camera does is indeed take the image at the highest res it can and then down-res).

the difference between 5 and 7 mp, in this case, is probably negligable, but let's say you had two 1000 pixel images- one taken at 1000 pixels to begin with and another taken at 10,000 pixels and then shrunken to 1000 pixels. the 10,000 pixel image will have undoubtely captured more details... when the image is downsized, whatever algorithms go on under the hood should retain these extra details as much as possible (even if all it does is reduce them to subtlely colored pixels) whereas the untouched 1000 pixel image never had enough room for those details in the first place so it was never captured.

this is what tends to happen in 3d computer graphics (not to get too off topic). when rendering 3d stills, it is recommended by some to render at about twice your target size and then downsize the image to ensure the most visual fidelity possible. otherwise, the computer will generalize certain details and the aliasing will be too broad (especially on very thin and long line details like ropes/cables). i'd like to think that a similar thing is happening in the digital camera world, but anyone please correct me if i'm wrong!

of course, as everyone else has been saying, a 7 mp cam does not necessarily take better quality images than a 5 mp image as far as color, noise, lens distortions and all that, but it should give you that extra bit of resolution that could potentially contain more details... however, it may be unlikely anyone would notice these extra details on a regular sized print anyway :p

well, good luck with whatever you end up going with!

-hai

[gary_hendricks]

HI,
Sure High resolution Plays vital role in image Quality.But other factors are also concerned.And in some cases they aer more importand.LIke ISO rating.ISO raing of ur camera is high than it is high sensibal to light and can take good pictures in less light or darker environment.Another is White balace which is related to different light levels.Flash also plays major role in low light.

ALso CCD is good for image sensor.But now a days CMOS is also getting more compititive.

So look all the parts not only the REsolution is imprtand others are 2. :eek:
Bye,
:)

[Geoff Chandler]

Oh my Goodness - what a HUGE Jar of Worms this one is!!!
I have experimented with all this a bit and there are no totally definitive conclusions to be drawn!! - however there are some helpfull pointers.
My 8mp cmaera resolves better at 3mp than my 3mp camera - now I can't tell you for certain why this is (read some of the previous comments) I believe however that a few extra mp available is no bad thing, and I don't use my cameras at top resolution all the time. A close up of a fairly large object shouldn't need super high resolution as you won't be blowing up a small portion for closer scrutiny - therefor it would be a waste of storage space (IMO). However - I have found a great benefit when photographing highly fine detailed scenes in using the extra resolution. Sometimes a slightly lower mp setting can result in an apparently sharper image - I have also found this when scanning - at normal veiw size the image of a slightly smaller sized picture appears sharper and therefore more pleasing - only when you greatly magnify the two pictures do you discover the additional detail. So now I find myself thinking what will I do with this photo when I take it, and then deciding what size to take it at. A series of close up people shots taken with the telephoto end of the lens was absolutely fine at 3mp ~ didn't need any more than that. Sure it might be better to take them all large and downsize afterwards - if you have the luxury of enough storage space - during my holiday I was aware that I had a limit in storage space and no handy downloading facility, so I didn't take all my pictures at 8mp - in fact even with the detailed scenes - the difference between 8mp and 5mp was quite small - and would only show up on a big crop and large print.
Finally, whilst I don't really like compression - I have to say that a small bit of compression is not very visible and that a larger image compressed a bit seems to render more fine detail than a smaller image not compressed - just what I have found - not neccesarily the final word on the subject.

[richwolf]

Isn't the quality of the lens very important too plus it's ability to take in more light?
It seems lens quality is often overlooked when it comes to picture quality. With film it always seemed to be about the lens and film quality.
Who cares if you have a jillion megapixels if the lens is of poor quality?

[D70FAN]

Isn't the quality of the lens very important too plus it's ability to take in more light?
It seems lens quality is often overlooked when it comes to picture quality. With film it always seemed to be about the lens and film quality.
Who cares if you have a jillion megapixels if the lens is of poor quality?

Always one of my favorite examples: This picture was taken with a dSLR. Can you guess which one? (thanks to Cold Snail):

[Geoff Chandler]

Isn't the quality of the lens very important too plus it's ability to take in more light?
It seems lens quality is often overlooked when it comes to picture quality. With film it always seemed to be about the lens and film quality.
Who cares if you have a jillion megapixels if the lens is of poor quality?
I couldn't agree more! (- I think I felt I had already written toooo much without starting on about lenses as well) - as the old saying goes (& one I liked in the world of HiFi) Rubbish in = Rubbish out. Use a naff lens with a high mp and you get a high resolution blurred pic!! But best to take a centre road as a brilliant lens with hardly any pixals would also be undesirable - though I don't think any such beast would exist now.
George's pic is a perfect example of a great lens on a reletively low mp camera - it looks great doesn't it.

[D70FAN]

I couldn't agree more! (- I think I felt I had already written toooo much without starting on about lenses as well) - as the old saying goes (& one I liked in the world of HiFi) Rubbish in = Rubbish out. Use a naff lens with a high mp and you get a high resolution blurred pic!! But best to take a centre road as a brilliant lens with hardly any pixals would also be undesirable - though I don't think any such beast would exist now.
George's pic is a perfect example of a great lens on a reletively low mp camera - it looks great doesn't it.

Actually this is a 1.3MP Kodak DSC410 (or 420). Circa 1994!!!

http://www.mir.com.my/rb/photography/companies/Kodak/index1.htm

I think Cold Snail converted it back to an N90 film camera.

[Geoff Chandler]

Actually this is a 1.3MP Kodak DSC410 (or 420). Circa 1994!!!

http://www.mir.com.my/rb/photography/companies/Kodak/index1.htm

I think Cold Snail converted it back to an N90 film camera.
Well - it just goes to show the one thing everyone has forgoten to mention in this is how good the photographer is!!!

[D70FAN]

Well - it just goes to show the one thing everyone has forgoten to mention in this is how good the photographer is!!!

This is one of those pictures where the more you look at it the more personality of the squirel grows on you.

Kudos to Cold Snail.