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why are more pixels not necessarily better ?
If I want make poster size printsI would think that I would need as many pixels as possible ? I know that sensor size plays into it also. Somepeople say don't go over 6 MP'sWhy is this? I am thinking of getting a G9 (12+ mp's). All I want to do is take pictures of the streams where I Fly Fish , to help keep the memories alive ! So I guess the question is " would this be the right carmera for me ?" thanks steve..

Comments (10)

I believe there are two basic reasons why more pixels are not necessarily better..

First is that there's a lower limit to pixel spacing called the diffraction limit, about 2-3 microns for a normal lens..

Second is that as pixels get smaller in area they get noisier; to be precise the signal to noise ratio decreases at least as fast as the diameter of a pixel..

The above comments don't mean it is bad to have a lot of pixels; just that they shouldn't be too small. Most cameras increase pixel count by decreasing pixel size..

In fact, the more 5-6 micron pixels you can have the better. If you can afford it, get a digital Hasselblad..

When printing your picture as a poster it is often helpful to artificially increase the pixel count by interpolation to avoid unsightly pixelation. The following clown's nose shows what I mean - doubling the pixel count in each direction on the photo added no information, but made the image smoother..

Image control:Zoom outZoom 100%Zoom inExpand AllOpen in new window..

Comment #1

Do you know the pixel size of a G9 ?

Comment #2

As Dave said: all other things being equal, more pixels = smaller pixels. A smaller pixel collects less light than a large one, so the noise (uncertainty) is greater because the signal has to be magnified more (like turning up the volume on a small radio to equal the volume of a more powerful one - you amplify the hiss as well). Noise reduction using software is perfectly possible but requires averaging of information over adjacent pixels, i.e. effectively loss of resolution, so you're back where you started..

A useful rule of thumb is that for a picture held in your hand, if you have good eyesight, you can resolve a maximum of 300 pixels per inch. For a 6MP camera (3000 x 2000 pixels) this amounts to 10 x 7 inches, viewed close up (a foot away). Would you look at a print that size close up? If you hang it on the wall and look at it from a metre away, a maximum resolution of 200 pixels per inch is more likely, allowing a 15 x 10 inch print. For a 12MP camera the area would double, i.e. linear dimensions of about 20 x 14 inches..

Many posters on this forum have said that they get good poster-size prints (30 x 20 inches) from 6 MP cameras, which equates to a linear resolution of 100 pixels per inch. How close to a picture would you have to stand in order to be able to see detail of 0.01 inches? Probably closer than you ever would to a picture that size..

6MP is seen by many as a happy medium - enough pixels to give sharp pictures under any 'normal' circumstances, and few enough pixels to keep the noise down. I'd prefer 6MP with a large sensor compared to 12MP on a small sensor in a compact camera any day. The quality of the lens is also just as important - no point having lots of pixels with a modest lens that can't resolve detail that fine..

Bottom line: don't worry about pixels, unless you are planning to make extremely high quality pictures to hang in a gallery, in which case you will probably be using a medium format film camera anyway. All of todays cameras have more than enough. The G9 has a good reputation and apparently gives high image quality... which is all that matters..

Best wishesMike..

Comment #3

Commercial printing is done at 300 dpi or greater. For an 8x10 at 300 dpi, you need 8 megapixels to allow for very minimal cropping. Most of us are satisfied with somewhat lower resolution and find that 5 or 6 megapixel prints are acceptable. The G9 will allow you to print considerably larger but for really large posters the resolution will be poor..

Large DSLR cameras gather a lot of light onto a relatively large sensor. The small sized cameras gather much less light onto considerably smaller sensors. This is a minimal problem for daylight photography. The G9 will come close to the quality of a DSLR for your trout stream pictures. The G9 and other small sized cameras do not do well indoors especially with natural lighting. When the small pixels try to amplify the low light, noise can occur.

Some people believe that the small cameras should be limited to about 6 megapixels. I don't. First the 12 megapixel G9 does exceptionally well with good lighting. There are plenty of small 6 megapixel cameras. Some do slightly better under low light conditions but the difference is really minimal.

If you want the best camera for low light situations you will need not only large pixels but a full sized camera with full sized optics. That means a DSLR. With the current sensor technology, small cameras just don't do well under these conditions...

Comment #4

The G9's 1/1.7" sensor's pixel pitch is around 1.9 microns. That means it'll be diffraction limited at about F/6 - ie. a perfect lens would soften above about F/6..

It'll have something like 3 times as much noise per pixel as a DSLR with a 5-6 micron pixel pitch..

However, it is pretty darned good for a compact camera..

A 1/1.7" sensor camera with 6mp might be a little better compromise (Fuji F-series); ~1.4x less noise per pixel, while softening above about F/4..

This all doesn't matter much if you've got a lot of light available; use the lowest ISO & widest aperture available as a starting point (best for a perfect lens)...

Comment #5

It's worth pointing out that the improvement would have been even greater if you had shot RAW and converted to a lossless format such as PSD or TIFF, and upsampled that..

Dave Martin wrote:.

When printing your picture as a poster it is often helpful toartificially increase the pixel count by interpolation to avoidunsightly pixelation. The following clown's nose shows what I mean -doubling the pixel count in each direction on the photo added noinformation, but made the image smoother..

Image control:Zoom outZoom 100%Zoom inExpand AllOpen in new window..

Comment #6

It's not just the pixels because the lens, subject, software and printer (and the printer's software and driver) all come into it..

If worried about the camera, why not download the original of one of the review samples (get one like your pictures will be) and get it printed or print it as a poster? It may cost a bob or two but that's nothing compared to the cost of the camera..

BTW, by poster do you mean a collection of papers stuck together (which works well based on my experiments with a Leica or Olympus and Epson printer) or a large sheet of paper printed in one go?.

Other than Epson's software for posters there's a shareware program called "ProPoster" which simply does what it says on the box. Meaning that it will split a picture up into sheets and then print them for assembly. The Espon one is easiest to use but the ProPoster one gives you more control over sizes..

The trick with mounting sheets of paper as a poster is to look at the direction of the light and arrange the overlaps consistently, so that the bare edge of the paper is in shadow. Think of tiling on a roof... I have several examples, from the experiments around the house, and no one has commented: with one exception a pro designer turned art teacher/lecturer at a nearby college..

Hope this helps, David..

Comment #7

David Hughes wrote:.

The trick with mounting sheets of paper as a poster is to look at thedirection of the light and arrange the overlaps consistently, so thatthe bare edge of the paper is in shadow. Think of tiling on a roof....

I've done this another way. Set them up the way you describe, fixed temporarily with removable tape on the back. Use a generous amount of tape so the sheets won't move around. Then turn the whole thing face-down and with a brand-new blade, cut through both sheets at the overlap, remove the waste and butt together. The joins are close to invisible that way..

Cutting from the back is important - I stole the technique from marquetry, it works pretty well...

Comment #8

And if you want posters the size of a billboard you can give the rasterbator a try..

Http://homokaasu.org/rasterbator/.

David Hughes wrote:.

It's not just the pixels because the lens, subject, software andprinter (and the printer's software and driver) all come into it..

If worried about the camera, why not download the original of one ofthe review samples (get one like your pictures will be) and get itprinted or print it as a poster? It may cost a bob or two but that'snothing compared to the cost of the camera..

BTW, by poster do you mean a collection of papers stuck together(which works well based on my experiments with a Leica or Olympus andEpson printer) or a large sheet of paper printed in one go?.

Other than Epson's software for posters there's a shareware programcalled "ProPoster" which simply does what it says on the box. Meaningthat it will split a picture up into sheets and then print them forassembly. The Espon one is easiest to use but the ProPoster one givesyou more control over sizes..

The trick with mounting sheets of paper as a poster is to look at thedirection of the light and arrange the overlaps consistently, so thatthe bare edge of the paper is in shadow. Think of tiling on a roof...I have several examples, from the experiments around the house, andno one has commented: with one exception a pro designer turned artteacher/lecturer at a nearby college..

Hope this helps, David..

Comment #9

...figure pixel size?.

Beegle wrote:.

Do you know the pixel size of a G9 ? .

No. But they are tiny. Go figure it out yourself?.

Click on the "Camera Database" link in the upper-left...click on "Canon"...clickon the picture of the G9...note the "Max Resolution" and "Sensor Size". The "Sensor Size" will be given as a stupid fraction such as 1/1.7". You will have to click on "Learn/Glossary"...click on "Camera System"...click on "Sensor Sizes"...scroll down to the table and note the actual dimensions of the stupid size sensor in the G9. It will be something like 7.6mm x 5.7mm. Then divide the horizontal size by the horizontal resolution, whihc was probably something like 4000 pixels. That will give the pixel pitch: 7.6mm / 4000 = 1.9 microns..

The important factor is NOT the pixel pitch, but rather the photosite area. So do the same calculations in the vertical dimension: 5.7mm / 3000 = 1.9 microns. They are almost always the same! Then, multiply 1.9 x 1.9 = 3.61 square microns..

This is a simplistic analysis. It ignores "fill factor", which is the % of the photosite area that actually senses light. Small sensors can have pretty poor fill factors! However, some small sensors have "micro-lenses" above all the photosites. These lenses compensate to some extent for the "fill factor". The G9 is a high-end camera, so it probably has "micro-lenses". Manufacturers don't advertise their "fill factor"..

BTW, I have been asking Phil to include Pixel Pitch and Photosite Area in the specifications for 2 years. He could also ask manufacturers to specify whether micro-lenses are used and what the effective fill factor is. Lastly, he should include all these data in the Buying Guide, so that you could search for all cameras that have photosites of at least 4 square microns and don't have micro-lenses (which are implicated in cases of PF). But no! .

Charlie DavisNikon 5700 & Sony R1HomePage: http://www.1derful.infoBridge Blog: http://www.here-ugo.com/BridgeBlog/..

Comment #10

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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