Megapixel Chart explains the Megapixel Myth

[Bob Varipapa]

Interesting article --

Megapixels Chart
v1.0, 2005.12.26

Each colored box represents a certain number of megapixels. The numbers along the top and left side are print dimensions in inches at 300ppi (pixels per inch). Most books and magazines require 300ppi for photo quality. For example, the chart shows that you can make a 5" x 7" photo quality print from a 3 megapixel camera.

inches @ 300ppi (numbers inside colored boxes are megapixels)



Notice that as the print size doubles, the megapixels required increases exponentially. You can make nice 8" x 10" prints with a 6 or 8 megapixel camera, but to make a true photo quality 16" x 20" print, you need between 24 and 30 megapixels. Don't be fooled by manufacturers' claims that say you can make 16" x 20" prints from an 8 megapixel camera. While you certainly can make a print that size, it will not be true photo quality.

Here's why:
A megapixel is 1 million pixels. It's an area measurement like square feet.

A typical 8 megapixel camera produces images that are 3266 x 2450* pixels.

If you multiply 3266 by 2450, you get 8,001,700 or 8 million pixels.

To find the largest photo quality image you can print, simply divide each dimension by 300:

3266 / 300 = 10.89 inches
2450 / 300 = 8.17 inches

If you are not publishing your images in a book or magazine, and you're just making prints for yourself or your friends, you can "cheat". Good quality inkjet printers can make a nice looking print at 250 or 200ppi. At 200ppi, the maximum print size becomes:

3266 / 200 = 16.33 inches
2450 / 200 = 12.25 inches

If you know how to use image editing software like Photoshop, you can "cheat" even more by increasing the image size, and even doubling the number of pixels in the image. The quality of the camera and lense becomes more important at this point bacause any loss of detail or sharpness is magnified. If an image is enlarged too much in this manner, it will look "fuzzy" or "pixelated".

http://design215.com/toolbox/megapixels.php

http://duggmirror.com/design/13_Phot...egapixel_Myth/

[DonLashier]

Originally Posted by Bob Varipapa

If you are not publishing your images in a book or magazine, and you're just making prints for yourself or your friends, you can "cheat". Good quality inkjet printers can make a nice looking print at 250 or 200ppi.

Most magazines actually print at 150 lpi but typically request images at twice that resolution (in dpi). My experience has been that printing on an inkjet you'll get comparable quality at 160 dpi. I've done tests and see very little if any difference between 240 and higher, and 160 is nearly as good. So for your own printing imo you can go considerably (nearly twice) the size mentioned in the article and still get "photographic" quality prints.

But you're right about the "allusion" of megapixels due to the squaring factor. It takes 4x the megapixels to make a noticible difference. That's why I'm still happy with my 1D (4MP) which prints just fine at 12x18 and waiting for higher DR which will be much more significant wrt image quality. I do wish at times that I had a little more cropping flexibility however.

- DL

[Gavin]

I do understand what your saying, however I know from experiance that you can get a great 16x20 from an 8 megaoixel camera, and it looks like a true photograph. I don't feel it matter much anymore. The quality is so good not that the average persons eye can no way tell the difference, and that's good enough for me. Although more is still better, so I'm glad to see the megapixels climb.

[DonLashier]

Originally Posted by Gavin

I do understand what your saying, however I know from experiance that you can get a great 16x20 from an 8 megaoixel camera, and it looks like a true photograph.

Eye resolution at a reasonable distance is around 100 dpi so this is not surprising. As I said in my previous post, 150 to 160 dpi is more than adequate unless you're using a loupe. All the rest is marketing hype, or confusion because of the 2x requirement for offset.

- DL

[GregScheidemann]

Exactly Don, and a file for magazine doesn't need to be more than 150 dpi in resolution, as long as you interpolate it up to 300 dpi before submitting it. They can't produce anywhere near 300 dpi with their 150 lpi screens, but you do need to submit a 300 dpi at the full size of reproduction, to avoid to possibility of moire appearing due to the 'phasing' to the two resolutions (150 dpi and 150 lpi) matching up in odd ways.

So many people in the magazine world have been told that interpolating is a TERRIBLE thing to do because you are 'creating information' and that it can never be as good as the original. but the truth is, they can't hope to reproduce even the 150 dpi of detail. The only reason for 300 dpi is to avoid the moire by being double the lpi resolution. But upresing to 300 dpi is important.

I'm sure a LOT of full page photos in Sports Illustrated were created by the Canon 1D, and that was only 4mp. According to this chart, you could only go half page with that file.

greg

[diglloyd]

Originally Posted by Bob Varipapa

Notice that as the print size doubles, the megapixels required increases exponentially. You can make nice 8" x 10" prints with a 6 or 8 megapixel camera, but to make a true photo quality 16" x 20" print, you need between 24 and 30 megapixels. Don't be fooled by manufacturers' claims that say you can make 16" x 20" prints from an 8 megapixel camera. While you certainly can make a print that size, it will not be true photo quality.

[No offense is intended at the poster here, but I can't hold back on my view of this post]

I guess museums and collectors will now have to throw out many of their crappy photographs from past masters (not true photo quality, the resolution is too low).

35mm slides, resolving at best 70 lp/mm on film (less when scanned and printed) are only good for about 17 X 11 prints. Frans Lanting's photograph (taken on 35mm film) displayed at Calypso Imaging in Santa Clara at 6 X 4 feet had me fooled--I thought it was simply stunning when I viewed it.

IMO the technical “analysis” (from the Latin “to pull from one's ****”) is ludicrous for anything of artistic merit.

On the technical side, the megapixels do not increase exponentially; they increases as the square. Quite different things. In mathematical “ big O” notation, megapixels increase as O( w*h ), not O( 2^(w*h) ), where 'w' and 'h' are the width and height. Resolution increases linearly with the width or height.

I think the guideline has a moderate correlation with print quality, but is otherwise useless nonsense, based on the myth that resolution equals quality.

Color resolution, contrast, low noise, aliasing and other artifacts contribute as much or more than resolution to perceived print quality by the human eye.

If this were not true, my 10-megapixel Panasonic Lumix LX2 would make just as good a print as my Nikon D200. I'll put a 4MP Nikon D2h file up against a 10-megapixel digicam any day. I have a 20 X 30 print made with a D2h, cropped to 3MP which is gorgeous. Consumer digicams, with their "high resolution" look like crap at that size (and that's assuming the lens was even able to resolve to the demands of the sensor!).

[Bob Varipapa]

No offense taken. I didn't write the article and have enjoyed (and learned) by reading everyone's comments.

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