Digital cameras forum: How Many MegaPixels for Large Blow Ups

Almost nobody can tell the difference between a 10MP 16x24 and a 13MP 16x24. Here are the articles and an excerpt.

http://www.nytimes.com/... .../08/technology/08pogue.html?_r=1&ref=technology

http://pogue.blogs.nytimes.com/... .../15/deconstructing-the-megapixel-myth/

From the article:

"I created three versions of the same photograph, showing a cute baby with spiky hair in a rowboat. One was a 5-megapixel shot, one was 8 megapixels and one was 13.

I asked 291 Digital, a New York graphic imaging company whose clients include ad agencies and fashion companies, to print each one at a posterlike 16 by 24 inches. (They were digital C prints, printed on Durst Lambda at 400 dpi, if that means anything to you.)

We mounted the three prints on a wall in Union Square in Manhattan. Then, cameras rolling, we asked passers-by if they could see any difference.

A small crowd gathered, and several dozen people volunteered to take the test. They were allowed to mash their faces up against the print, step back and squint, whatever they liked.

Only one person correctly identified which were the low-, medium-, and high-resolution prints. Everybody else either guessed wrong or gave up, conceding that there was absolutely no difference. "

The photos shown were 5MP, 8MP, and 13MP. Out of several dozen people, only one was able to distinguish which ones were the lower resolution and which one's were the higher resolution. All photos were printed at a professional printing store at 400dpi. I would think someone would be able to get up close and see a difference between 13MP and 5MP, but nobody was able to, except for one.

The links I posted didn't work right, but here's the original article.

http://www.nytimes.com/2007/02/08/technology/08pogue.html

Yes, thank you, I read it. I agree with the article. However, for every study or experiment, you have to look at the purpose and methodology, and the pitfalls. The purpose of the study is to prove to readers that upgrading from 5 or8 MP to 13 MP may not make a lot of difference about the print quality of the photos. In other words, upsizing MP is not the main ingredient to improve your photo quality, and I absolutely agree. However, this study is not designed to find out what MP gives the best print quality at 16x24 size, or even bigger. If you pay close attention, the resolution of these cameras stay at the lower quality print at 16x24 size. Again as pointed out previously, true photo quality is 300 ppi whereas 150 ppi is at the lower print quality. The 5-13 MP cameras all have print quality at or below the 150 ppi resolution level for 16x24 size. For the human eye, it is not easy to distinguish between 300 ppi vs 200 ppi (a 100 ppi difference). So it follows that it is not easy to distinguish print quality between 110 vs 175 ppi (between 5 MP vs 13 MP cameras), but a small number of people may be able to, and this is what the news article found too, not surprisingly.
Another important thing to consider is that the quality of the photo also may affect how easy you notice a difference when you enlarge a photo. My experience is that if I have a good shot with good lighting and tact sharp focus, I can enlarge or crop heavily and still get a good enlargement. But if the photo is taken at high ISO with digital noise or if the focus is slightly off, then the same enlargement will look horrible. Why? If the image is near perfect, our brain usually will fill in some of the blanks, kind of like an automatic interpolation. However, if it has defects, we will be more likely to spot them and notice the difference. In the NY Times study, the photo is taken by a professional, likely a pretty good near perfect photo, so it becomes more difficult for an average person to spot the difference. But if you have a less than perfect photo, your large print will definitely look better in a higher MP camera at 300 ppi resolution than at 150 ppi resolution.
But how practical is getting a camera to give high 300 ppi resolution at large prints? Not at all. And that is what I am trying to demonstrate in my original post (with some sarcasm using outrageously priced cameras as examples). It does not make sense to upsize your camera to get the true photo print resolution, and most people do not need to anyways. Does that mean that high MP cameras are useless? No. It is very useful if you crop a lot or if you routinely do a lot of large prints for a living. For the rest of us, upgrading to a higher MP camera does not make a lot of sense, especially if the upgrade is only a few MP more (from 8 MP to 13 MP), it does not make a difference in print quality. You have to upgrade to 30MP plus to really see a difference, and that was my point.
In terms of image sharpness and quality, your camera sensor's high ISO performance, lens quality, lighting, focus, skill, etc play a much more important role than MP alone. I have made a pretty detailed comment in another thread about image sharpness:
http://forums.cnet.com/5208-7593_102-0.html?threadID=337979&tag=forums06;forum-threads

By the way, you keep mentioning 400 dpi print on your threads. I just want to comment that dpi (dots per inch) is the printer's output and has nothing to do with an image's resolution or print size. Pixels per inch (ppi)on the other hand represents the image resolution. For printers, anything 360 dpi is good, higher dpi mostly wastes ink and does not add much to the print quality (not noticeable to human eyes).

I understand that 400dpi is for print, and I brought it up to show that at the highest print quality(which some would ask what the output was) that there wasn't any difference. We've had to answer quite a few "why does my camera only take photos in 72dpi" here.

If you have ten megapixels or twelve isn't the real determining factor, but what resolution you use when you take that photo. If you only have 360 by 480 selected, it won't make any difference how many megapixels you have, it won't blow up well at all. However, if you select 3648 by 4800 resolution, it would use every one of the pixels and will blow up into next year and still look very sharp.

A few posters bring out some very good points. Viewing distance is another big determinant about how high a resolution you need on a print. It is true that bigger prints when seen afar do not need much resolution to look "good". The extreme example is large Billboards, those are printed in 10 to 20 ppi. For a 16x20 print, if your viewing distance is 3 feet away, you need only about 90 ppi to look good. But if you view it from 2 feet away, then you need about 150 ppi to look good. If you are a bit myopic (as one reader says) and look at it from 1 foot away, then 300 ppi may be needed.
And I agree with many posters that the composition and aesthetics of the photo is more important than the actual resolution, because we can always adjust our viewing distance to perfectly view and enjoy a good piece of art. Every person may have his or her preferred viewing distance, it is very subjective. And again my original intention is just to try to say that upsizing the MP is not the best or the only way to get a better looking large print. Often the cost does not justify the size increase. Yes you may have more room to crop. But you can also upsize the photo with software at much lower cost, if you don't think your image has enough resolution for the large print you want. Photoshop has its own bicubic smooth enlargement and there are also plug-in software as mentioned above.

You really only need 3MP for these uses because the highest you can go on a TV is 1080 line of resolution, which is 2048 1536. Really, most people have their resolution set on a computer screen where 1MP would be surpassing the resolution of the screen.

Yes, the good old days of having your own dark room and smelling those hazadous chemicals are mostly over. I'm not an expert in printing but has done some darkroom exposures years ago for my research publications. You have complete control in the process, but you need to be selective, otherwise you will be literally living in that black hole. Then came the era of 1 hr photolabs, and you can print everything you took but sometimes they come back crapy. Has the wrong color, brightness or even loss of sharpness. The self-contained photograph development equipment at these stores depends heavily on the skill of the operator. Each type of film has its own color profile and using the wrong settings will mess up the color. Since these are done in a large batch, the computer just chooses an average brightness of each image for printing, so that can sometimes screw up a high contrast photo, ending up with bad exposures. An inexperienced operator can even cause permanent harm to your film if they are careless in handling your film, exposing your film to outside light (this can be the case in some drugstores or small stores that do not have a real dark room, or the operator did not close the doors tight on the equipment). This can permanently degrade your photo.
Now fast forward to digital darkroom (meaning you sit in your own desk and printing your image off the computer to the printer). This process is also heavily dependent on the skill of the operator (meaning you or the place you deposit your memory card). First of all, your monitor and printer needs to be calibrated to match the color on the computer screen and the color output of the printer. There are many gadgets for this, including the Spyder3 and Huey, etc. Once calibrated, then you can start editing your photos (do not edit your photos before calibration). Then you have to decide how big the size of the print you are going to make for suitable adjustments of the resolution of the image if necessary, by doing upsampling or downsampling of your image with Photoshop, plug-in softwares, etc. Generally 300-400 dpi setting on the printer is more than adequate for a high quality photo print. If you just deposit your memory card in the drugstore, Target or Costco, then your photo is not going to look as good as you would have done them yourself at home (provided you know what you're doing). Why? because the operator of those places mostly do not know how to optimize your photos or printing. Most of them do not calibrate their machines, just print whatever is uploaded. Also, what you see on your computer monitor screen may not match up to what they see on theirs, so results are less reliable. Sending your photos to more professional photolabs always get better results no matter whether it is film or digital.
By the way, if you are interested in the resolution of scanned 35 mm film, I think it is slightly higher than a 16 MP digital camera, about 5380 x 3620, but you may need to double check on this. I have not had any time to mess around with scanning my old film photos yet.

I know the question is focused on digital, but has anyone suggested film? You can get a more-than-decent 16x20 with a 35mm camera....or you can go large format for far, far less than the need-to-sell-a-kidney price of the Hasselblad. I love my Canon digital, but I still think my Nikon film camera is great.