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Megapixel to print size formula?

h1r0ll3r

h1r0ll3r

macrumors 68040
Original poster
Dec 28, 2009
3,920
19
Maryland
I'm wondering how one goes about figuring out what the max size photo I can print based on an image's megapixel size? Is there some formula for this or what? Basically, if I had a 10 MP image/photo the max photo size it can be printed out would be ____. If I had a 14MP image, it could be printed up to X size etc. Always wondered this but never thought to ask :eek:
 
The simple answer is you can print as big as you want (or can afford!) as long as you are looking at the print from far enough away.

The more involved answer assumes you want to print at the maximum resolution of the printer. Assuming 6 Megapixels (because the math is easier) and a 3:2 aspect ratio, thats 3000 pixels by 2000 pixels. If the printer does 300 dots per inch (typical) that would be 6 2/3" x 10".
 
Yes, but it's not as straightforward as that.

I've produced A1 glossy prints from a 6mp RAW file without problems - but the camera was a pro Nikon. In the real world the quality (size) of the sensor is rather more important than the number of pixels.
 
I'm assuming shot in focus, steady camera, decent lens, exposure within range of sensor. Otherwise all bets are off for a good print of any size!
 
That whole 300 ppi guideline is something people really need to start ignoring. It's not true anymore, and there's a lot more to that golden rule than just a number. The resolution of anything depends on the distance from which you're looking at it.

Anyway, you'd only need to print an image at 300 ppi if:

1. Everyone who views your print is going to be looking at it from less than 30 cm/12 inches away. That's what really high-end fashion magazines probably assumed.

2. They all have perfect vision.

3. Your printer is ancient and only does like 600 dpi or something (or lets say every pixel is created using only 2 - 4 dots)




In Imperial units, I believe the general rule is:


pixels per inch = 3600/(viewing distance)

Mind you, viewing distance is in inches. ;)
 
I've printed 3~4 MP photos at 30x45 cm^2 without any problems. As the others have said, you have to factor in the viewing distance and the material. If you print to canvas (which has a rough texture), for instance, you will not attribute the lack of sharpness to the source material, but to the material you print on. Depending on the photo, this may be very pleasing -- or not. If, on the other hand, you print on glossy, you tend to notice the difference between a higher MP source material much more.
 
I have heavily cropped pics from my old D.Rebel (10MP I think) printed 16x20. Cropped image must have been around 3MP. Looks great but they are large portrait pics. Depends on your subjects, etc. I have seen very large prints from the first mainstream digital SLR (canon D30) which was a 3MP camera. They look fantastic.

There is no formula. It is trial and error. Too many variables. anyone else who says there is a formula doesn't know what they are talking about.
 
not to come up with a vague answer but...

I've printed a 6mp shot to 40x30inches.

I've also printed shots from the 6MB camera 4.5 - 5.5 feet tall too (it was on a truck wrap) you could see some fuzzies up close but at a 4-6 foot distance all looked pretty good.
 
OK, to elaborate a bit, I have a 12MP Canon SD780 IS point and shoot as well as an 18MP Canon T3i. What I'm looking to do is try and print out images as big as possible without losing image quality.

I've printed out pic from my P&S shoot up to 12x18 with some loss in image quality (the pics look like someone went ape ***** with the smudge tool in photoshop) It's not too bad however the image quality is less than desirable.

I figure I shouldn't have any issue with images from the T3i at that print size however I wanted to certain of this prior to printing out mass quantities of photos.

Basically, I want the images to look crisp and clear even if you're looking at the pic from 2 inches away. I'm pretty sure I'll need to get a better printer to accomplish this as well so that's definitely a possibility here too.
 
h1r0ll3r said:
I've printed out pic from my P&S shoot up to 12x18 with some loss in image quality (the pics look like someone went ape ***** with the smudge tool in photoshop) It's not too bad however the image quality is less than desirable.
Click to expand...
That doesn't have anything to do with the actual resolution, but the image quality of the camera: a point and shoot has a very, very small sensor, each pixel is much smaller, the optics is much cheaper, etc.
h1r0ll3r said:
Basically, I want the images to look crisp and clear even if you're looking at the pic from 2 inches away. I'm pretty sure I'll need to get a better printer to accomplish this as well so that's definitely a possibility here too.
Click to expand...
Then you better not print anything: unless someone is visually impaired, nobody will look at your photos from a distance of 5 cm.
 
h1r0ll3r said:
Basically, I want the images to look crisp and clear even if you're looking at the pic from 2 inches away. I'm pretty sure I'll need to get a better printer to accomplish this as well so that's definitely a possibility here too.
Click to expand...

Assuming your images aren't poor to begin with, printing at 300 dpi will be sufficient. If you need to print larger than that you can creep up to 200 dpi, but after that you will really suffer. There's generally nothing to gain past 300 dpi. I've printed at 600 dpi frequently and beyond. Most of the time a mid-range printer will just make it worse.
 
tersono said:
Yes, but it's not as straightforward as that.

I've produced A1 glossy prints from a 6mp RAW file without problems - but the camera was a pro Nikon. In the real world the quality (size) of the sensor is rather more important than the number of pixels.
Click to expand...

...and don't forget "The Glass"

With the DSLR vs the P&S debate, one always has the option to purchase better optics, as with your t3. This will, IMvHO, make the biggest and most immediate improvement to your IQ.

You bet, you can always pick up a nice, new fancy printer...and the 8 ink package that'll cost ya:) As well...the maintenance to take care of the inks (if your aren't always using it consistently)...et al. OR, give one of the many, dozens of excellent print shops on line a try. I've used WHCC for a couple years and LOVE their quality...but I've also had incredible luck locally, at ONE of my Target stores...there's a kid that's really in to quality pics that works there, and they have an excellent wide format printer. The other Target has the same printer but a staff that isn't nearly as interested. I think that's something you'll find if you try an online professional printer. As there is a ton of competition, MOST of them do a really, REALLY great job and offer prices that are very hard to beat on your own...with your 9500mk2 or your 3880 and their 8 ink packs!

Seriously...I speak from experience. I've not yet picked up one of the latest Epsons...as I've found that for the amount of time I need to print larger than 11x17...it's not worth the cost, space, nor maintenance of owning a high end printer. In fact, after 20 years of shooting and either taking in for development, doing my own at home, or sending away...I've come to the conclusion that the actual "Print Process" is an Art of it's own...kind of like photography;)

J
 
akdj said:
You bet, you can always pick up a nice, new fancy printer...and the 8 ink package that'll cost ya:) As well...the maintenance to take care of the inks (if your aren't always using it consistently)...et al. OR, give one of the many, dozens of excellent print shops on line a try. I've used WHCC for a couple years and LOVE their quality...but I've also had incredible luck locally, at ONE of my Target stores...there's a kid that's really in to quality pics that works there, and they have an excellent wide format printer. The other Target has the same printer but a staff that isn't nearly as interested. I think that's something you'll find if you try an online professional printer. As there is a ton of competition, MOST of them do a really, REALLY great job and offer prices that are very hard to beat on your own...with your 9500mk2 or your 3880 and their 8 ink packs!
Click to expand...

A couple of years ago about a dozen photographers (mostly advanced amateurs but also a couple pros) in the Portland, OR area had a "get-together" and we discussed making prints. it turned out that almost everyone was using Costco! You can get the printer profile and DPI info and export sized and color corrected for the printer. Worked great, but I haven't printed anything in over a year.
 
Should've mentioned that, thanks Talmy.

I've also had excellent luck at one of our local Costcos (I haven't tried the other)...as have a few friends (mix of pros and ams) in town. Good point. Wal Mart in some cases as well...I've heard. Most of these shops (big Box stores) have excellent printers...it's mainly about who's running them:)

One pretty good option is the Canon Pro9000mkII right now...under $400 with a a set of ink included...and not too spendy when you have to refill, as you can buy the individual colors. It's another 8 ink cart machine and can print 13x19 or up to 13x23...right now, a hundred dollar discount at B&H, and sometimes you can get them for next to nothing with the purchase of a new body from Canon

Here's the link at B&H for $350...and check out the review...over 300 with an average of 4.5 out of 5 stars...it's a really nice printer to start out with as a photographer...instead of jumping in to the 9500 or 3800(80) series from Epson.

http://www.bhphotovideo.com/bnh/controller/home?O=&sku=609356&Q=&is=REG&A=details

But again...definitely look around locally, because it is an art itself and can take some time to fine tune, match up profiles with your monitor, etc.

Back to the OP's original question though...I'm just not sure there's an "Exact" answer to your query. Especially considering the difference in "Sharpness" necessary for what you're shooting. People and portraits, you don't need to super sharpness...as you would for perhaps a deep landscape shot. Lots of variables. Most 10+ megapixel DSLRs these days are quite capable for up to 20x30 sizes, IF you practice good shooting technique, tripods, mirror lockup, and use the correct gear.
Good luck

J
 
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