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What is the rule-of-thumb relation between megapixels and printout size?

If I have a camera with that number of MP I will be approximately be able to print solid xx by yy inch (or cm) photos?

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marked as duplicate by AJ Henderson, Michael Clark, MikeW, mattdm, Paul Cezanne Feb 13 at 20:23

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

    
@AJHenderson - Reading it right now, although it might take me a while for that. Not sure about it being a duplicate, but interesting read nevertheless. This was more asked from a perspective, "how much MP should a camera have if I want to make prints the size of __?" All other things being equal. –  ldigas Feb 13 at 16:50
    
is that not the one with the equation in it? If not, then I suggested the wrong one. We have a question floating around that has a table and an equation for resolution to print size. –  AJ Henderson Feb 13 at 16:51
    
Ah, here it is: photo.stackexchange.com/questions/456/… –  AJ Henderson Feb 13 at 16:53
    
@AJHenderson - Ah, that's the one! Had a feeling I saw it answered here somewhere, but just couldn't find it in the results. Yes, this can now be closed as a duplicate. Or deleted, what is more proper? –  ldigas Feb 13 at 17:01
1  
I'd say close as duplicate, that way the question is easier to find. Duplicates make useful tombstones as long as the answers don't get divided up across multiple instances of the same question. –  AJ Henderson Feb 13 at 17:03

2 Answers 2

Ken Rockwell has a really good overview of this:

http://www.kenrockwell.com/tech/mpmyth.htm

My general take: Most modern camera can take really good images that print at most common sizes. If you want to print really large (> 30" on the long size) you might need to be more careful about image selection and preparation, but I print at 13x19 regularly with images taken with some cropping without problem.

One thing that's forgotten is that in general, larger prints are going to be viewed further away so they don't need as much detail, so they can be printed with a lower pixel-per-inch value. It's always nice to take a gigapixel panorama and print it out so you can do the "where's waldo" on a 40x30 print with a magnifying glass, but in the real world, that rarely happens.

If you do have a print that simply doesn't have enough pixels to print well at a given size, you still have options. Photoshop's image resizing command works pretty well as growing an image, and there are various third party tools/plug-ins you can use. When I need to ramp up the pixel count or optimize an image to a specific size/usage pixel density I use the one from onOne and I think it works very well most of the time (some images simply can't be saved).

So the short answer is, try for at least 150 pixels per inch on larger prints and you'll do fine. There are tools to help if you are running short, but honestly, what I do is print the thing out and study the results, and I only go into corrective measures if the print isn't good. We can talk about tech details all we want, but what matters is how it looks on paper, so what you need to do is print it, study it, and then decide if you need to improve the print...

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+1 for "larger prints are going to be viewed further away". –  Philip Kendall Feb 13 at 19:55

Print labs typically accept a minimum of 100ppi for printing. More is better, up to 300ppi. We have been able to do a 60" print from an iPhone photo and it came out fantastic.

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So how did you do a 60" print at 100 ppi from your 8 Mp (~3.2k x 2.5k) iPhone? –  Philip Kendall Feb 13 at 19:59

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