print size vs megapixels vs quality question

[Qarik]

I printed out an 11x14 shot through smug mug. It turned out okay but a little more grainy then i was expecting. I went back and retraced my cropping/settings on this picture. It appears the shot was heavily cropped..I only have maybe 6 megapixels in the shot.

Well that is my 1st question..for say family portrait..is there some kind of rule of thumb with regard to number megapixels and print size? Is 6 mpixels too little for an 11x14?

And what compression quality do you use for jpegs? I was using 80% and 240dots per inch. The jpeg looked fairly close to the lightroom shot. I think I will up it to 300 dots per inch and 100% for quality.

I also recall seeing a smugmug option in some control panel "sharpen for printing" or something like that...I might be imagining things though.

[pathfinder]

I printed out an 11x14 shot through smug mug. It turned out okay but a little more grainy then i was expecting. I went back and retraced my cropping/settings on this picture. It appears the shot was heavily cropped..I only have maybe 6 megapixels in the shot.

Well that is my 1st question..for say family portrait..is there some kind of rule of thumb with regard to number megapixels and print size? Is 6 mpixels too little for an 11x14?

And what compression quality do you use for jpegs? I was using 80% and 240dots per inch. The jpeg looked fairly close to the lightroom shot. I think I will up it to 300 dots per inch and 100% for quality.

I also recall seeing a smugmug option in some control panel "sharpen for printing" or something like that...I might be imagining things though.

300 pixels per inch X 11 inches = 3300 pixels for the short dimension

300 pixels per inch x 14 inches = 4200 pixels for the long dimension


3300 x 4200 = 13, 860,000 pixels or ~ 14 Mbytes

So 6MPxls is a bit short without uprezzing. But if your shoot in RAW, it is easy to uprez a bit in Adobe RAW converter before popping your image into Photoshop.

Having said that, lots of folks have printed images at 11x14 from a 6 Mpxl camera. I have a number of images from a Canon 10D that was 6,5 MPxls (http://www.dpreview.com/reviews/CanonEOS10D/page2.asp)
This image came from my Canon 10D several years ago. I have it framed on the wall in my home at 11x14 inches and it is grainless

http://pathfinder.smugmug.com/photos/404480349_esoxp-L.jpg

The secret is the quality of the pixels and avoiding cropping the image if you can.

What was the ISO your image was shot at?


Here is a tute I wrote about Resolution and printing. (http://pathfinder.smugmug.com/gallery/2246604_CgPjC)

I save jpgs at a Image quality of 10 in Photoshop, or 90% in LR2. I prefer to print at 300 pixels per inch, but have seen a number of fine prints printed at 180 ppi. Remember, ppi does not equal dots per inch from your printer. EACH pixel may be represented by 5 - 10 dots per inch out of an inkjet printer.

I usually print from Lightroom2 now, I like it better than the dialogues in Photoshop, and sharpen maximally in the printing module in Lightroom. I also do capture sharpening in LR2 RAW processing or in ACR 5+ before introducing my file to Photoshop.