How to calculate print sizes Photographer

/ 1 decade ago (13 June 2007 10:31)

Hi my friends. Today I want to tell, for those who do not know already how to calculate maximum print sizes, depending on the size of the digital image you produce. Bear in mind that the standard "ppi" - pixels per inch - for "photo quality" prints, is 300 ppi's. Also a big discussion is being held in several foruns I participate and also talking with professional printers, wether a file for printing shall be a TIFF or a HIGH QUALITY JPEG. But first for print sizes. A megapixel is 1 million pixels.It's an area measurement like square feet.
For instance,a 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".
As for TIFF vs HQJPEG's, if I would print at home for a "true photo quality" printing, I would use always a TIFF file, as all the image information is not compressed or lost. However, I learnt that when printing outside, in a professional printing lab, an HQuality JPEG ( 12 compression number in Photoshop, the less compressed one )do make EXCELLENT results. However also learnt that if we want to publish our captures in a magazine or a book, TIFF is allways the best option. Hope this info was helpfull to all of you. GT. Photographer

Post replies:

1 decade ago (18.06.2007 06:43)
Reply by:
Fred, be advised that DPI is different than PPI.Even though "dots per inch" (dpi) and "pixels per inch" (ppi) are used interchangeably by many, they are not the same thing. Traditional printing methods use patterns of dots to render photographic images on a printed page. While pixels on a monitor are square and in contact with the adjacent pixels, printed dots have space between them to make white, or no space between them to make black. Color photographs are printed using four inks, Cyan, Magenta, Yellow, and Black (CMYK), and four separate dot patterns, one for each ink. Dots per inch (dpi) refers to printed dots and the space between them, while pixels per inch (ppi) refers to the square pixels in a digital image. Keep in mind that many companies will ask for images at 300dpi when they really mean 300ppi. A digital image is what it is. It is however many pixels wide by however many pixels tall. If you divide each dimension by 300, you will have the size of the image at 300ppi. Now think about 300 pixels in an inch of space. Each pixel could be black, white, or any other color, but they are all next to each other with no spaces between them. When a digital image is prepared for reproduction on a printing press, pixels are converted to dots. Dots have spaces between them. 300 pixels become 150 dots and spaces, so 300ppi becomes roughly 150dpi. 150dpi is the accepted standard for printing photographic quality images.Printers usually refer to the number of rows or lines per inch (LPI). 150 lines per inch is simply 150 rows of 150 dots per inch. 150 LPI and 133 LPI have long been the established standards for the best quality reproduction of photographs in books and magazines. Newspapers traditionally use 85 LPI for photographs and detail is lost because the dots are plainly visible.Source: studio toolbox Photographer
1 decade ago (18.06.2007 10:36)
Reply by:
Thanks... :-)
1 decade ago (15.06.2007 11:28)
Reply by: sed
I just recieveved a Print catalog that asks for 350 pix.... Is that too tight?? Cool
1 decade ago (16.06.2007 05:26)
Reply by:
It depends on the final size, Sed... Photographer
1 decade ago (16.06.2007 05:43)
Reply by:
I have a 8.1 megapixel but as you know my friend, the image sensor is in question. I will eventually have a large print made to hang on my wall. I have not decided which one. Grin Photographer This is very useful information, the formulas that you provided have educated me... thanks!
1 decade ago (16.06.2007 05:58)
Reply by:
My only question is what do the photo guys that do the prints do my default. I would bring my card, order by touchscreen, wait an hour and get the prints. The DPI thing - I have to say - I was totally ignorant to.
1 decade ago (16.06.2007 05:58)
Reply by:
that is "by default" not "my default" my typing continues to stink!! Amazed
1 decade ago (16.06.2007 08:17)
Reply by: Alfa30
Thanks Artur... Grin