PhotoCamel - Your Friendly Photo Forum - View Single Post - Help needed with cropping and sizing for Prints

verdesardog · 07-18-2009

There are two distinctly different things that you are talking about, Document size (physical deminsion) and Pixel Dimensions (Number of pixels). They are inter-related, if you change one while keeping the other the same you will be changing the Resolution, Pixels per Inch or PPI.

Look at the image size info in photoshop there is pixel dimension (pixel width and pixel height) and Document Size (physical width and height). What gives you the resolution (ppi) is the total pixel count in association to physical size.

If you keep the pixel count the same but change the document size you will change pixels per inch (ppi), if you keep the document size the same while changing the pixel count you will change the ppi.

Pixel dimsion, document size and resolution are all inter-related and dependant on each other. You can change the document size without changing the pixel dimension, you can change the pixel dimension without changing the document size but in both cases the resolution will change.

PPI and DPI are both a measure of density, ppi could be considered as electronic density while dpi is physical density. The relationship with ppi to dpi needs to be considered when printing. For optimum printing you want to put as many dots of ink on the paper as you can per pixel of picture file. If your printer prints at 1200 dpi and uses 6 colors of ink your photo will print optimally at 200 ppi so that your printer can use all dots of ink per pixel of file. (6 drops of ink X 200 ppi = 1200 dpi).

Anyway don't get PPI and DPI mixed up, they are NOT interchangable, PPI is the density of your file and DPI is the density of your printer. When you send your files out to be printed your PPI has to be optimum for the printers DPI. Your lab should tell you what PPI they desire for printing. When they do, give them that PPI @ the document size you want printed. A file to be printed 4x7 will need much fewer total pixels than a file to be printed at 8x10, but they need to both have the same PPI.

Is this as clear as mud now?

07-18-2009	#20 (permalink)
verdesardog F1 Camel Location: Arizona Posts: 3,055 CamelKarma: 12104 Editing OK?: Yes Gallery \| Blog	Re: Help needed with cropping and sizing for Prints There are two distinctly different things that you are talking about, Document size (physical deminsion) and Pixel Dimensions (Number of pixels). They are inter-related, if you change one while keeping the other the same you will be changing the Resolution, Pixels per Inch or PPI. Look at the image size info in photoshop there is pixel dimension (pixel width and pixel height) and Document Size (physical width and height). What gives you the resolution (ppi) is the total pixel count in association to physical size. If you keep the pixel count the same but change the document size you will change pixels per inch (ppi), if you keep the document size the same while changing the pixel count you will change the ppi. Pixel dimsion, document size and resolution are all inter-related and dependant on each other. You can change the document size without changing the pixel dimension, you can change the pixel dimension without changing the document size but in both cases the resolution will change. PPI and DPI are both a measure of density, ppi could be considered as electronic density while dpi is physical density. The relationship with ppi to dpi needs to be considered when printing. For optimum printing you want to put as many dots of ink on the paper as you can per pixel of picture file. If your printer prints at 1200 dpi and uses 6 colors of ink your photo will print optimally at 200 ppi so that your printer can use all dots of ink per pixel of file. (6 drops of ink X 200 ppi = 1200 dpi). Anyway don't get PPI and DPI mixed up, they are NOT interchangable, PPI is the density of your file and DPI is the density of your printer. When you send your files out to be printed your PPI has to be optimum for the printers DPI. Your lab should tell you what PPI they desire for printing. When they do, give them that PPI @ the document size you want printed. A file to be printed 4x7 will need much fewer total pixels than a file to be printed at 8x10, but they need to both have the same PPI. Is this as clear as mud now?
	__________________ Michael COMMENTS, CRITIQUES ALWAYS WELCOME YOU ARE THE ANGEL FOR WHOM SOMEONE WAITS TODAY