some advice on DPI please - re looking for a new laser printer

billy_bones · Aug 30, 2013

Hi,
I'd like some good advice on what sort of DPI to look for. I've been looking around for a colour laser printer and have a few questions about what resolution to get.

1. the pictures my camera takes is 300 DPI (dots per inch) when set on best quality, (which is what I use.) So far my research has shown this is what magazines will use and that any DPI above that on a printer will just be ignored and basically a waste. If so why do most printers go way above that often into the thousands?

2. could someone please explain the horizontal and vertical combination i.e. 600 x 300 DPI, surely it should print at the same quality in both the horizontal and the vertical? I'm either going onto the twilight zone here or am missing something that's probably obvious.

3. My old printer is a Canon Pixma MP160 with 4800 x 1200 DPI it is getting a bit old now (hence the search for a new one) but it has problems giving a decent print higher than a 6 x 4 photograph and that's on the best quality setting, using good paper and after going through the expensive rigmarole of cleaning the heads. saying this it is an inkjet printer can I expect better results from a laser printer? either with a lower, similar or higher DPI?

4. I have my camera set on "large" picture size. would choosing a smaller size have any difference on the print result?

and finally
5. just info people might need rather than a question really . . .
I use a Nikon D5100 set to best quality and large picture (as stated) total 16.9 million pixels / effective 16.2 million pixels (not sure what that difference is for but that's the specs.) I am looking to print some exceptionally good quality prints at 10 x 8 (more or less A4) pictures are at 300dpi what should I be looking at for the specs in a laser printer please?

any help would be appreciated
thanks B.B.

Ysarex · Aug 30, 2013

billy_bones said:
Hi,
I'd like some good advice on what sort of DPI to look for. I've been looking around for a colour laser printer and have a few questions about what resolution to get.

1. the pictures my camera takes is 300 DPI (dots per inch) when set on best quality, (which is what I use.) So far my research has shown this is what magazines will use and that any DPI above that on a printer will just be ignored and basically a waste. If so why do most printers go way above that often into the thousands?

The photos your camera creates are PPI (pixels per inch) not DPI (dots per inch). A pixel in a photo is not equivalent to a printer dot. The terms are sloppily used in the industry and lead to all kinds of confusion. When a printer puts a dot of ink on a piece of paper it has no ability to make that dot of ink darker or lighter. To create a range of continuous tone in a print a printer lays down a whole lot more dots than there are pixels in the photo. To get a range of tone covering 256 discreet steps from black to white (8 bit photo) the basic math would indicate that a printer has to lay down a grid of 16x16 dots per pixel in the photo and so to print a 300 PPI photo the required printer resolution would be 2400 DPI. That's a simplified description but basically that's what's going on.

billy_bones said:
2. could someone please explain the horizontal and vertical combination i.e. 600 x 300 DPI, surely it should print at the same quality in both the horizontal and the vertical? I'm either going onto the twilight zone here or am missing something that's probably obvious.

The higher of the two figures is interpolated. Interpolation means educated guess with an emphasis on the term guess. There is a real advantage to the 2nd higher figure but it certainly doesn't mean a 600 x 300 DPI printer prints at 600 DPI. Think of the print head moving back and forth over the paper. In that horizontal axis it may be able to produce 300 dots per inch. You would logically think that in the next pass over the paper the print head moves down the width of a dot, but it doesn't so that in the vertical pass there's overlap.

billy_bones said:
3. My old printer is a Canon Pixma MP160 with 4800 x 1200 DPI it is getting a bit old now (hence the search for a new one) but it has problems giving a decent print higher than a 6 x 4 photograph and that's on the best quality setting, using good paper and after going through the expensive rigmarole of cleaning the heads. saying this it is an inkjet printer can I expect better results from a laser printer? either with a lower, similar or higher DPI?

No. You'll get worse results from a laser printer. Laser printers have come a long way, but still have one critical flaw when it comes to printing photos. They can't hold a smooth continuous tone transition through the highlights to white. If you're after high quality photo output you're looking for a newer inkjet printer or consider using a printing service. Laser isn't the answer for photo quality.

Joe

billy_bones said:
4. I have my camera set on "large" picture size. would choosing a smaller size have any difference on the print result?

and finally
5. just info people might need rather than a question really . . .
I use a Nikon D5100 set to best quality and large picture (as stated) total 16.9 million pixels / effective 16.2 million pixels (not sure what that difference is for but that's the spec’s.) I am looking to print some exceptionally good quality prints at 10 x 8 (more or less A4) pictures are at 300dpi what should I be looking at for the spec’s in a laser printer please?

any help would be appreciated
thanks B.B.

KmH · Aug 30, 2013

DPI and PPI Explained - Andrew Dacey Photography

Image resolution is the pixel dimensions.
Print resolution is the pixels dimensions PLUS the pixels per inch value.
3000 x 2000 pixels @ 100 ppi will be a print that is 30" x 20". 3000 px / 100 ppi = 30 inches (pixel units cancel)
3000 x 2000 px at 300 ppi will be a print that is 10" x 6.67". 3000 px / 300 ppi = 10 inches (pixel units cancel)

Your D5100 takes are not 300 ppi. The camera assigns a value of 300 ppi to the image file.
Canon cameras assign a value of 72 ppi.
Using image editing software you can assign just about any ppi value you want.

With your D5100's Image Size set to Large the pixel dimensions (image resolution) of the images made are 4928 x 3264 pixels.
4928 px times 3264 px = 16.085 MP. (16.1 MP)

Part of the difference between 16.9 MP and the 'effective' 16.2 MP are rows of pixels on the image sensor that have opaque covers. Those covered pixels are used for assessing 'dark current', which is extra light outside the spectrum humans can see but that the image sensor can 'see'.
The “dark current” measurement defines a level beyond which image data becomes unsure. In the vocabulary of signal processing this is known as the noise floor.
http://wwwimages.adobe.com/www.adob...ly/prophotographer/pdfs/pscs3_renderprint.pdf

If you want a more complete source of information about printers and making photographic prints I highly recommend the recently published and inexpensive book:
The Digital Print: Preparing Images in Lightroom and Photoshop for Printing

http://printscan.about.com/od/printerscannerspecs/a/printerres.htm
http://desktoppub.about.com/cs/intermediate/a/measure_dpi.htm