Do pixels matter? What 20" x 30" prints reveal.

Started Jun 14, 2013 | Discussions thread
MOD Mako2011 Forum Pro • Posts: 26,748
printer res

rwbaron wrote:

Mako2011 wrote:

rwbaron wrote:

bronxbombers4 wrote:

LaszloBencze wrote:

I currently have a show of 38 20" x 30" prints appearing at the Viewpoint Photographic Art Center in Sacramento. Most of the pictures were taken with either a 5D MKII or 5D MKIII. However, some of them come from the Canon 1D MKII and 1DMIII which are not full frame and have about half the number of pixels of the 5D cameras (8 & 10 megapixels vs over 20 for the 5Ds).

What I noticed is that I could not tell which pictures were taken with the lower pixel count 1D cameras. They do not stand out as obviously inferior. In fact all the pictures look good and are indistinguishable in terms of sharpness or resolution.

Now I'm sure that there are benefits of the 20 megapixel cameras. And I do own two of them. But my point is that real life photo situations with large areas of bland texture or out of focus areas do not reveal such differences. This is a bit of a surprise for me but a reassuring one.

If you happen to live in the Sacramento area, you're welcome to look for yourself. The gallery is at 2015 J street and is well identified with signage.

All I can say is could tell apart 8MP from 20MP prints even on an 8x11 never mind 20x30!

I printed at 720PPI on crisp paper.

Plus you have a lot more freedom to crop the 20MP images when you need to and they sure give a lot more reach for stuff like sports and especially wildlife.

I'm confident you have a lot more experience with this than I but why are you printing at 720PPI? I did a comparison on my Canon i9900 and could see little advantage going above 240 and in many cases 180. The commercial printer I work with who has the latest and biggest Epson and Canon printers has never asked for a file more than 240PPI. To print at 720 you have to upres the files dramatically even from a high res sensor which would cause all sorts of artifacts.


Apples and oranges. A 720 dpi printer produces ink blobs 1/720 inch apart, but they overlap. Your i9900 is actually doing that and more at the fine setting. It's how you get color fidelity from 8 inks. The 240 PPI, your commercial printer asks for, refers to the images resolution Pixels per inch. Most likely he is printing those pixels at a much higher dpi (drops of ink per inch). bronxbombers4 may be mixing his terms. PPI vs DPI
You probably cannot truly resolve more than 200 to 300 PPI on the picture,
depending on the kind of paper. Nonetheless the higher "resolution" DPI of the
printer helps give a smoother and more color accurate image.

Note...Printers need to dither, and their current
effective full-color resolution is around the 240-300ppi mark.
However, you should send the jobs at 720ppi (for Epson, 600ppi for
Canon) because this is the driver's native resolution and assuming you
have un-sharped the image, there will be high-contrast areas that the
printer may be able to achieve towards 720ppi. Question will be if you print will be large enough to notice the smooth high-contrast transition. Likely not.

Better explanation:

I know the difference and I'm talking about PPI not DPI.

I take a RAW file from my 7D and open it in PS at 240 PPI. The native image is 5184x3456 which equates to a 14.4x21.6 inch print and the file size is 102.5 meg as a Tiff. If I change the resolution to 720 and keep the print size the same the file becomes 922.6 meg. I've never printed anything at greater than 300 PPI and large prints typically at 240 and even less with excellent results. Maybe there's something I'm missing but what benefit is it to interpolate a file to that size for printing?

The printer has a native resolution as well. By sending it a file in the same native resolution, it can then dither the resulting print more accurately. Will only come into play where there are stark contrast/color transitions. When printing something very cam make a difference in the transitions if the printer driver is not re-sampling to get to its native 720 or 1440 dpi.

Better Explanation:


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My opinions are my own and not those of DPR or its administration. They carry no 'special' value (except to me and Lacie of course)

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