Is it true that 300 ppi is the limit of sharpness that the human eye can see?

Question

In other words, what's so special about that very popular figure?

Answer 1

300 dpi (dots per inch) is the standard quality to produce a good, clean, sharp photographic quality print. Any online photo printing site will suggest this as the best quality, although a little less can still make extremely good photographs.

If printing at home, only the very best printers can print at 300 dpi efficiently, most will produce better pictures at about 240 dpi. The reason for this is that the average good personal printer can lay ink down in a dot, with 240 dots in every inch with clarity. If it is not a top end printer and you try to print with 300 dots in every inch the ink dots tend to blur a little together, thus producing a slightly less sharp image.

The amount of dpi that an image should be saved at it wholly dependent on what you wish to do with the picture. If it is purely to be seen online, then 72dpi is all that you need. This is how all screen resolutions will view the picture and so a picture of 300 dpi will look no better on a screen than one of 72 dpi.

If you wish to make a very large print by simply enlarging the image, the best quality is achieved by having 300 dpi after the enlargement. Photo Shop is the easiest software to use for enlarging and keeping your dpi levels up.

Answer 2

If you are referring to PRINT media, that's about right. Okay, you can magnify and see the dots, but don't torture yourself. However... It is always nice to have a printer that will exceed the goal of 300 dpi and ESSENTIAL to have a scanner and camera that will do much, much better than that. It is so much easier to work with larger files before printing them.

Now, I can see some confusion coming in, so I would like to re-post a discussion I wrote a while ago on a related topic. Just don't forget that you are looking at 300 dpi as a goal for prints.

Resolution - PPI - DPI

You can not control the pixels per inch in your camera, as this is a function of the sensor. I have found the following ppi for SOME cameras by the following manufacturers. I wonder if this specification is available anywhere. I have four camera manuals in front of me and I can't find it in any of them.

NIKON - 300 ppi
CANON - 180 ppi
PENTAX - 72 ppi

We "discussed" this by way of question and answers a while back and decided that the ppi file produced by the camera really did not have any effect on the capability to produce a good print. If I take a photo with my wife's 6 MP Nikon and view the image on the screen, it will start out as 300 ppi. If it's a full frame image of 3008 pixels x 2000 pixels, the SCREEN image would be pretty big if I viewed it full sized, but it would print 10.0" x 6.6". If you crop a 5x7 out of this, keeping it as full-frame as possible, it becomes 400 dpi.

With my brother's 6 MP Pentax, the image is 2816 px x 2112 px, but it's at 72 ppi.

If you print this without cropping, it would be 39" x 29"!!! If you crop a 5x7 out of this, though, it becomes 402 dpi resolution, which is virtually identical for the Nikon 6 MP camera.

With my son's 6 MP Canon Powershot A620, the image is 3072 px x 2304 px, but it's at 180 ppi. If you could possibly print this without cropping, it would be 17.1" x 12.8". If you crop a 5x7 out of this, though, it becomes 439 dpi resolution, which is a bit better than either of the other 6 MP cameras.

In other words, regardless of the sensor's pixel-per-inch output, 6 MP cameras produced the same resolution when it came time to print comparable images. How about a camera with more pixels?

If I take a photo with my 10 MP Nikon D200 and view the image on the screen, it will start out as 300 ppi. If it's a full frame image of 3872 pixels x 2592 pixels, the SCREEN image would be pretty big if I viewed it full sized, but it would print 12.9" x 8.6", if I had the right paper. If you crop a 5x7 out of this, keeping it as full-frame as possible, it becomes 516 dpi, or higher resolution than the 6 MP cameras. We knew that is would work out like this, though, didn't we?

The REAL question is, what difference does this make in the real world? If we agree that 300 dpi is an excellent resolution for prints, as long as you end up with at least 300 ppi after you are done cropping on the screen, you will get an excellent print as far as resolution goes. All four cameras exceed that amount. I usually resize "down" to 300 dpi before printing, because you can't tell the difference above that resolution anyway. Most people would be quite happy with a 200 dpi print, so go ahead and crop a bit. If you get a print resolution too much below 200 dpi, you will start to see digital artifact in the print and it will be objectionable.

Answer 3

see some people look at teeth while other look at eyes or lips. To me it's the whole face. I look at the face as a whole. So no for me thats not true. I have seen guys with eyes that are to die for, but I still don't find them attractive. Personality defines looks to me.

Answer 4

Not that I've heard. the eye has roughly 100 million rods, which also have the ability to sense intensity, so depending on how close you bring an object to your field of vision would determine what resolution it would have to you.

Answer 5

sounds like someone was trying to sell you ? a cheep camera, video cam or print?