Resolution explanation

Irishman

Irishman

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This was sent to me by a customer, but can anyone please explain it to me in plain English, I have read this a number of time and still can't get my head around what they are saying?​
'A hi res image can come in various formats ranging from 90-180cm width at a resolution of 72 dpi, or 30cm and a resolution of 300dpi - a professional photographer will always know what is meant by it'​
 
Your customer is referring to print quality ie. ppi ( pixels per inch). The image resolution is what it is.

Your image can be printed at a high print quality of 300ppiwhich will be very high quality but at a smaller size or you could print it much larger at a lower ppi. The larger image won’t look great when viewed closeup but will look good from a distance ( think billboard ).
 
As many of us would know, dpi means dot per inch, thus 72dpi is 72 drops of ink in 1 inch wide, and 300 dpi is 300 dots in 1 inch wide. We all know that.

People would assume that because there is 300 drops of ink in the one inch width, therefore it must look so good to the naked eye, better than the 72 drops of ink in the same space. But here's the thing...

30cm is roughly just about almost 12 inches, so let us round it up to 12 inches. At a setting of 300dpi, it is 300 drops x 12 inches (30cm) = 3600 drops in 12 inches wide.

Now, about this 90-180cm, let us round it up to say 127cm, which is nearly just about 50 inches.

So at a setting of 72dpi, it is 72 drops x 50 inches (127cm) = 3600 drops in 50 inches wide.

Now you got one image 3600 drops of ink 12 inches wide and another image in 3600 drops of ink in 50 inches wide.

The point is...

At 300dpi, a 30cm image is just about almost an A4 paper landscape, so you would be holding it and looking at it, and you can see a great image.

At 72dpi, a 127cm image, that is a bit bigger than A0 paper (yes there is A0 size according to Wikipedia, and this is just 16 times bigger than A4), and if you hold it (we can hold a paper that's just about a little more than a metre wide, it's like holding a totally opened OS map), but you may be thinking, the image look bad because you can see dots of ink.

The only problem is that you are looking at a piece of the image. You need to turn your head around from side to side to look at the whole picture, so you may feel like wanting to stick it on the wall, take a lot of steps back, maybe on the other side of the room, and look at it within your field of vision, and what happens then? You are so far away you can see a clear image, but can't see the dots of ink.

To put it in plain English, and to use an analogy, it would (more or less) be like...

With a page torn out of a paperback novel. As a normal size adult, you can see all the words but can't see the dots of ink. But if you were to be shrunk to the size of a Barbie doll, and hold the same torn out page, you end up not able to read the words as you would be looking at few big letters within your field of version, but you would see those dots of ink, unless you put it on the wall and step back, then you can read all the words but can't see the dots.

Hope this is as plain English as I can offer?
 
They should either say what size it is going to be printed (and on what medium), or how many pixels they want.

Clients often mix everything up. Another one is giving them a file with the number of pixels they need and getting “this is too big”, when what they actually want is more jpg compression...
 
droj said:
Unnecessary obfuscation. All that matters are the pixel dimensions. Resolution in that context can be ignored.
Click to expand...
I think that's the point the customer is making.

ie. a 72DPI image can be considered high resolution (if it's wide or tall) just as much as a smaller 300dpi image. The second half of the quote indicating that anyone who knows their stuff knows this to be true.

I assume the original quote is in the context of a conversation - perhaps in response to 'No, I asked for hi-res, why did you send me a 72dpi image?'
 
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