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Input/Output/Workflow Scanning, printing, color management, and discussing best practices for control and repeatability

resolution quesion

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Old 10-26-2005, 08:32 AM
ydelle's Avatar
ydelle ydelle is offline
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resolution quesion

I would like to know why some pictures print great at 72-75 lines of resolution where other look bad.
I know my camera takes at the highest level 72 lines and the pics are 22x?
and then I make them smaller at 200 lines. Now here is the thing I posted a sunflower that I painted and as I was trying to size it for framing -noticed I had forgotten to change the 72size- it looks great. Others taken at the same time look jagged.
Is it just hit and miss?
My camera is 3x single lens panasonic DMC-LC20. I also get pics a work for customer and their pics are at 72 and print out just fine ?????
I have had my camera for about 2 years before that took film Minolta 35 with changable lens, but got tired of carrying it and having to wait for pics to be developed.
ps I have blow up some of my work to 11x14 with out loosing anything and some smaller ones look funky.
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Old 10-26-2005, 12:42 PM
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CathyH CathyH is offline
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This is a great question, I hope someone can answer it in simple english.

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Old 10-26-2005, 02:06 PM
cspringer cspringer is offline
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my 72ppi (Sony 717) would print at approx. 35x26 inches. What size are your prints? I'm guessing they are being converted at some point in the process.
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Old 10-26-2005, 02:31 PM
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Craig Walters Craig Walters is offline
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resolution in the digital world is measured in dpi, which means 'dots per inch'. and that's linear dots per inch, not number of dots per square inch. so, if you take one line and one inch of that line, how many dots are there in that one inch and that's your resolution.

however, it's actually just a tiny bit more than that, particularly when you're talking about monitor resolution. when specifically talking about monitors, it becomes how many dots per inch can you actually distinguish at a particular distance away from the screen.

it's also important to know that pixels are always squares or rectanglur, never circles or elipses of any sort.

but ok, let's just talk pictures. there are a number of factors in the apparencies of an image. some images may appear to be jagged when you get two colors side by side, particularly on a diagonal. this is usually called 'the jaggies'. they appear jagged and not well blended into each other. this will usually occur where the colors (or black and white) are highly contrasted to each other. black next to white is going to show the jaggies quite readily, where magenta and a red wont show up quite as badly. different colors contrast to each other this way where others may well not be as apparent.

the other thing that is done is a bit of a trick in the digital world. if you have two contrasting colors going diagonally next to each other, you can do what's called anti-aliasing. this is just a fancy term meaning to blend with an intermidiate color/hue/shade to make the jaggies sort of disappear. in other words, you're sort of making a transitional stage there to take one color slowly into another. this has nothing to do with changing resolutions. it's just a trick to fool the eye.

the other side of that same coin is called 'dithering'. again, this is just a fancy term for blending away the jaggies and is essentially the same thing as anti-aliasing only it's applied in a slightly different spot from anti-aliasing.

i'm enclosing a picture to help illustrate this. the green circle is circling an example of dithering. the wide blue line has jaggies. i smoothed this out by taking a blue brush color and smoothing along the blue.

the one with the red circle is the opposite, anti-aliasing. i did the same thing as the blue only on the outside of the blue on the white with a white color brush.

on the one circled in black, i did a sort of combo of both types.

for the most part, this has become one term, anti-aliasing. the term 'dithering' seems to be being dropped from use a lot. and usually the smoothing is done with intermiate colors. like if you were trying to remove the jaggies along white line, you might use different shades of white to fill in around the jaggies.

so, basically, some lower resolution cameras may be incorporating software that does this anti-aliasing automatically. and, the picture you are taking may not have severe enough contrasts to notice the jaggies that much. so, it's going to vary picture to picture.

now, i shld also warn you to look the terms up yourself. i'm fairly sure about anti-aliasing, but i may have dithering wrong. but, regardless, the idea is you're smoothing out the jaggies one way or another. thus, resolution isnt the only component for a good looking picture.

and, one last note on this. if you're looking at a picture in photoshop or some other paint program, how far or close you are zoomed in is going to make a difference in how things look. and, if you've resized a picture, that's going to change things also.


edit: ok, here's a 2nd example of what i'm talking about. this one might be easier to see. notice the transition of blue to white on the right side of the blue line and no transition on the left side.
Attached Images
File Type: jpg example-1-k-1.jpg (54.4 KB, 8 views)
File Type: jpg example2-1-k-1.jpg (36.8 KB, 2 views)

Last edited by Craig Walters; 10-26-2005 at 02:42 PM.
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Old 10-26-2005, 03:44 PM
ydelle's Avatar
ydelle ydelle is offline
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Thanks Craig, Now I hope more people want to discuss this. I just opened Photoshop and I did not see anti or dithering anywhere- is that something one has to do by hand?
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