confused about Resolution size

[Tendy]

right, normally if its a pic for the web I'll resize it to 800 by whatever, 72 ppi is sufficient as its not gonna be printed.
However, I have some pics on deviantArt.com that are much bigger and available as prints. Only thing is if I want to resize it just a little I have to untick the default 72ppi setting in PS elements 1 and select 200 or 300. (I untick 'Resample' first then go back in and resize to whatever size i want.)
Thing is when I choose 300 ppi the print size goes down to something like 5 x 3.5 inches! So I go down to 200 ppi and get a bigger print possibility. But arent I losing quality by selecting a lower ppi?
I'm confused!!

[tracknut]

You are confused :)

Think of it this way. You've got an image, let's say it's 800x1000 pixels. Without resampling, at 72ppi ("take each block of 72 pixels square and make that one inch on the paper") you'll have a print of 11.1" x 13.9" (800/72 by 1000/72). At 1ppi, you'd have a print of 800" by 1000", and at 800ppi, you'd have a print of 1" x 1.25". In other words, if you don't resample the image, you're using the exact same 800x1000 pixels to make each of these images, you're just printing them at different sizes on your printer. I would not call any of these "lower quality" than the other, as they're all printing the exact same 800x1000 pixels.

On the other hand if you resample, then the question of "losing quality" is probably relevant. If you resample *downwards* you are throwing away pixels, and if you resample *upwards* you are inventing pixels where they didn't exist before. In both of those cases you could argue that this represents a change in quality from the original 800x1000 image.

Make sense?

Dave

[Tendy]

Err i think so. Its just that when i open the resize box its set to 72 ppi by default. Thats screen resolution,not good enough for printing right? Or do I untick the resample box and set the resize rate myself,in pixels?

[tracknut]

It's set to 72ppi most likely because that's what your camera set it to.

Personally I have PS resample, for my prints. I suspect it does a better job at it than the printer driver, but I've never done a test. So yes, let's say you want to turn that 800x1000 pixel jpg file into a print that's 8x10" at 300ppi. You'd keep the "resample" box checked, change the size to 8"x10", set the ppi to 300, and click OK. You'll be upsampling by a factor of 3 in each direction, since the original image has 100ppi as an 8x10" print.

Dave

[Tendy]

Oh man i should have posted this earlier while i had the laptop on(using my phone now)
Thing is no matter what camera I use the image size shows as 72. Now when i was scanning photos,before digital,I remember being advised to select as high a ppi as possible for max print quality-72 being the resolution of the computer screens then.

[tracknut]

Thing is no matter what camera I use the image size shows as 72. Now when i was scanning photos,before digital,I remember being advised to select as high a ppi as possible for max print quality-72 being the resolution of the computer screens then.

Doesn't really matter what your camera sticks in there. 72, 1000, 42... it's all just pixels, and your sensor spits out the same number of them regardless of your ppi setting. That's what I was (apparently poorly) describing in my first response. Yes, when you're scanning a photo, it makes sense to scan at as high a ppi as possible, but that's not what you're doing here.

Dave

[tkfoto]

You need to grasp what the "dpi" number is, isn't, and why you should usually not care.

In the case of your cropping...if you crop to 8x10 and have 72 pixels/inch shown in the crop settings (mine comes up blank by default...) what you're really saying is you want to take whatever portion of the image you crop, and set it to 576 x 720 pixels. If you crop a tiny area it's going to look like garbage because it's going to be massively upsampling inventing, as was said, pixels that weren't there.

On the other hand, if you take a maximum size crop with that 8x10 ratio, you're going to be throwing out a lot of pixels and your resulting resize won't be much good for printing (at least at the 8x10 size).

The "dpi" setting is a multiplier, pure and simple. You should remove it from your workflow and not resample based on it. Keep all the original pixels without inventing more or throwing away perfectly good ones. Then when you do print, you can tell it what size to print and end up with the best image possible.

I could put up a pair of images, one that would come up at 1 dpi in photoshop, and the other would come up at 30,000 dpi. I am 100% positive you would not know the difference. Because there would be none...except for that dpi stored away as a multiplier in the depths of the image.

[Tendy]

You mean ppi,not dpi,which relates to printers. The only thing with all this-and what got this started,was when i upload a pic to deviantart and select it as a print it often tells me its unable to select such and such a size,'ppi not met'

[Disassociation]

the easiest way to get good results, is to avoid resizing using photoshop altogether.

I have had prints done through deviantart as well in the past, with really good results. They actually do a very high quality job, its just also, VERY expensive (for me, over 2X the cost of costco or kodak locally).

The easiest way to approach it, is to edit the photo to your liking, without resizing. Then, upload the image to deviantart and tell it what resolution to show to people who look at the image. Since you have uploaded a much larger, higher resolution image, deviantart will recognize this when you go to print your image, and will allow you to choose much larger prints. Don't change the ppi/dpi settings, simply take them as they are from the camera.

I hope this helps :)

[Tendy]

Thanks Dan! Thing is i don't want to use dArt for printing myself,I put them up hoping others will buy them. I get the feeling that's not worth it tho!

[tkfoto]

You mean ppi,not dpi,which relates to printers. The only thing with all this-and what got this started,was when i upload a pic to deviantart and select it as a print it often tells me its unable to select such and such a size,'ppi not met'


If you mean me then yes, I am using the terms as if they were fully interchangeable, which I know they're not. But people keep using them that way, so I'm left trying to rip the confusion out any way possible.

It gets really confusing when you start talking about printers and how, say, a certain printer might print 1440dpi x 360 dpi or something.

Well, 1440 is 360 * 4... and said printer has CMYK ink tanks...thus *4.

Kinda like the new crop of cameras with "922,000 pixel" LCDs. Well, not quite. The resolution is 640x480 (307,200) but with RGB dots...*3...~921,000.

[Tendy]

Heres two exapmles to show what I'm talking about.
See the box set to 72ppi? And if its ticked I can change the pixel count:
http://img.photobucket.com/albums/v11/Dawnrider/ppi.jpg

but here you can see that if i untick the box, so as not to resample, i cant resize:
http://img.photobucket.com/albums/v11/Dawnrider/ppi02.jpg

[tkfoto]

OK, you're doing the right thing. Resizing by pixel count is _proper_. The problem comes from stupid requirements and workflow when you don't know better. And trust me I could quote things far more ignorant than the process/example I'm about to present...things that I've actually seen people do. Note the word ignorant is not an insult ( a lot of people seem to take it as such).

The problem comes in like this...I've had sites ask me to submit photos "1000px on the long side, at 72dpi".

I forget what my camera actually sets the DPI to in the file...like 140 or 190 or 240 or something...I don't pay enough attention to care. Let's assume it's 240.

So, if I don't know any better I might look at that requirement and say "OK, I need this photo at 72dpi. I'll do that first". So I go into that screen and change from 240 to 72 and hit OK. At that point, PS is going to downsample my file from 3072x2048 to 921x614. So now I go in and upsize it to meet their 1000px requirement. I've just gotten a lousy resample by throwing away good pixels and then trying to recreate them. And I've seen people _DO_ this because "that's what they were told to do".

The proper way would be to resize down to 1000px on long side and submit. However, I've actually had said site complain that "You sent me a file in 240dpi" (even though it was, as you correctly pointed out, ppi not dpi.

So I had to open the file, _un_ check "resample image", set it to 72ppi and resubmit and they were happy.

So to put it simply...check the resample box when you're changing pixel counts. Uncheck it when changing the PPI if someone has given you a stupid requirement for "DPI" and thinks it's the same thing.

[Tendy]

Another site I use has a requirenent for photos that are no more than 600 px on a side and less than 100K!(say 600 x 400 at <100K )
Hardly a great way to see photos at their best!