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jthsmak
03-06-2002, 10:21 AM
My bro does graphic design for our home business. He primarily uses photoshop. He is good at this, but studied painting, not design. Whenever he creates a new file, he insists on using a resolution of 600-700 pixels/inch. This creates files up to 150 mb big. Obviously, it is difficult to print these or even use my computer while it is printing or even open (Dual AMD AthlonXP 1.54 ghz, 512 mb DDR). I try to tell him this setting is unrealistic but i need proof that increasing the value to this degree does not improve image quality. I mean, these files are as big as videos. So, who is right? Also, what does this setting actually affect (other than file size). What is a good value for 8.5/11 prints mostly at 720 dpi? Thanks.

rsalonen
03-07-2002, 08:05 PM
umm, when I work in Photoshop I always start of by making the picture size 2 or 3 times bigger than I want the end resault to be. I can get more details that way.
but 150 MB for a 600 pixel pic? now how many hundred layers is used for that :p
My pictures is around 30 MB at maximum.

disdain
03-08-2002, 01:14 AM
I might be a little confused on exaclty what you are asking however ...

Any images I create that need to be printed I always use at least 600 pixels/inch. This produces a higher quality image that the printer needs to produce good results. If you were doing images that would only be displayed on the screen you could use a setting of 72 pixels/inch.

The more pixels - the better print quality.

- dis

studiomiguel
03-08-2002, 05:35 AM
I work in a very high end retouching shop with PSD everyday. EVERYTHING we do is at 304.8 ppi which is the international standard. Given, this is at 100%. Occasionally we will get a request to work something at half size and we will double the resoution or at double size and we will halve the resolution. These are very special circumstances though for highly specific applications (i.e. billboards or backlit displays). 98% of the time you will want to determine your final final final (this means the largest size you will ever use it for) size you need your image at and make it that dimension at 304.8 (300 ppi is fine). Creating a file at 10x10 inches at 1000ppi won't look any better than a 10x10 file created at 304.8 EVER.

rendermonkey23
03-08-2002, 07:00 AM
Well, Just remember that you can always sample down... but neverup. So if your positive (keyword) your only gonna use it for a website... then just make it at 72. If your ever going to print it then you have to know how big the very biggest it will ever be printed, then make it that size and the apropriate dpi (300, 600, etc...).

If he's working on the web mostly, 600 dpi is pointless.

theguy
03-19-2002, 02:25 AM
...it is a good idea to make it 2-4 times larger then you want the final outcome..but anything over 300 dpi is a waste of time if your still making it large..and has the system handles it..a lower dpi and larger image puts less stress on most systems with 384 or higher ram....but the smart fellow works on the simple system of 8... so if your standard dpi is 72 and you want higher uqlaity try 144 or 288 ...not a mentally pleasing number like 200 or 300 ...me and shea mccombs being as we are the few logical artists who apply experience to commen sense...tend to go with the larger image at 144dpi do not break the rule of 6 though..if its 6 times larger then the outcome there will be too much detail...or if you do insist on breaking the rule of 6 you must think of it in the sense of the old glass paintings like the huge ones you would see in movies like dune ...just massive...you have to work larger then normal cause your detail will look like dirt when you size down ...

Latuman
03-30-2002, 10:20 PM
I made the mistake to scan an image with 1200 resolution, and it... "Took all the juice" out of my 256MB 500MHz P3 (at that time). The resulting filesize was... Perhaps something about 600MB? Anyway that was just sick. First thing to do was to change it around 100, and then work with it and reduce it to 72 for desktop use. Thats why good scanners are for. At resolution of 75 should present a Moireless image. (My scanner was a cheap junk. Broke down recently.. :(

dave_baer
04-04-2002, 01:42 PM
The larger the resolution, the higher the image quality, thusly resulting in a greater file size. A larger resoltuion means you'll have more pixels per inch in which to hold information. It's good for photoretouching where you need to be exact and subtle. The higher resolution will make blending easier and less noticeable. Here's a few guidelines that I learned when creating images in Photoshop.

1) WEB - 72 dpi - You don't need any greater resolution since that's about the average size for an image being used for the web. Anything bigger makes for longer download times. Painting at a higher resolution, such as 300dpi, is okay to get detail but you'll need to convert it to 72 dpi for web use.

2) PRINT - 300 - 600 dpi - A very good resolution for high quality prints. Depending on the printer being used, if you're printing solid, flat colors with few blends, you probably won't even need to go this high. But if you are printing detailed photos or paintings, then vary the resolutions to your needs.

3) PHOTOSHOP PAINTING - I use 300 dpi to paint in and afterwords I convert it to 72 dpi for web use. 300 dpi lets me get detailed with very little loss after the conversion to 72. I don't really need anything higher as my images don't require anything more than that. I've seen matte painters who use 3000 - 5000 dpi. But their work requires them to be precise and highly detailed. However, unless you're running one hell of a PC, just opening an image like that could hang your machine. :cool:

FBMachine
04-11-2002, 09:14 AM
I really don't think I understand the pixels/inch resolution thing completely... I mean, if you're working on a 720x480 sized painting, there is going to be 720 pixels across, and 480 pixels down, whether the pixels per inch is set at 3, or 300, correct? Doesn't it only come into play when you're printing? Ie., for an image at 300 ppi that's getting printed out, every 300 pixels represents one inch of the printed page. So I don't understand the statement:
"300 dpi lets me get detailed with very little loss after the conversion to 72"
There shouldn't be any loss of detail on the screen unless you change the actual image resolution, right? I don't see how the ppi comes into it at all. It only makes sense to me when I know, say, something is going to be printed at 300 ppi, and it's going to be 8" x 10", so I have to work at least at 2400 x 3000. If I'm missing something, let me know, because it took me a while to understand even this much, so if I'm wrong, I'll be pissed :)
Dan

studiomiguel
04-11-2002, 10:16 AM
Your screen is 72 ppi. It can never display more than that. Regardless of the resolution of the image. The thing is that your computer will will store more detail in the image as the resolution rises. This allows your software to display more information as you zoom in on an image. That's why low rez images look bad when you zoom in on them. There is only so much data for the computer retrieve.

FBMachine
04-11-2002, 10:26 AM
Well what I'm saying is, if your monitor is set at 1280x1024, and you're looking at a 1280x1024 image full screen, zooming in on it will look just as ugly whether the ppi is 5, or 800,000. I've thought about it more, and it really is only for print. If the output is going to be digital, ei. not print, dpi/ppi is meaningless. Go open up photoshop and see for yourself. Just go by the image resolution. As far as dpi goes for printing, it depends on the output size and the material. For instance, I worked at a screen printing company, and the average dpi of the film we ran out for a half tone image was ~1200dpi if I recall correctly. So back to the original question, 600ppi isn't so outragous, it's possible he needs to print at that to get a good enough output for what he's doing.
Dan

FBMachine
04-11-2002, 10:29 AM
Think I used ppi and dpi interchangably enough? :)
Dan

dave_baer
04-12-2002, 11:20 AM
Well it all depends on what resolution the image was made at or converted to. If you made an image at 800,000 ppi (don't I wish) and u zoomed in on a detail area, you're going to see more detail in that spot than you would at 5 ppi. Just because your monitor is set at 1024x768 doesn't mean that the image you open is made at the same resolution. When u zoom in on an image made at a lower ppi, of course it's still going to look bad when u zoom in on it no matter what high resolution you are set at.

Is that what you were getting at?

FBMachine
04-12-2002, 01:04 PM
Ok, let's look at a typical image file... Let's say it's 32 bit ( 8 bits each for RGBA ). When a graphics application loads that image in to display, it looks at the resolution in the header of the file. Let's say the resolution is 512x512. The image file will be layed out linearly, so the graphics program will first read in the first 512 DWORD's. A DWORD is 4 bytes, one byte = 8 bits, so a DWORD is 32 bits. Those 512 DWORD's equal the top line of pixels in the image, 512 pixels. Then it will read in the next 512 DWORD's which will be the second line of pixels in the image. I know went a bit far with the technical crap, but notice that no where in there have I said anything about ppi.. 512x512 is 512 pixels across, by 512 pixels down. There is no hidden data in there that will somehow hold more detail if the ppi is set higher. That's why a 512x512 800ppi file will be the same size as a 512x512 8ppi file. Ppi is mearly a scale that is used during print time to determine how much space each pixel will take up on the printed page. Screen resolution has nothing to do with this, my mention of it in my last post was misinterpreted, I didn't really explain myself well.
Dan

FBMachine
04-12-2002, 01:09 PM
"That's why a 512x512 800ppi file will be the same size as a 512x512 8ppi file."
What I meant there was the size of the file on the harddrive, not the size of the images printed, which would be different...
Dan

FBMachine
04-12-2002, 01:13 PM
Oh, and in case any graphics programming nerds frequent this forum, I know my stating that the first 512 DWORD's corresponds to the top line of pixels in the image is kind of misleading, some formats start from the bottom line up. :)
Dan

FBMachine
04-12-2002, 01:24 PM
Ok, I just came up with a way to show you a little proof behind what I'm saying in case you think I'm nuts or something. :) Open up photoshop and go to create a new file. In the new file dialog, set the width and height to be set as "inches" in the drop down lists. Now flip back and forth between 300 and 30 under Resolution pixels/inch. Watch the file size fluctuate up and down under "Image Size:". Now set the width and height to be set as pixels. Now flip back and forth between 300 and 30 under Resolution pixels/inch. Notice how the file size doesn't change now. 1024x1024 is 1024 across by 1024 down, no matter what the ppi, no matter what your monitors resolution is set at. Ppi is only a scale used when printing.
Dan

Gilgamesh
04-12-2002, 04:17 PM
I understand most of that stuff, but I was wondering if someone could clear this up:

Isn't the ppi on screen going to be different with different screen sizes and resolutions? I know that 72 ppi is standard, but it seems logical that if I raise the resolution on screen, then there are going to more pixels squeezed into the inch. So does that mean that a screen inch is relative, and doesn't actually correspond to a ruler if I were to stick it up to my monitor?

windowlicker
04-12-2002, 07:58 PM
Gilgamesh: The screen-size is something rather different... All dpi (ppi) does is define the resolution in print.

On screen the inch is relative.
Example: My monitor is approximately 30 cm (11.8 inches) wide and running at 1280x1024 resolution. 11.8inches/1280px means every pixel is 0.00922 inches wide. Multiply that value with 72 to get the "relative inch" (0.00953x72=0.686). This should state that 1 "screen inch" equals 0.664 real inches. (Hope I got i right!) ;)
Test this by using the rulers in Photoshop.... which I just did, and for some reason it doesn't seem to be right!! :shrug: Oh well...

For screen-use however, just go with the pixel-width/height of the image, never mind the resolution unless you want it in print. :)

_a_
04-15-2002, 12:38 AM
Holy crap! that's the most confusing series of questions/answers/statements I've ever heard! It's really not as confusing as you all make it out to be (at least i think so, i'm not sure after reading all that malarky! lol) I think you were measuring your entire screen size, not the projected screen size. You would need to adjust your screen to be an exact width across to get an acurate measurement for the equation. I tried doing it, but it's really really REALLY hard trying to measure the screen with a ruler, as I'm sure you know. Didnt really have anything to add, just thought i'd continue with confusing people who read this. :eek:

jman
05-02-2002, 12:33 AM
Yeah FBMachine is absolutly right.

And I worked in the print businness for 3 years, and you have to determine the kind of paper you are gonna print on.

If it's a good quality paper, you can print something that have a 300dpi of resolution.

Newspaper journal up to 150 dpi.

The DPI use is usualy twice the screen ruling.

ANd the screen rulling is determine by the type of paper.
Ask your printer about the screen ruling

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