Forum: Photography


Subject: Image size?

Javafoto opened this issue on Jan 05, 2004 ยท 14 posts


Javafoto posted Mon, 05 January 2004 at 10:31 PM

I know the 512 limitation on image size, but is there a prefered or optimized image size for posting on this site? i.e.> x number of pixels, etc. It seems to take me forever to down size my images. Thanks,Michael


PunkClown posted Mon, 05 January 2004 at 11:47 PM

PunkHead.jpg72 dpi is the best resolution the human eye will be able to resolve from most monitors, so any larger dpi setting is wasted for posting on the web. A lot of people have 17" or larger monitors set to 1024 X 768 resolution, but there are always a few who haven't. I usually restrict the width of my images to 800px and try and limit height to 600px to minimize scrolling that online viewers would have to do (providing of course, that anyone actually views any of my stuff chuckle)
What program(s) are you using? Photoshop has the "save for the web" option that gives you a fair degree of control over minimising your file sizes for upload, where you can balance optimised/smaller file sizes against the inevitable jpg artifacting and loss of detail that occurs with a great deal of image compression. I hope this helps...umm, what was the question again?


DHolman posted Tue, 06 January 2004 at 4:19 AM

I agree with PC on everything but the first sentence. It's one of my pet peeves. The 72dpi standard is a fantasy; a hold over from the early days of computers that no longer means anything. For monitors, ignore dpi and stick strictly with the resolution. It amazes me how many reputable computer magazines and sites continue to prescribe this as a standard. For me, I usually think of the standard resolution for today's systems as being 1024x768 (I run 1280x1024 on my screen). I usually make the largest dimension on a photo 668 pixels when I resize it. Once I add my border, it becomes 700 pixels. -=>Donald


Michelle A. posted Tue, 06 January 2004 at 5:33 AM

If you keep the image under 200k.... chances are more people will look at it.... Some people are still on dial-up, and will skip over huge file sizes.... I'm on a cable connection and I tend to ignore the big ones too. There is really no reason why any image should be that large. I post at under 800X600 and keep my images to well under 200k, no one has complained yet that they look too compressed, and they shouldn't.

I am, therefore I create.......
--- michelleamarante.com


PunkClown posted Tue, 06 January 2004 at 5:42 AM

But Donald, the more dpi in an image, the larger the file size. I am willing to accept all that you say about screens and dpi, but when it comes to upoading images their file size does influence uipload time (and I'm on dial-up so it makes a biog differnce to me when browsing the galleries) ~ btw, curious minds wish to know, on which monitors can you tell the differences between an image at 100dpi and 300dpi (as an example) ~ because I want one! (grumbling ...it'll probably be one of those MacIntosh huge LCD screens, I suppose - not compatible with my system or budget! LOL) :-)>


DHolman posted Tue, 06 January 2004 at 6:44 AM

Cam: The reason DPI is meaningless on a monitor is that DPI is a standard output. Taken to its simplest form, it means the number of dots that lined up one after another measures one inch of output. This works on output devices like printers. No matter the brand or size of the printer (whether it's a little 4"x6" inkjet photo printer or a HP designjet capable of 53" wide output) if you print 72 pixels in a straight line at 72dpi, you get a 1" long line [within mechanical tolerance of course]. Now, think of a monitor. You've got Joe sitting there with a nice 800x600 screen on a 19" monitor. He has 72 pixels lined up across his screen at 72dpi and miracle of miracles, it measures 1". Now Joe doesn't touch the image, but changes his screen resolution to 1280x1024. Now, his 72 pixel line in the 72dpi image that he hasn't touched measures only about 0.6" in length. Joe puts the desktop res back to 800x600, but changes from the 19" monitor to a 17" monitor or to a 21" monitor. The length of the line changes proportionally with the size of the monitor. In fact, the line length will change with every monitor and screen resolution change. So, in essence, since there is no one "standard monitor size and screen resolution" you can't apply a standard like DPI to it. File resolution alone is independent of DPI; DPI is a standard for output. The reason an image gets larger when you change its DPI in a program like Photoshop is because you are telling it to resample (enlarge or decrease) relative to the old DPI. So, if you have a 1000x1000 image at 100DPI and you tell it to go to 200DPI with resampling, Photoshop says "The user wants to print the image the same size as before, but they want to do it with twice as many pixels making up one inch, so I must increase the resolution by twice as much" and the image becomes 2000x2000. Here's a good visual, load an image in photoshop. Go to "Image Size", uncheck "Resample Image" and then change the DPI. Notice how the resolution stays the same, but as you increase the DPI the printed size goes down, and as you decrease it the size goes up - even though resolution remained the same. Next two images are examples of what I mean. -=>Donald


DHolman posted Tue, 06 January 2004 at 6:45 AM

This image was set to 72dpi and saved (resampling off).

DHolman posted Tue, 06 January 2004 at 6:56 AM

This one was set to 1 (one) DPI and saved. See any difference? For web/monitor output, it's not the DPI that sets the size ... it's the resolution. You can use the DPI setting to do your resizing, but it's not as precise. If I bring my photos in from my EOS 10D at 300dpi and resample them to 72dpi they go from 3076x2052 to 738x492. However someone with a ~4megapixel camera doing the same thing would go from a 2272x1704 image to 545x409. It's that whole non-standard standard thing rearing its head. Sorry if that was long winded ... like I said, it's a pet peeve of mine. Drives me crazy for some reason. -=>Donald

MrMichael posted Tue, 06 January 2004 at 9:52 AM

I only consider DPI when I desire to print something, it seems to be the only time it matters. As for my posts: I usually give 1280x853 200k (max) images. I don't think I've heard any complaints, but are there any of you our there that think I should drop that size down?


Tedz posted Tue, 06 January 2004 at 9:23 PM

I don't know what DPI is.....but for all My Personel Shots...I even have to use a Macro to make things look Big ...I'm not quite sure what You are all talking about...size does not count in matters of Luuuuuuuuuuuuurve!


Wolfsnap posted Tue, 06 January 2004 at 11:10 PM

I sat here for a bit trying to understand what you were explaining - and then it hit me - and you're dead right! the monitor resolution determines how the image is going to be displayed (a 4x6 image at 200 DPI is going to look the same as an 8 x 12 at 100 dpi - they're both 800 x 1200 pixels) - and the monitor, pretty much set at a "72 dpi setting" will resize the image to look the same in either case...?


JordyArt posted Wed, 07 January 2004 at 2:32 PM

sigh I don't get involved in these petty squabbles. No matter what anyone says, size matters. The only people that say it doesn't are the ones who have something to hide. oh, and no matter how big it is on screen, it always looks bigger in the mirror ;) (",)


PunkClown posted Wed, 07 January 2004 at 5:39 PM

PunkHead.jpgThanks Donald, your explanation does make sense (when I digested what you said and thought about it...lol, the gears were grinding a bit) Oh, Jordy...I've often found that the ones that have to boast about size are often those that have some short comings in that department! ;-)>


DHolman posted Fri, 09 January 2004 at 12:56 AM

PC - It's one of those things that easy for me to think of, but a pain in the butt to try and explain. Wolf - Ummm, almost. Monitors aren't set at 72dpi. There is no standard monitor DPI; that's the point. If you don't have a standard monitor resolution and size, you can't have a standard that describes how it will look on the screen. Easiest way to think about it is, if it's going to a monitor screen then you worry about the resolution; the DPI setting will have no bearing. When you output to a printer, you need to worry about resolution and DPI. -=>Donald