resizing pictures without losing details

The PPI setting on a JPG coming out of a camera makes zero difference when it comes to quality. 72, 300, 1,000,000...it doesn't matter at all. These days, most cameras default to 300 PPI because that is widely considered to be a "good" resolution for printing, in that it will appear clear and sharp with pixels that aren't obvious. I think only old Canon DSLRs default to 72 PPI, and I am not sure why. Perhaps because in the old days displays like monitors were at 72 DPI? I have no idea.

But in the end, you are right about the fact that the only thing that matters is how many pixels there are. A digital image is nothing more than a huge sheet of graph paper. A pixel is like one of the boxes on that graph paper, filled in with a specific color. And the PPI setting simply tells you how many boxes there are per inch on the graph paper when you print it out. It doesn't create data. It doesn't affect how your image looks on a screen. Just how it looks when printed out.

thanks alot every 1 for clearing this out..and thanks you very much for your patience

Tha addiction all starts somewhere.

tytons wrote in post #6543291
thanks alot every 1 for clearing this out..and thanks you very much for your patience

OK, are you understanding? The dpi has nothing to do with image capture or IQ when you're viewing the image on-screen, right? The value is just there as a placeholder in your Exif and won't affect your image.

The only use for the value is when you are preparing to print and may need to resize, typically quite large.

Some stock agencies require resizing/resampling of images, by the way, to sell to publishers who require sizeable images.

When, by the way, you view an image at 100%, you are viewing the image at the native resolution of your graphics system, which varies with monitor and graphics card. My two monitors both resolve at 96 "dpi" so at 100% I'm displaying an image at 96 ppi. If I view at 50%, the monitor will still display at 96 dpi but I will be viewing the image compressed by 50% (2 pixels per dot), so I will see half of the fine detail but more of the image. This is why your software has you do adjustments to noise reduction and sharpening at a 100% view -- you are seeing all the detail in the image.

I'm going to use that line, next time I change my footer.

canonloader wrote in post #6547060
I'm going to use that line, next time I change my footer.

I relinquish my copyright of that phrase. That is of course unless you somehow make $1,000,000 off that phrase. Then I’m-a-gonna want my cut.

If I can make that much off that phrase, I will share it with you.

Good thread...........educa​tional..........and free- thanks.

tonylong wrote in post #6543979
OK, are you understanding? The dpi has nothing to do with image capture or IQ when you're viewing the image on-screen, right? The value is just there as a placeholder in your Exif and won't affect your image.

The only use for the value is when you are preparing to print and may need to resize, typically quite large.

Some stock agencies require resizing/resampling of images, by the way, to sell to publishers who require sizeable images.

When, by the way, you view an image at 100%, you are viewing the image at the native resolution of your graphics system, which varies with monitor and graphics card. My two monitors both resolve at 96 "dpi" so at 100% I'm displaying an image at 96 ppi. If I view at 50%, the monitor will still display at 96 dpi but I will be viewing the image compressed by 50% (2 pixels per dot), so I will see half of the fine detail but more of the image. This is why your software has you do adjustments to noise reduction and sharpening at a 100% view -- you are seeing all the detail in the image.

yea i guess im understanding,

i did some experiment where i resize my pictures to 72ppi and 300ppi. theres some difference in it..i think..or atleast thats what my eyes tells me.

so basically from now on if my pics are 72DPI ill just stick to it..and wont be adding more dpi to it unless i need to print.

but what im confuse about here is when i change the ppi in photoshop the default resolution changes..which makes sense. but when i change back the resolution to what i wanted..the picture would not turn out right.

any 1 here uses lightroom?any idea how to export pictures in the best quality in lightroom?as well as resizing them while exporting.

theres "bicubic sharper" in photoshop..how bout lightroom?

tytons wrote in post #6578084
yea i guess im understanding,

i did some experiment where i resize my pictures to 72ppi and 300ppi. theres some difference in it..i think..or atleast thats what my eyes tells me.

so basically from now on if my pics are 72DPI ill just stick to it..and wont be adding more dpi to it unless i need to print.

but what im confuse about here is when i change the ppi in photoshop the default resolution changes..which makes sense. but when i change back the resolution to what i wanted..the picture would not turn out right.

There is no point in changing the dpi/ppi in Photoshop unless you actually need to, as in you have a print lab that for some reason requires it.

In the Image Size window, if you want to experiment, deselect the Resample option, or else your resizing will either add pixels or take them away. Only have the Resample option selected when you want to produce a final image for, say, printing at 300 dpi.

If you want to resize for, say, Web display, you would want to change the pixel dimensions, not the ppi (the Web browsers use the monitor ppi to render the display). So, resize an image to, say, 800x600 pixels with Resample selected, then sharpen it, ignore the dpi figure, and you will have a picture optimized for the Web.

I do most of my developing and jpeg conversions in Lightroom (I still use 1.4). For the majority of my stuff I just use Lightroom sharpening and then save it to a Web-size jpeg and it's sufficient for "generic" Web use.

Lightroom 2 has an output sharpening function that should be useful for exporting jpegs, but since I'm still on 1.4 I can't comment on it. I have no idea how it compares to Photoshop's resize sharpening function.

Lightroom also has an output sharpening function for printing, which I do use and it seems to work well.

When you save a jpeg in Photoshop or export a jpeg for Web use from Lightroom, you have to take into consideration both pixel dimensions and file size. So, I give my jpegs a maximum height and width, and I set my quality to 75 (in Lightroom) to make for a smaller file size that can go into my PBase gallery and that will fit in a forum like this.

tonylong wrote in post #6578282
There is no point in changing the dpi/ppi in Photoshop unless you actually need to, as in you have a print lab that for some reason requires it.

In the Image Size window, if you want to experiment, deselect the Resample option, or else your resizing will either add pixels or take them away. Only have the Resample option selected when you want to produce a final image for, say, printing at 300 dpi.

If you want to resize for, say, Web display, you would want to change the pixel dimensions, not the ppi (the Web browsers use the monitor ppi to render the display). So, resize an image to, say, 800x600 pixels with Resample selected, then sharpen it, ignore the dpi figure, and you will have a picture optimized for the Web.

thats the answer i was searching for...finally knew why my pics turn out like crap when i played around with the ppi.

im using 1.4 as well, but i still find the exported image at quality 100 not as good as thoe that i resize on photoshop with "bicubic sharper" selecter. i upload my pics in flickr and they seem to load fine even with quality 12 on photoshop.i would assume its not too heavy for the web.

oh yea.i dont save as for web, but i use the "save as.."

This really is a great thread and is deserves to go in the FAQ section.