Best Way to Reduce Resolution

I have about 200 hi-res photos that need to be changed to lo-res photos, i.e., from 300 dpi to 72 dpi. Nothing else needs to be changed. The image dimensions will remain the same, although the file size, of course, will be smaller.

I have PS CS3 and Bridge. Of the various ways to do this, which is most efficient? And since I will be doing more of this in the future, should I be thinking about Lightroom?

using Bridge and Photoshop,

select your images in Bridge and use image processor with an action to reduce the images using bicubic sharper

I don't use LR

The image dimensions will remain the same, although the file size, of course, will be smaller.

In fact, the file size will not be smaller. It will remain identical since keeping the image dimensions the same but reducing the resolution (pixels/in) requires the Image Size dialog to have the Resample Image option disabled (unchecked).

By the way, what the Image Size dialog calls resolution is typically used to size a document for printing. However, the fact you want to change the resolution from 300 to 72 suggests you want images sized for a monitor. If that is the case then only image dimensions should be your concern. The resolution for a monitor - whether it is 300, 500, or 72 - is entirely irrelevant. Only pixel dimensions matter.

Bicubic Sharper is the choice if reducing pixel dimensions.

< http://www.pixentral.com/show.php?picture=18pzmFKBscyPJ06qno gEysmKAiNd0>

i.e., from 300 dpi to 72 dpi. Nothing else needs to be changed. The image
dimensions will remain the same,

For the web? Not necessary.

http://www.leannehoad.com.au/temp/dpi_test.htm

--
Regards

John Waller

So you're recommending resizing in the browser, John? Or just saving images at roughly twice the file size needed for kicks? Or is it just the amazing typesetting that we're supposed to glean from your link.

Bicubic sharper WILL be better for sizing photos down.

In fact, the file size will not be smaller. It will remain identical since keeping the image dimensions the same but reducing the resolution (pixels/in) requires the Image Size dialog to have the Resample Image option disabled (unchecked).

As far as I'm concerned, this makes no sense twice.

Great job guys. I recommend admin do quick searches for the word "resolution", because there's some knee jerk shit going on when people write in about it.

what he's saying is that the ppi that is saved with the image is meaningless on the web (generally speaking). for web use, worry about the pixels x by y. it's generally best to save at the exact pixel size needed for the web page. scaling in the browser (i.e. style="width:30%; height:30%") will generally produce cruddy results.

per the original post:

I have about 200 hi-res photos that need to be changed to lo-res photos,
i.e., from 300 dpi to 72 dpi. Nothing else needs to be changed. The image
dimensions will remain the same, although the file size, of course, will be smaller.

nothing needs to be done, the file sizes will NOT be any smaller, that's what john's link shows.

As far as I'm concerned, this makes no sense twice.

maybe you should read it again, and get a cup of coffee. you seem a bit grumpy today. :)

here's another example from my site:
<http://aikodude.tripod.com/difResTest.html>

the top image is "72ppi" the bottom one is "300ppi". the file sizes are exactly the same. they display the same on the web. it's only when you go to print them (or if viewed in a browser that respects resolution, i can't think of one off the top of my head) that you see the ppi difference, which is defined only in meta-data.

J, when folks do that search for 'resolution' they will find threads that you have participated in.

<http://www.adobeforums.com/webx?128@@.59b5af3b>
<http://www.adobeforums.com/webx?128@@.3c0629a4>
<http://www.adobeforums.com/webx?128@@.59b502cd>

None of these threads seem to indicate that you have a solid grasp on the topic so your use of critical profanity seems very very odd.

John was only questioning if this was for the web as the mention of 72ppi always raises a red flag. There are very few uses for a 72ppi image. Since none of us know Homeboy's intentions, John's brief suggestion for web usage was all that was needed. You can wait to get your knickers in knots once we know what is really going on.

The original poster here.

The force of my question wasn't so much the efficacy of the re-sizing process, but more the process of automation. I know how to re-size a photo in PS (image, image size, click resample, change 300 to 72). The dmensions of the image remain the same, but the resolution is reduced and the file is smaller. I also know how to create an action to do this. And I understand how to run a batch process using this action.

But I wondered if there was a more efficient way of accomplishing this same thing, perhaps using Bridge or Lightroom, neither of which I am familiar with. Or maybe even there is a DIFFERENT way of doing it in within PS that is more efficient than what I outlined.

The lower resolution versions of these photos, by the way, will not be used for the web. I just need to get a series of smaller files to a customer so they can indetify the people in each photo. Previous I gave them a PDF contact sheet I made in PS (using the automated process), but for some reason they'd prefer to have individual files. I can send the the high res photos but that just takes up space unnecessarily. The photo dimensions are large enough so that at 72 dpi the content of the photos will be adequate. But in truth 72 dpi was an arbitrary choice.

but the resolution is reduced and the file is smaller.

if you UNcheck resample and change the resolution the pixel dimensions and the file size remain the same. if you CHECK resample and change the resolution, the pixel dimensions change and so does the file size.

Homeboy. So you are changing the resolution, but leaving the inch dimensions the same, which is what has confused some of the others, who think you meant that the pixel resolution will change. (Which of course it does not).

In effect, you are downsampling to give low resolution "proof" shots to the client to see, while holding back the larger resolution printable images. Sounds pretty normal photographic practice to me.

I suggest, if you haven't already, posting this in the Lightroom forum, where more Photoshop/Lightroom users hang out. There are a significant number of Bridge users here (although not me personally) but fewer Lightroom users, I think. I suspect most of the Lightroom users will know a bit about Photoshop.

My apologies.

Jim's right. No need to get my knickers in a twist. He (and HB) is also right that 72 ppi is pretty arbitrary.

J