Can I change the size of my digital photographs all at once?

I have hundreds of digital photos from a recent trip that are, alas, in “Freakin’ Huge!” format (about 2500+ pixels). Is there any way (or any software) that will allow me to change them all to a more manageable size (about 4" x 6" printed) all at once rather than individually?

Yes. Photo Shop Elements File/batch processing, and you can send them to a different directory, or sub directory. It will change every one of the specified files to the new size.


Nitpick: Resolution (total number of pixels) and size are actually independent; it depends on the dots per inch of your output device, and generally you can print an image with any number of pixels at 4x6, with varying quality levels. “4x6 print” doesn’t imply any particular number of pixels, I’ve printed images from both my 1 MP and 6MP cameras at 4x6 (they’re not indistingushable, but pretty close).

To answer the question, though, yes. Photoshop can make a “droplet” that you can just drop all your images on to reduce resolution. I don’t know if Photoshop elements has the same capability or not.

GraphicConverter, which is much cheaper, also has the ability to make batch-processing “droplets” – I’d be surprised if it couldn’t downsample (one of many techical terms for what you want to do).

There is also a shareware program (free to try) called Irfanview that will allow various batch processes, including renaming, resizing and file type conversion. A quick Google should provide a download site.

irfanview, iirc, can do batch resizing and is free.

I use Mihov Image Resizer, a free utility that can batch process images to resize them, or convert them between BMP, GIF & JPG formats, or rotate them.

I’ve tried Irfanview and was disappointed at the results of its resizing. It looked as if it simply removed pixels as neccessary without attempting to smooth out the result, so a lot of the images came out with “jaggies”. I wound up creating a macro for Paint Shop Pro that does resizing and am much happier with the results.

Nitpicking your nitpick: Resolution and size aren’t “independent”, they’re fictional. For any given image, you have a two-dimensional array of pixels that are n pixels wide, and n pixels high. Each of those pixels is described as being a particular color, expressed as a numeric value. That mosaic of pixels makes up the image. How those pictures are spread across physical space determines the “size” of the image; assuming a specified size for the image, the resolution is a simple matter of dividing the number of pixels in each dimensions by the size in that dimension.

All of these are technically independent of any output device you may use to print the image. As the nominal resolution of the image decreases (i.e., as you spread the fixed number of pixels you have across a larger physical space) the visual quality of the image decreases. At resolutions above about 100 pixels per inch, most commonly used ink jet printers will produce acceptable, though not outstanding, results. For the highest quality prints, you’ll typically want a somewhat higher resolution – up to about 300 dpi. In other words, for a 4 inch by 6 inch image, you’ll want to have about 1200 x 1800 pixels.

All of the preceding paragraph assumes an ink jet printer producing composite full color images. If you’re preparing materials to be printed by offset lithography, different rules apply.

nitpicking your nitpick of a nitpick, resolution refers to the raw number of pixels in an image. The dpi refers to how closely packed they are ie: pixels per inch.

It’s possible that in some contexts at least you’re right, but none that I know of, either theoretically or practically. As an exercise, pick any image editing program you choose and view or change the value designated as “resolution”. In every case I’m aware of, that value will be the number of pixels per unit of measure, typically either inches or centimeters. It’s true that for digital cameras, the number of pixels captured (horiz. pixels X vertical pixels) by the CCD array is used as a measure of quality, and I suppose there may be instances where that’s referred to as “resolution”; for instance, the spec sheet for the new Nikon D50 refers to its “high resolution” in the context of its discussion of the camera’s capabilities:

But on the back, in the technical specifications, the word “resolution” does not occur. There’s “effective pixels” (6.1 megapixels) and “image size” (3008 x 2000 pixels), but no “resolution”.

I 3rd using Irfanview for batch image resizing and resampling. For the money, you get a lot of other great features as well.

If you’re using Win XP, you can use the Image Resizer, downloadable from the sidebar of this page. It’s quite good, easy-to-use, and fast!

Why do you say 2500+ pixel images are difficult to manage? I wouldn’t recommend throwing out the original 2500+ pixel image files. You lose image quality by resizing. 2500 pixels isn’t overkill for printing to 4x6".

The only time you’d want to resize images is if you’re sending them by e-mail or uploading them to a web page. If that’s the case, Picasa from Google is a pretty good program. Just select the ones you want to resize and select “Export pictures to folder”. It will not touch the original files, but save resized copies in the specified folder. You can also use Picasa for managing the original full-size image files.

I think most people use ‘resolution’ to mean the no. of pixels, basically as an extension of how ‘resolution’ is used wrt displays, i.e., ‘screen resolution’. For a given screen, the no. of pixels is indeed directly related to resolution, however for different screens with the same ‘screen resolution’, the resolution will in fact often be different (if the screen size, etc. is different). IYSWIM.