Picture size

Hi, was wondering if anyone could tell me what the resample box does for you when you are sizing your pictures?

Thanks,
Teeny

Hi Teeny, it's a very good question, and an extremely important concept to understand.

Basically, it's the difference between changing your image's pixels, and not.

Watch what happens if you change your image size without resampling. As the physical dimensions of you image get larger, the resolution gets lower, and vice versa. Importantly, the pixel dimensions and file size don't change at all - eg a 6 megapixel image remains a 6 megapixel image. If you do this, you won't see your image change size on screen at all.

Now watch what happens if you turn resample on. As you change the physical dimensions of your image, the resolution remains the same, so the pixel dimensions and file size change instead. Your image will change size on screen.

Some people are strangely anal about this, and wouldn't resample their image even if you held a gun to their head. While I don't feel so strongly about it, I would certainly say that it's not necessary to resample your master image. Perform all your editing on the exact pixels that came out of your camera.

Only when you're making a copy of your image for output would you resize it. In my workflow, I nearly always use the Crop tool for this. If you enter dimensions* but no resolution in the Options bar for your Crop tool, your crop won't resample your image. But if you enter a value in the Resolution field as well, then your crop will resample your image, which is why you'll see it change size on screen.

I hope I've explained this clearly. I'm sure other people will be along to clarify.

*Refers to physical dimensions. Pixel dimensions behave differently.

teeny wrote in post #6978051
Hi, was wondering if anyone could tell me what the resample box does for you when you are sizing your pictures?

Thanks,
Teeny

Uhm, in what program? I can't tell you what it does if I don't know which program you use to edit with.

Resampling interpolates the existing pixels to either increase the number of pixels or decrease them.

The most often uses would be 1) if you are printing at a very large size, and you want total control over the final appearance/sharpness of the file you would resize with resampling turned on to the desired size then apply final sharpness and other adjustments, 2) if you work with a printing lab that requires a particular resolution for any given size (such as 300 ppi) and 3) if you need to reduce an image display size for something like the Web and want to fine-tune something like sharpening tailored for the smaller size.

In practice, I personally don't print at a size that requires explicit resampling, but I do my own printing on 13"x19" paper, which handles the "smaller" resolutions of all my cameras. If, though, I needed a truly large print (or wanted, say, a 12" print of a crop) I'd consider doing some resampling. For my Web output I've never seen much advantage to resampling, but I'm not putting out a professional Web gallery.

tonylong wrote in post #6978977
For my Web output I've never seen much advantage to resampling, but I'm not putting out a professional Web gallery.

Huh??? LOL, your website must be very very slow to view, with all those 10MP images!

Thanks everyone. Dano , that was a good explanation. I appreciate it.

Teeny

Damo77 wrote in post #6978993
Huh??? LOL, your website must be very very slow to view, with all those 10MP images!

Heh! I meant "explicit" resizing, but I guess I coulda shoulda mentioned that my Lightroom Export function automatically resamples to Web size. D'Uh for me to neglect that!