steve wrote:
Hi all
I have always have a problem understanding that, can someone please explain it to me.
I need to make image size (similar too A4 format) 215mm x 260mm and 300dpi
but if I change the Resolution for example to 50dpi that changes the image size to
and if I go with 300dpi it look like it is too big for A4 size Can some one please give me a quick lesson
Thanks
Perhaps it will help if I take a shot at explaining what is going on here.
Your original image contains a certain number of pixels across and a certain number down. That's all that you image has. It knows nothing about size.
For the sake of argument let us assume that you have an image that is 1024 pixels across and 768 down.
If you tell Photoshop that you want this image to be at 256 dpi *AND* if you have the "resample image" box unchecked, it will tell you that the image is 4.00 inches across and 3.00 inches down.
If you tell Photoshop that you want this image to be at 128 dpi *AND* if you have the "resample image" box unchecked, it will tell you that your image is 8.00 inches across and 6.00 inches down.
In neither case has the number of pixels changed.
Alternatively you could set the dimensions and see what dpi you would get.
On the other hand, if you check the "resample image" box, Photoshop will attempt to add or subtract pixels as needed in order to meet your specifications.
With the "resample image" box checked and a size of 8x6 chosen and 128 dpi used, no resampling will be done as the original image will meet those specs. But if you now pick 16x12 as your desired image size at 128 dpi, there are not enough pixels to meet that goal.
So Photoshop will generate new pixels using the method chosen in the little choice box next to the "resample image" box. In this case your new image will have 2048 pixels across and 1536 pixels across (and your image will be four times its original size) but at most 25% of the pixels will be your original ones.
The resulting image may well be fine for your purposes.
If you downsize the image by specifying a dpi and a size, Photoshop will comply by generating an image from yours
with the needed pixels. It is likely that all the pixels in the new image will have been calculated by Photoshop.
So the idea is simple. It is the "resample image" box that controls how the image is resized. With it unchecked the image is UNCHANGED and Photoshop just shows you how
many dpi you'd get at the requested size or what the size would be at the requested dpi.
With it checked Photoshop will honor your requested dpi and dimensions and adjust the number of pixels to meet that.
Does that help?
---- Paul J. Gans