Hi, I am Herman, I am new to this site, hello to all.
my question is , how can I enlarge a photo in photoshop, for example if the photo is 11x5
how can I make it 100x50 and what should be the resolution.
thank you.

Hi Herman, You've probably figured this out by now (it's an old post), but just in case...

The minimum resolution that you will want for printing is typically 300dpi. You then multiply this by the image size you want. So, for example, if I wanted to make a 4x6 print, I would want the image resolution to be 1200x1800 (4x300... 6x300). You'd then want to go into the Image Size dialog box in Photoshop (go to the Image drop-down menu and then select Image Size). Make sure the "Constrain Proportions" box is checked and then enter your numbers (1200, 1800, or whatever your size calculation worked out to be) in the Pixel Dimensions section (make sure the drop-downs here are for pixels, not percentages). At the bottom of the box, it has a drop-down for Resample Image. Make sure this box is checked and then select Bicubic Smoother if you are making the photo bigger than it is now, and Bicubic Sharpener if you are making it smaller than it is now. Click OK and your image is resized! It's important to then zoom in to the image to view it at 100%. There's a limit to how much you can enlarge an image, so here you are looking to see that the image is still sharp and of good quality.