DPI and Why

The reason these thumb nails were so small was that it took so much time for the pictures to come
up on the page. When you clicked on an individual thumb nail; a larger version of the picture came
up (usually 4×6 or bigger), but it would take a long time to do so. I was just learning the web and I
did have access to Photoshop.

What I did was search through all the big shots; saved the ones I liked, and then brought them into Photoshop where I could compress them. I then made my own site with images that looked as sharp
or better than the original; but my pictures were 2 inch x 2 ½ inches, much better than all the really
small thumb nail shots I saw every where else. Through all my searching I found that over 90% of the images I was finding were saved at 72dpi; so that’s what I did. For several years, I saved all my
photos at 2 inch x 2 ½ inches and at 72dpi.

As my interest in photography continued to grow; I realized that a Sci-Fi web site might be cool but
it made me no money. I needed to put up a web site of my own photos. By now I was using a 56k
modem and decided my pictures needed to be bigger. When I scanned in my pictures I usually did
them at 100% at 72dpi; so that all my images on line where now 4×6 in size.

After a few years my lab started offering pictures on CD. They were also 72dpi so I didn’t have to
scan them in anymore. Life was good. They put images at these huge file sizes like 44 inches x 56
inches which I really couldn’t figure out. I didn’t know of anyone who would ever print something that
big; so again I took those images and compressed them down to 4×6 inch size.

Eventually, I started doing the same thing but saving them as 5×7 inch size. My new site (betterphototips.com) looked very impressive and actually loaded very quickly. Yes, I also eventually stepped up to real high speed (1.5mbs per sec.) Life was good; until I went back and started pursuing
one of my other great loves (writing). I figured rather than just using this site as a gigantic portfolio;
why didn’t I offer something for sale as well. You know the old adage “write about what you know
best”? To me it made perfect sense that I should write about photography. That’s when things started
to get complicated.

When I started looking around at self publishing and print on demand publishing, I found that they
all wanted the pictures to be 300dpi or greater. This was a total shock to me. I had thousands of
images that I was all ready to use, but they were all saved at 72dpi. I thought that Photoshop could
save me again, so I started converting them to 300dpi but something didn’t look right. It made no
sense to me at the time, but my 300dpi images looked worse than my 72dpi images. I was at a loss.
Then I went back and did my research.

The reason the images on the CD’s that come from the lab are so huge (in measurement) is so you
could use the images in either format. 72dpi is exactly 25% of 300dpi. If you want your 300dpi images
to look as razor sharp as your 72dpi images do on line, the print has to be 75% smaller. In other
words, an image that measures 44 inch x 56 inch at 72dpi would be the same quality as an image
that measures 11 inch x 14 inch at 300dpi.

If you take an image that was originally 5×7 inches at 72dpi and just try to convert it directly to 300dpi
at the same size, it will not turn out very well. Similar to the equivalent of the right f-stop and the right shutter speed, you have to take both factors into account! DPI and Size are forever tied together. You
can not change one without affecting the other. It is much easier to make something smaller that looks good, than to try to enlarge something after the fact and try to make it look even close to the original. The moral of the story is; ALWAYS save your images larger then you expect to use. Do not waste 15 years of your life and thousands upon thousands of images that can only be used in one way. Always save large!!