Scanning Your Photos More Than 300 DPI Will Not Give You More Detail

Myth: Increasing Your Photo Resolution Higher Than 300 DPI Will Give You More Detail - Here Is Why This Is Wrong...

Once you understand a bit more about resolution, you can then control what you do with your photo scans.  For example, here is a story.

Gary, a client of mine, wanted to scan a few photos for his Father's 60th birthday.  He wanted to use the digital photo scans and create a slide show.  He told me that he was going to display them on a 52" HDTV.

I told him that 300 DPI scans will display at full HD quality.  So I scanned his Dad's photos at 300 DPI.  When Gary got the digital photos, he put together his slide show, and told me that the images looked great on HDTV. No problems with quality.

But the day before his Dad's birthday party he emailed in a panic.  He told me he went into a photo lab to print one of his digital photos as a poster.  But when he got his poster it looked horrible-- it was stretched, detail was missing, it just did not look right.  Naturally he thought that since the 300 DPI scans looked great on an HDTV, they would also come out looking great when printed at poster size.

Here is what can happen if you stretch a digital photo past its resolution:

This is where resolution gets confusing.  Come along and I will show you how you can use resolution and control what you do with your digital photo scans.

1) Your Physical Photos Have A Limit Of 300 DPI

If you look at a physical photo under a microscope you would see that it is made up of coloured dots.  This is how the photo lab developed your photos-- it printed minute, coloured dots to make up your images.  And the photo lab used 300 dots per inch to make the photo.  So, what you have there is a photo that is 300 DPI.

Now, if you take that 300 DPI physical photo and set up your scanner for 300 DPI as well, you will produce an exact copy.  What I mean is your digital photo will show the exact same details as your physical photo.

But what if you scanned your photo at 600 DPI.  It makes sense that if you double the DPI you would get twice the detail and resolution, right?  Not quite.  Remember you physical photo is only 300 DPI.  That is the limit.  So if you scan at a resolution more than 300 DPI you are NOT getting more detail.  You are not going in deeper and uncovering more detail.  Your photo's limit is 300 DPI... that is it!

2) You Pick Up Useless Detail Once You Go Higher Than 300 DPI

When you scan higher than 300 DPI you will start to notice other detail.  Not detail from the actual image itself.  But detail off the physical photo.  Your scanner will pick up the shiny gloss, minute dust and scratches, finger prints, oil off your finger prints.  You might not notice these thing with your naked eye.  But the higher the resolution, the more of this detail you will start to "enhance".

Anything under 900 DPI you will be safe.  After 900 DPI that is when you get into problems.  That is when you start enhancing all the artifacts like minute scratches.  So anywhere from 300 to 900 DPI you will be safe.

3) So Why Scan Higher Than 300 DPI

The one benefit of scanning higher than 300 DPI is that you get a larger image.  At 600 DPI, you get a digital photo that is twice the size of your physical photo.  Say you have a photo scan at 600 DPI.  If you walk into a photo lab and asked them to print that digital photo scan, you can print it at 8" x 12" without losing any quality.  Remember, you doubled the DPI from 300 DPI to 600 DPI.  Now the print shop has more dots to work with and are able to print an image that is twice the size.

But remember, it does NOT have more detail. All your scanner did was figured out mathematically how to convert a 4" x 6", 300 DPI physical photo into a 600 DPI digital photo-- WITHOUT losing quality.  It did not find any extra detail.  It just used the same detail and gave you an image that is twice as big.

And remember Gary's story?  His 300 DPI photo scans were perfect to watch on his HDTV.  But he was not able to print his digital photo at a larger size.  That is because his 300 DPI digital photos were exactly the same as his 300 DPI physical photos.  But if he told me he wanted to print out a few photos at poster size, I would have scanned them at 900 DPI. This would give him a photo that is 3x as big.  So he could have printed them at 16" x 24"

The More You Know About Resolution, The More Control You Have With Digital Photos

This is what I mean about having more control.  Say you never intend to re-print any photos at a larger size.  Then there is no point of wasting time scanning all your family photos at 900 DPI.  Scanning them at 300 DPI will be safe enough.  Plus, at 300 DPI you photos are HD quality.

But what if you want to "future-proof" your photos,  I suggest 900 DPI.  I scanned my family's photos at 900 DPI just because I never know if they will come out with a higher resolution HDTV.  Or maybe one day I will want larger re-prints.  I say it is always better to have too many pixels than too little.  But not too much-- going over 900 DPI you enhance what is on the surface of the photo.

If you like to go deeper into resolution, I get way more into resolution, here...

Understanding Photo Resolution: A Non-Technical Guide To See How Resolution Works

Good luck with your photo scans!
Konrad M.

HowToScan.ca