How Can A 300 DPI Photo Scan Be The Same As A 1500 DPI Slide Scan

Learn More About Resolution And You Will Have More Control Over What You Do With Your Scans 

All you need to know are three numbers-- and the rest will be easy.  Lets begin.

1) The Physical Size Of Your Slide, Negative, And Photo

Take out a 35mm slide or negative.  Write this number down, it is important.  The actual size of your slide or negative is, 0.85” x 1.30”-- give or take a few points.

And the size of your physical photo is, well, 4” x 6”.

That is pretty easy.  But these numbers are important because what happens later.  But first, lets talk about DPI.

2) What Is DPI And How Many Do You Need To Scan Slides, Negatives And Photos

DPI or Dots Per Inch comes from back in the day when you had your photos printed at a photo lab.  The photo lab printed 300 colored dots on a 4” x 6” glossy sheet.  In other words, you got a 4” x 6” photo with 300 dots per inch.

Now move over to digital.  Instead of colored dots, we now use pixels.  Technically it should be PPI, but we still use DPI.  Anyway, you will see a setting when you load your scanner asking you what DPI, PPI, or resolution you want to scan your photo.

If you scan your photo at 300 DPI, you will produce the EXACT image as your physical photo.  That is because your physical photo is also 300 DPI.  If you double your DPI to 600, you will NOT double your detail or quality, you will just make your digital image twice as big.  Your digital image will be twice the size of your original, but maintain the SAME quality as your original.

3) How Do These Two Numbers Work Together And Give You A Digital Image

So far you know two numbers: the size of your original (slide, negative, photo) and DPI. What happens when you multiply these two numbers?  Here is what your scanner does with these two numbers.

Your photo is 4” x 6” and you scan it at 300 DPI.  Here is what you get...

4” x 300 DPI = 1200
6” x 300 DPI = 1800

Or 1200 x 1800.  This number is called your Pixel Dimension.  It is the most important number-- I will show you later why.

Now look at your 35mm slide-- it is about 0.85” x 1.30”, and say you scan it at 1500 DPI.  Here is what happens when you convert a 35mm slide to digital...

0.85” x 1500 DPI = 1275
1.30” x 1500 DPI = 1950

This number, 1275 x 1950, again is your Pixel Dimension.  

Can you see that your photo scan and slide scan have pretty much the same Pixel Dimension?  Have a look...

4” x 6” Photo scanned at 300 DP = 1200 x 1800 pixels
35mm Slide scanned at 1500 DPI = 1275 1950 pixels

Pixel Dimension is the most important number, and next I will show you why.

Conclusion: Forget About DPI / Resolution, Pixel Dimension Is The Most Important Number

Take a look at your computer monitor, HDTV, iPad, etc.  Every screen uses pixel dimension to display digital images.  For instance, my monitor is 1366 x 768.  My 52”, 1080p HDTV is 1080 x 1920.  An iPad is 1024 x 768.  Quick note: pixel dimension is also called screen resolution-- this is why resolution is so confusing, marketing uses the different names for the same thing.

So, what does this have to do with your scans?

Well, remember a 4”x6” photo scan at 300 DPI give you a 1200 x 1800 digital image.  That means even if you put it on your 1080p HDTV, it will display at HD.  That is because your HDTV is 1080 x 1920 and your digital photo is 1200 x 1800.

Digital Photo = 1200 x 1800
1080p HDTV = 1080 x 1920

This is why pixel dimension is the most important number.  Who cares about DPI-- that is not the true measure of resolution.  And you saw this where you have a photo scanned at 300 DPI and a slide scanned at 1500 DPI, and you get a pixel dimension that is pretty close to each other.

So, What Is The Best Resolution To Scan Slides, Negatives, And Photos?

That, my friend, is a different post.  Stay tuned and I will show you when you should use 300 DPI / 1500 DPI, and when you should go higher.

Thanks for reading, and good luck with your scanning project.

Konrad M.
Owner of ScanCanada.ca and HowToScan.ca

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

“Why You Should Never Use Digital Ice To Fix Your Slide, Negative, Photo Scans"

Here Is 3 Reasons Why You Are Not Getting Quality Scans Even When You Use Scan Enhancements Like Digital Ice -- And What To Do About It...
 
There is nothing more frustrating than learning all the features that came with your scanner, and you still get lousy scans.  No matter what you try, you cannot get consistent results.

If you are scanning your family's slides, negatives, and photos, and you are not getting quality scans like you expected, here is why.

When you rely on your scanner to edit your digital photos, then you will run into problems.  Scanners were made to scan pixels.  They are great at what they do.  But once you press that scan enhance button,  your scanner will do things to those pixels.

Here is 3 reasons why you should NOT rely on your scanner editing software.  And later I will show you how you can get quality scans.

1) You Have The Light Version Version Of Digital Ice / Scan Enhancement Features

Long ago Kodak designed the technology called Digital Ice. Basically Digital Ice looks for pixel consistency.  If it notices a cluster of white pixels that are surrounded by red pixels, it will fill it in.  Have a look...

Digital Ice will look for inconsistencies--  white pixels next to red.

Then it will fill in the white pixels.

Here is the thing.  Since Kodak owns this technology, it lincenses it out to scanner manufactures.

So if your scanner was inexpensive, you are most likely to have the "light" version of Digital Ice.  That means that not all those white pixels will be filled in correctly.  In fact, the wrong pixels might get filled in.  For example, sometimes I get scans with people missing eyes!  I guess my scanner thought that the whites of peoples eyes were dust.

I have a Nikon 9000, and it came with Digital Ice 4. At the time, this scanner cost me $6000. It does great a picking up pixels.  The pixels are sharp, clear, and full of digital data.  But once I press that Digital Ice button, all bets are off.  The scanner does a lot of wonky things to those pixels. I will show you below what I mean.

2) Colours End Up  Looking “Plastic”
   
No matter what I try, no matter how much I play around with the colour settings, some scans I still cannot get right.   Sometimes green grass comes out looking dark blue.  Or faded reds end up bright orange.  Have a look...

Sure, I have tried changing the colour saturation, colour levels-- but I still cannot get it.

And if I do get it, and think I have the colour settings just like I like it, I will have to change it for the next slide.  That is because not all photos taken are the same.  Some are taken in bright light or dark.  Some are taken indoors.  There is too many variables.


3) Digital Ice Removes Dust, Scratches AND Detail

But my biggest issue with Digital Ice and scan enhancement software, is that it takes away detail.  Here are two examples...

Digital Ice takes away detail.  In this photo it filled in the whites of eyes.

And, if you can see, the image on the right lost a lot of detail in the faces. 

Digital Ice does not know if a dust and scratch is important or not.  It will just fill it in.  And if you have an inexpensive version of Ditgital Ice, a "light" version, you will find more problems like this.  With my Nikon 9000 I see less of these problem.  But I still never use scan enhancement features.

So what can you do?  How can you get quality scans?

How To Get Quality Scans WITHOUT Digital Ice

Here is what I do.  I have been scanning since 2005 for a living, and I figured out how to get quality scans, even with a $200 scanner.

The first thing I do is I get a "natural" scan.  This means none of the scan enhancement features were used.  I only told my scanner to scan my slide, negative, or photo at a high resolution.

Next, I take the natural scan, and I edit by "hand" in Photoshop.  You can also use Gimp if you do not have Photoshop.

What if you have no idea how to use Photoshop or Gimp?  No worries.  As a side project I have a tutorial on how I scan my customer's slides, negative, and photos.  It is a free guide, and I try to make it as non-technical as I can.  Check it out here..

Free Guide: How To Scan Your Family Slides, Negatives, Photos Like A Pro

Editing your scans by "hand" is the only way I know how to get quality scans-- every time.  It is not hard too learn, and it does not take any longer than if you used Digital Ice.

Plus you get to learn a new skill you can show your friends and family how to do it.

Good luck with your scanning project!

Konrad M.
ScanCanada.ca

"3 Mistakes To Avoid When Scanning Slides, Negatives, Photos"

Here Are Three Quick Mistakes To Avoid When Scanning Your Slide, Negative & Photo -- And What To Do About Them

Maybe like me you went out and bought the most expensive scanner you could afford.  You learned all the instructions-- how to setup your scanner, what resolution to use, and how to use Digital Ice.

But no matter what you try, you still get lousy slide, negative, and photo scans.  Why is that?  I have been through it too.  But I managed to figure out how to get great looking scans.  

I have been scanning for a living for 6 years now.  Looking back now, here are 3 major things I have learned...

1) Do Not Think Resolution Is A Measure Of Quality 

Do not confuse a high resolution for quality.  All resolution is bits and bytes.  If your negative is really dusty, your 4000 DPI scan is going to show all that dust.  If your 60 year old slide has faded colors, setting up your scanner at 4000 DPI is NOT going to brighten those faded colors.

So what can you do?  Well, like me and most people you may have used your scanner's editing features.  But that is where another problem lies.

2) Your Scanner Was Not Built To Edit Your Scans

Do NOT rely on your scanner to fix your scans.  The minute you press that Digital Ice button, your scanner is going to do something wonky with all those pixels.

You will get faces with detail missing.  Your colors might be a bit off (grass comes out blue). Or your digital images are too dark or bright.

If you are frustrated with scanning your family's originals, this is why.

Here is the thing.  Today most scanners can do 4000 DPI.  It does not matter if you have a $200 scanner or a $6000 scanner-- they all pretty much do the same thing, which is scan at high resolutions.

The scanner manufactures know this.  So to compete they add as many features as they can.  More features, means a higher price.  Granted, my Nikon 9000 does a good at editing some scans.  But it is not consistent enough.  I still get about half the scans looking lousy.

What now? What can you do if you cannot rely on your scanner's editing features?

3) Not Getting Help -- FREE Help

Here is how I scan all my customer's slides, negatives, and photos.  First I produce a "natural" scan.  This means NO editing features were touched.  It is just a straight, 4000 DPI scan.

Next I open the digital image in a program designed for editing photos.  Digital Ice cannot come close to what Photoshop or GIMP can do.

You Do Not Need An Expensive Scanner To Get Quality Slide, Negative, Photo Scans

Or Be A Graphic Designer To Get Quality Scans...

If you want to get quality scans right now, with the scanner you already have, then here is what you can do, check out...

Free Scanning Tips: A Non-Technical Guide On How To Scan Your Family's Slides, Negatives, Photos

You do not need an expensive scanner, and you do not have to be a graphic designer.  I will show you, in a step-by-step process, how to properly scan your originals.

I will also be putting a lot more scanning tips, tricks and secrets... so stay tuned.

Good luck with your home scanning project!

This is Konrad,
HowToScan.ca