Get Quality Slide, Negative, Photo Scans By Understanding Resolution

The fact is that resolution is just bits and bytes. You may think that by adding more DPI (dots or pixels per inch) to a scan will give you more detail, you will go "deeper" in the scan and uncover something that you could not see. This is not true. And here is why...

1. Your Photos, Slides, and Negatives Have A Limit

Did you know your photos, negatives, and slides have a limit when it comes to resolution. Here is what I mean. Take a look at your photo. When you had that photo developed the print lab used a photo printer. And most photo printers printed 300 colored dots for every inch. In other words, your physical photos are 300 DPI (dots per inch).

So when you setup your scanner to scan your photo at 300 DPI, what you get will be an exact copy. But what if you went to say 600 DPI. Will you get more detail then?

Nope. Remember, your physical photo is only 300 DPI. And if produce a 600 DPI digital photo, it does not mean you have twice the resolution. You did not go "deeper" and uncover extra image detail. When you go higher than 300 DPI you will start scanning other detail you do not want. Detail like minute dust and scratches, hairs, oil from finger prints, the gloss off the photo, etc.

You will not uncover more detail when you scan your 4" x 6" photos more than 300 DPI. All you will do is make them bigger.

2. When You Increase The Resolution All You Are Doing Is Making Your Digital Image Bigger

When you scan more than 300 DPI, say to 600 DPI, what you are doing is making your digital photo 2x bigger. But you are not adding MORE details to your image. What the scanner is doing is producing the same quality image but twice as big. It is making sure it maintains the same quality of your 300 DPI photo but at 600 DPI.

But this is not a bad thing. Say you have an old picture of your Dad. It is his 60th birthday and you want to make a poster of his old photo for the party. So you scan the photo at 300 DPI and take the digital image to a photo lab. You ask them to make a 16" x 24" poster.

What will happen is, the photo lab is going to stretch a 4" x 6" photo into 16" x 24"-- and you will get a poster that looks horrible. But if you scanned your Dad's photo at say 900 DPI, and walked into the photo lab, now they have more pixels to work with. They will be able to print a 16" x 24" poster at the SAME quality of your 4" x 6" photo. That is all. Your poster will not look sharper, or have more detail. It will be the same quality as your 4" x 6" photo, but at 16" x 24".

3. How To Get Real Quality

Now you know that resolution is just bits and bytes. And by upping your resolution (DPI) to something huge does not mean you will get more detail. You are just making the digital image bigger.

So how do you get real quality?

First, make sure your scanner can pickup sharp, clear, pixels. How can you tell you have a quality scanner? Well, I have been scanning for 6 years for a living. I have used many types of scanners-- high end scanner to affordable home scanners. And to be honest, a simple home scanner, one for around $300 is good enough. Of course my high-end scanners use more sensitive technology to pickup pixels.

But honestly, most scanners are built the same. When you buy anexpensive scanner, all you are paying for is all the features. The scanner manufacturer's know scanners can do the same thing-- scan at high resolutions. But to get you to buy their scanner, they add bells and whistles like Digital Ice or other scan enhancement features that promise quality scans.

Second, do not rely on your scanner to edit your slide, negative, and photo scans. Your scanner is meant to scan-- it is amazing at picking up a lot pixels. But once you press any of those fancy-sounding features (Digtital Ice, ROC, Colour Fix, etc), your scanner is going to do something wonky with those pixels. I never get consistent results when I use my scanner's image enhancement features.

What I do instead is edit my scans by hand.

You might say, "thanks for the help, but it is just easier to press a few buttons and let the scanner do all the work". True. But here is the thing. These are your only copy of your family's originals. And digitally archiving them is a big job. So if you are going to take all that time scanning them anyway, you might as well go all the way and make sure you scan them right the first time.

It is always tempting to take the short-cut, but after you learn some editing techniques and scanned a few, you will get more efficient. Plus you can teach your family and friends on how to edit digital photos once you are done.

If you like to learn how to edit your scans, I have a step-by-step guide here...

HowToScan.ca

Even if you have never used photo editing software, I will show you how to do edit your scans, in a non-technical way, step-by-step.

Good luck with your home scanning project!
Konrad M.

When your scanner converts analog into digital, this is what it does: the scanner takes the physical size of your original (photo, slide, or negative), and "squeezes" as many pixels you tell it to for every inch of that original.

In other words, here is what I mean. Take a look at your 35mm slide-- the physical dimensions are around 0.85" x 1.30". When your scanner is setup for, say, 1500 DPI, this is what happens when I mean "squeeze"...

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

Or you can say your 35mm slide scan was converted into a 1275 x 1950 digital image. This number, 1275 x 1950 is called the "Pixel Dimension". Write this down, and remember it. Why? Because this number is the only number computers understand. Your HDTV, computer monitor, iPad, etc. will look at the Pixel Dimension. They do not care about DPI, resolution, mega pixels-- they only look at the pixel dimension to display your digital image properly.

To put this into perspective, lets see what happens when you scan your 4" x 6" at 300 DPI...

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

So your digital image has a pixel dimension of 1200 x 1800. But wait... you scanned your slide at 1500 DPI and your photo at 300 DPI, and still got pretty much the same Pixel Dimension?!

35mm slide scanned at 1500 DPI = 1275 x 1950
4" x 6" photo scanned at 300 DPI = 1200 x 1800

You see, this is why DPI is not important. What is important is the end product-- the Pixel Dimension. Even though you used different DPIs, you still got the same digital image.

Oh, and how do you get mega pixels? You multiply the pixel dimension...

1200 x 1800 = 2.1 million. Or in marketing language, 2 mega pixels sounds sexier.

But is a 1200 x 1800 digital image good enough? 2 mega pixels seems pretty small. Is that good enough quality?

Once you read the rest, all of this will come together, you will start to see how all these numbers mean the same thing and all work together.

Want to discover more about resolution? Click on the link below...

http://howtoscan.ca/resolution/what-is-resolution.html

Good ol' marketing. 1080p sounds way better than 2 mega pixels. And I know I would not buy my HDTV if they said it is only 2 mega pixels.

But the fact is 2 mega pixels is enough for true HD quality. And remember when I told you that scanning your photos at 300 DPI and slide/negatives at 1500 DPI will give you 2 a mega pixel digital image? Well, if you put those digital images on your HDTV, they will be displayed at true HD quality.

But what if you scanned your photo at 600 DPI-- would your HDTV show more detail?

No.

Just like your physical photo has a limit of 300 DPI, your HDTV has a limit too-- at 1080 x 1920.

So if you scan your photo at 600 DPI, you would get a 2400 x 3600 digital image. And if you displayed that image on your HDTV, your TV will reduce the pixel dimension back to 1080 x 1920.

But no worries. You will NOT lose quality. Back in my first article I said that when you scan at a resolution higher than 300 DPI, all you get is a bigger digital image. You do not get extra detail or quality. Well the same thing happens but in reverse when your HDTV reduces the size-- it mathematically reduces the size AND at the same time maintains the detail and quality.

To put it perspective-- did you ever have a 32", 1080p HDTV? Then when you upgraded to 52", could you see more detail? No, your TV just got bigger. It maintained the same detail, and just displayed it at a larger size.

Learn more about how your scans and HDTV work together here...

http://howtoscan.ca/resolution/hdtv-resolution.html

The first step when you start up your scanner is to know what DPI you are going to scan your slides, negatives or photos. If you are unsure what the best DPI you should use, here is a quick answer...

For photos, if you want to maintain the SAME quality as the original, scan them at 300 DPI. If you want to make, say a 4" x 6" photo twice as big, scan it at 600 DPI. But remember, you are NOT adding detail, you are just making the digital image bigger. I scan all my photos at 900 DPI, which gives me an 19 mega pixel digital image. Here is how that works again...

4" x 900 DPI = 3600
6" x 900 DPI = 5400

I end up with a 3600 x 5400 digital image. And 3600 x 5400 = 19.4 million, or 19 mega pixels.

For slides and negatives, if you want to maintain the same quality do not go under 1500 DPI. I scan my slides and negatives at 4000 DPI. Here is how that works...

0.85" x 4000 DPI = 3400
1.35" x 4000 DPI = 5400

The actual dimensions change from slide to slide, but on average my slides and negatives are about 0.85" x 1.35". Anyway, the pixel dimension is 3400 x 5400, or 18 mega pixels.

If you have different size slides or negatives, here is what I scan them at...

http://howtoscan.ca/scanning-basics/film-format-types.html