Nikon D200 File Formats

Nikon D200 File Format Comparison
© 2006 KenRockwell.com

I bought my D200 and 18-200VR from Adorama here. I also bought another from Ritz here. Also try Amazon here for the camera and here for the lens. Adorama usually has D200/18-70 kits in stock here.

INTRODUCTION

Raw or JPG?

If Raw, should you use compressed or uncompressed?

If JPG, should you use FINE, NORMAL or BASIC? Should you use Size Priority or Optimal Quality JPG Compression? How about Large, Medum or Small image dimensions?

Let's make some tests and compare resolution, artifacts and sharpness.

The good news is that these images are all sent with extremely high quality so nothing, not even the artifacts, are altered. The bad news is it will take forever to load over a dial-up Internet connection.

I used the Raw + JPG mode to make pairs of identical images for comparison.

Feel free to skip to the examples if you're fluent in the terminology.

TERMINOLOGY

Image Size

Image size is measured in pixels. In the D200 they are called Large (3,872 x 2,592 pixels), Medium (2,896 x 1,944) and Small (1,936 x 1,296).

Raw data can't have it's image size changed in-camera. JPGs can be saved in these different sizes.

Raw

All cameras create an image from raw data sucked off the sensor. Most cameras create JPGs with it and then throw the raw data away.

Fancy cameras allow you to save this data so you can screw with it later in software on your computer. Software does the same thing to create images from the raw data that the camera's hardware does. Software is much slower than the hardware that does the same thing in the camera. That's why cameras can spit out JPGs at 5 per second, but your computer probably takes 10 seconds to open just one raw file. Each is doing exactly the same thing to the same data.

If you want to save the raw data you can save it as the random data from the sensor. This is called uncompressed raw. Nikon's version is called NEF.

Compressed Raw

Since this data is mostly random, it can be compressed losslessly to save a lot of space. It later can be reconstiuted (decompressed or expanded) exactly and used the same as raw data. it saves half the space! Nikon uses lossless compression of the data, but is clever enough to map 12-bit data to 10 bits to save more room.

JPGs

The camera creates images from the raw data.

The camera then uses a very clever trick called JPG compression to make a much smaller file from this image while keeping the same image size and resolution.

Just as slugs can't comprehend the cosmos, laypeople without PhDs in mathematics can't comprehend how JPGs retain image quality. One day I'll explain how JPGs use gamma conversions, discrete cosine transforms, quantization matrices and Huffman coding to pack 14 bit linear raw data into 8 bit jpgs. Don't worry, JPGs work great as I'll show.

File Size

File size is measured in MegaBytes, MB. There is no direct way to set this on the D200.

File size depends on the image size in pixels, the amount of detal im the image, the level of JPG qualty desired, and the

JPGs can compress more if there is less detail in an image. A flat image of a blank sky requires very few bits.

GUIDE IMAGE

Here's the overall image from which the 100% crops below are taken. I made these with my 55mm Micro lens at f/5.6, the sharpest thing I've got.

guide image

Guide image, full frame. Each image below is a 100% crop taken from the red area.

Uncompressed NEF vs. JPG BASIC, Size Priority

This compares a 16 MB uncompressed NEF with the crummiest 1.2 MB Large (3,872 x 2,592 pixel) JPG you can get.

There is an obscure JPG compression menu option in the D200 and D2X: Size Priority and Optimum Quality. Size Priority, shown here, is the default and the only option in cameras like the D1X and D70 which don't offer this.

Roll your mouse over the image to see the NEF. Move the mouse away to see the JPG.

They look pretty much identical, with the JPG having the same resolution, just with less sharpening than was used by the NEF.

Add USM to Make Them Match:

Let's add some sharpening to the JPG and see if we can make them match.

I added some delicate sharpening at 0.3 pixel radius, 100% to the JPG. See how they compare now:

Now they look identical, except for some minor contrast variation and some barely visible JPG artifacts. Unless you know how to look the artifiacts are invisible and certainly don't affect the picture.

Not bad for the crummiest JPG setting!

If you do know how to see the artifacts, let's crank up the quality and see what happens.

Uncompressed NEF vs. JPG BASIC, Optimal Quality

On older Nikon DSLRs you can get this same improivement by going to NORMAL JPG.

I like to keep my files sizes small, so I use the obscure Optimize Quality JPG option buried in the D200 at MENU > SHOOTING (green camera icon) > JPEG Compression > Optimal Quality. Once set it stays this way even when the camera is green-dot reset. This mode gives smaller files than NORMAL and better quality than BASIC, or in other words, the quality of NORMAL with the file size of BASIC.

This Optimal Quality JPG compression option lets the file size grow to the same size as NORMAL if the subject needs it, and lets the file size shrink back to BASIC if it's not needed. The default Size Priority option keeps the files sizes the same, regardless if thhe subject demands it. Busy, detailed subjects need more JPG bits to get the same image quality than do flat images. The Optimal Quality option lets the camera allot bits intelligently based on the subject, instead of making big files when they aren't needed for flat subjects like blank skies.

Here's the same thing at JPG BASIC, Optimize Quality. Roll your mouse over the image to see the uncompressed NEF for comparison.

Now they look the same. The minor artifacts from the BASIC Size Priority JPG are mostly gone. This is why I shoot at this setting:

Medium, resized, USM 200% @ 0.3 pixels

Small size, resided to match, 250% USM at 0.3 pixels

Details:

Nikon makes this easy with the Raw + JPG mode. I get two files of the same image, differeing only in format! it makes these delicate comparsons possible.

I opened each file in Photoshop and cropped them. They were saved at 80% in Save to Web, which shows you exactly what I was seeing on my screen.

To open the NEFs I used Nikon's free NEF opener that comes with the camera. Any other NEF opener, like Photoshop's Camera RAW or other third party openers, don't have acess to Nikon's secret sauce curves and will have different colors. Then the NEF colors won't match the JPG. Since the free opener opens in Nikon sRGB instead of IEC 61966-2.1 sRGB I converted the NEF to the same colorspace. Note that the NEFs still don't match color and contrast exactly, but close enough for the purposes of seeing how if you can see any loss of image quality in the various formats.

The smaller JPGs were resized in Photoshop using bicubic Sharper, and to match the size of the NEF. The mediom resized to 3865 wide. The small JPG was resixed to 3871 pixels horizontallty to match the NEF

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