• DNG = 1,922 KB
• BMP = 3843 KB
• TIF = 3822 KB
• JPG = see graph
• Vault = varaible

Images downloaded from EFS-1 are raw, unprocessed images in a format called a Digital Negative. Upon download to your computer we assign an extension "DNG" to each image file. Digital negatives are image files stored in a format which is unique, or proprietary to EFS-1. A digital negative is what we call a "raw" image. It is technically defined as a "Bayer" pattern.

As Digital Negatives are opened, the EFS-1 User Interface applies color science algorithms to the Bayer (DNG) image and converts the digital negative into a viewable thumbnails and subsequently to a viewable image with a spatial resolution of 1280 x 1024 pixels.

Please note that the spatial resolution of every EFS-1 image is 1280 x 1024 pixels, for a total of 1,310,720 pixels. We refer to this as 1.3 MegaPixels. This never changes. Every image has the same resolution. (The only way that you can change the resolution of an image is if you make a deliberate change to an image after downloading, using an image editing program such as Photoshop.)

After digital negatives have been displayed in the EFS-1 User Interface window you have four choices:

1) Save As JPG

2) Save As BMP

3) Save as TIF

4) Transfer the image to an imaging application (such as Adobe Photoshop).

Each of these transactions will result in a different file size.

1) If you elect to Save As JPG you may select the compression level. You are presented with a sliding scale of compression from level 50 to level 100, inclusive. This offers you 51 possible choices of JPG compression. The resulting JPG image file can range from 1.5 MB to 100 KB in file size. Regardless of compression, the resulting file will retain the spatial resolution of 1280 x 1024.

2) If you elect to Save As BMP you will get a BMP file of size 3.750 MB (3,840 KB, or 3,932,214 Bytes). The resulting file will retain the spatial resolution of 1280 x 1024.

3) If you elect to Save As TIF you will get a TIF file of size (similar to a BMP) 3.751 MB (3,841 KB, or 3,933,402 Bytes). Note that the EFS-1 UI/Data Source offers TIF with no compression. The resulting file will retain the spatial resolution of 1280 x 1024.

4) If you Transfer the image to a Twain-aware imaging application you have even more choices. Let's take Photoshop as an example. From Photoshop you may save as JPG or BMP with virtually identical results as described above. However, if you Save As TIF, Photoshop will offer two additional choices: no LZW, or LZW (lossless compression).

Selecting TIF without LZW results in a TIF file of 3.755 MB (3,845 KB, or 3,937,356 Bytes), which is similar to choice 3, above.

Selecting TIF with LZW results in a TIF file of 2.617 MB (2,680 KB, or 2,744,054 Bytes).

Note: Keep in mind that the final image is 3.9Mb in 8bits and 7.8Mb in 16bit mode.

To make things more complicated, Photoshop allows you to embed a color profile in an image. This will add slightly to the file size.

The DIMA image on our website was shot with an EFS-1, using a Nikon N90 camera at the DIMA/PMA conference & tradeshow held in Orlando in February 2001. The image was downloaded as a DNG and then transferred to Photoshop. From Photoshop the image was cropped slightly to 1276 x 1024. Then it was saved as a TIF using LZW compression with an embedded ICC color profile for a final file size of 2,706 KB. This is very close to my observation of 2,608 KB. (Reduce the file by four columns and then add the profile.)

When an image is viewed in Photoshop (any image - compressed or not), there is a number in the lower left hand corner. The formula for this is: (X pixels) * (Y pixels) * ( 8 bits per color channel * 3 color channels) / (8 bits per byte) /1024/1024 M.