USMLE Study Guide

Cool The Sat Test images

A few nice the sat test images I found:

test of PNG version – blond-long-haired-woman-surfmorrobay.com_0279
the sat test
Image by mikebaird
testing the lossless .png version of a photo – I thought Flickr only took JPGs, but I see at flickr.com/help/photos/?search=tiff#18 that now lossless PNGs can be uploaded to Pro accounts. HOWEVER, note that all EXIF data is lost – so it is hardly worth the effort to save one’s images as PNGs – if the image is not to be further manipulated, it seems that a final save-as JPG in the highest quality level (12 in CS3 RAW converter) is the best compromise for saving images at Flickr. I wish I could save my .PSD file here.

Several formatted versions of this photo (.TIF .PNG .JPG) are in a test set www.flickr.com/photos/mikebaird/sets/72157602954969801/

This test PNG image is 6.81 MB vs 2.9MB for the highest-quality JPG version shown at www.flickr.com/photos/mikebaird/1849450523/ (for a factor of about 2X increased space).

PNG defined at en.wikipedia.org/wiki/Portable_Network_Graphics

Blond long-haired young lady woman watching the surfers at Morro Rock, Morro Bay, CA, Morro Strand State Beach taken from the parking lot, Sat. Nov. 03 2007 03nov2007 Photo by Mike Baird, Canon 1D Mark III w/ 600mm IS lens w/ 1.4X II tele-extender for 840mm, or tripod with gimbal head – bairdphotos.com flickr.bairdphotos.com photomorrobay.com surfmorrobay.com morro-bay.com

More info on using PNGs vs JPGs Vs TIFFs
en.wikipedia.org/wiki/Portable_Network_Graphics says in part (see link for full details):
JPEG can produce a smaller file than PNG for photographic (and photo-like) images since it uses a lossy encoding method specifically designed for photographic image data. Using PNG instead of a high-quality JPEG for such images would result in a large increase in filesize (often 5–10 times) with negligible gain in quality.

PNG is a better choice than JPEG for storing images that contain text, line art, or other images with sharp transitions. Where an image contains both sharp transitions and photographic parts a choice must be made between the large but sharp PNG and a small JPEG with artifacts around sharp transitions.

JPEG is a poor choice for storing images that require further editing as it suffers from generation loss, whereas lossless formats do not. This makes PNG useful for saving temporary photographs that require successive editing. When the photograph is ready to be distributed, it can then be saved as a JPEG, and this limits the information loss to just one generation. That said, PNG does not support Exif image data from sources such as digital cameras, which makes it problematic for use amongst amateur and especially professional photographers. TIFF does support it as a lossless format.

JPEG has historically been the format of choice for exporting images containing gradients, as it could handle the color depth much better than the GIF format. However, any compression by the JPEG would cause the gradient to become blurry, but a 24-bit PNG export of a gradient image often comes out identical to the source vector image, and at a small file size. As such, the PNG format is the optimal choice for exporting small, repeating gradients for web usage.

test TIF version -blond-long-haired-woman-surfmorrobay.com_0279_LZW-Compression
the sat test
Image by mikebaird
testing the lossless .TIF version of a photo – Note that while Flickr accepts TIF files, it converts them to JPGs – so there is no benefit of uploading TIF or TIFF files to try to preserve quality. I have a test version using PNG file format at www.flickr.com/photos/mikebaird/1884508548/ for comparison.
I thought Flickr only took JPGs, but I see at flickr.com/help/photos/?search=tiff#18 that now lossless PNGs can be uploaded to Pro accounts. HOWEVER, note that all EXIF data is lost – so it is hardly worth the effort to save one’s images as PNGs – if the image is not to be further manipulated, it seems that a final save-as JPG in the highest quality level (12 in CS3 RAW converter) is the best compromise for saving images at Flickr. I wish I could save my .PSD file here.

Several formatted versions of this photo (.TIF .PNG .JPG) are in a test set www.flickr.com/photos/mikebaird/sets/72157602954969801/

This test TIF image is 7.95 MB(using lossless LZW compression (see below); no compression was 19MB and too big for Flickr) vs 2.9MB for the highest-quality JPG version shown at www.flickr.com/photos/mikebaird/1849450523/ (for a factor of about 2X increased space).

PNG defined at en.wikipedia.org/wiki/Portable_Network_Graphics

Blond long-haired young lady woman watching the surfers at Morro Rock, Morro Bay, CA, Morro Strand State Beach taken from the parking lot, Sat. Nov. 03 2007 03nov2007 Photo by Mike Baird, Canon 1D Mark III w/ 600mm IS lens w/ 1.4X II tele-extender for 840mm, or tripod with gimbal head – bairdphotos.com flickr.bairdphotos.com photomorrobay.com surfmorrobay.com morro-bay.com

More info on using PNGs vs JPGs Vs TIFFs
en.wikipedia.org/wiki/Portable_Network_Graphics says in part (see link for full details):
Comparison with TIFF

TIFF is a complicated format that incorporates an extremely wide range of options. While this makes TIFF useful as a generic format for interchange between professional image editing applications, it makes adding support for it to applications a much bigger task and so it has little support in applications not concerned with image manipulation (such as web browsers). It also means that many applications can read only a subset of TIFF types, creating more potential user confusion.

The most common general-purpose, lossless compression algorithm used with TIFF is LZW, which is inferior to PNG and, until expiration in 2003, suffered from the same patent issues that GIF did. There is a TIFF variant that uses the same compression algorithm as PNG uses, but it is not supported by many proprietary programs. TIFF also offers special-purpose lossless compression algorithms like CCITT Group IV, which can compress bilevel images (e.g., faxes or black-and-white text) better than PNG’s compression algorithm.