Upload
mike-cummins
View
707
Download
0
Tags:
Embed Size (px)
DESCRIPTION
All you need to know about megapixels and digital file formats
Citation preview
Film and CMOS sensors capture images in completely different ways:
8 hour exposure
Joseph Nicéphore
Niépce
10 minutes exposure
<<
< 1
76 P
ixels >
>>
By Kodak
Film is roughly the equivalent of 25 megapixels
Video on next slide…
http://www.youtube.com/watch?v=lGeAu2RQcmw
aka Dots per Inch / DPI
This has nothing to do with taking a photo!
PPI is about the quality you print your photo at…
PPI is how you use all those megapixels…
Do you cram 300 into an inch and print a high quality picture at 6” x 4”…
…or do you print a 8” x 12” photo at a lower quality picture of 150 ppi?
Aim to print at 300 ppi
Incidentially, if you’re sending a photo over the web you want to use 72 ppi and low megapixels (less than 1 maybe?)
PPI is also important when scanning photos
Find out the highest optical setting for your scanner and use that (usually 600+ ppi)
MoreMegapixels =Good
…except if you’re emailing your photo!
Shoot at thehighestmegapixels yourcamera has
1 - Proprietary
Files types used by specific software, such as:
These tend to be copyrighted
1 - Proprietary
Photoshop= PSD GIMP = XCF PhotoFiltre = PFI Pixlr = PXD
…some programs can open and/or save in another’s propriety format – but usually at a cost
2 - Lossy
Most digital photos are compressed in some way
Lossy compression throws away information within a photo…
2 - Lossy
The best known lossy format is:
Most cameras take their photos as
JPEGs
Because how much information it throws away can be adjusted…
2 - Lossy
Lossy compression throws away information in an image to make smaller file sizes…
2 - Lossy
Lossy compression throws away information in an image to make smaller file sizes…
2 - Lossy
Lossy compression throws away information in an image to make smaller file sizes…
2 - Lossy
Lossy compression throws away information in an image to make smaller file sizes…Quality:
100%
60%
30%
An uncompressed file can be very large
Quality: 100%
Quality: 30%
So an uncompressed image would take longer to write to your camera’s memory card…
…and who wants to wait 20 seconds between taking photos?
It’s a great format for the Internet where file size is the determining factor
3 - Lossless
Lossless compression rewrites the information in an image in ‘shorthand’…
3 - Lossless
Lossless compression rewrites the information in an image in ‘shorthand’…
3 - Lossless
Lossless compression rewrites the information in an image in ‘shorthand’…
3 - Lossless
Lossless compression rewrites the information in an image in ‘shorthand’…
3 - Lossless
Lossless compression rewrites the information in an image in ‘shorthand’…
R3B2R2GR
41 characters
28 characters
15 characters
8 characters
3 - Lossless
And the beauty is, that when the image is reopened all the original data is restored…
R3B2R2GR
3 - Lossless
The drawback of lossless compression is that while it produces better quality than JPEG the files are still pretty big
Formats include: TIFF, PNG and BMP
Raw is a format used on (mainly) digital SLR cameras
Raw is a lossless format that gets around the problem of a slow write speed to the camera’s memory card
How…?
http://www.youtube.com/watch?v=Qsi71MEFPB8
Raw does not create the actual photo image in the camera, it simply stores the raw data to be converted to another format at a later date
So the quality of the photo you take on your camera is always better in Raw
Great, but…
There’s no standardised format! Every manufacturer uses their own Raw format!
So not all editing software will open a Raw file – you may need to convert them using the software that came with your camera
File sizes are still 6x the size of a JPEG
If you can, shoot in Raw
Always shoot with the lowest amount of image compression
Save Photoshop (or similar) work files in propriety formats, then convert your finished work in more widely used format