photography: 6 - megapixels and file formats

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