Kodak Z612 JPEG File Compression

[ac.smith]

A poster in another forum asked why the files sizes on his Z712 varied so much compared to another camera. He based this comment on the observed range and while it is a measure of variance it leave something to be desired. So I have just ran some statistics on file sizes from my Z612 with both standard and fine compression set at 2382x2128 resolution (6MP with a generous round up.) I used as samples all the photos I took at the 2007 QC Auto Show (standard compression) and the 2008 QC Auto Show (fine compression). One sample size was 100 and the other was 101.

Fine Standard
Mean 2.28MB 1.90MB
Std Dev .24 .22
Min 1.69 1.08
Max 2.92 2.56
StdD% 10.44% 11.84%

On the average a fine file is 47.3% the size of the image and standard file is 39.3% of the image. The actual variation of file sizes is slightly greater for standard compression compared to fine compression.

Since it was questions of image quality that raised the topic to begin with I decided to do a quick set of tests to see haow much of a effect the compression ratios had on IQ. I'll let you draw your own conclusions.

First is the full photo resized to 640x480.

[ac.smith]

100% crop of fine compression.

[ac.smith]

100% crop of standard compression.

[ac.smith]

100% crop basic compression. By the way the original EXIF data is attached to all images. The white dot that barely shows on the full frame shot and is quite obvious on the 100% crops is not a "hot" pixel. I examined the subject again closely and found a tiny!! piece of metalic glitter which created the hot spot.

[mtclimber]

AC-

That is an interesting comparison. Fine seems to be the way to go, or at least it has worked quite well for me..

Sarah Joyce

[ac.smith]

I use fine as a matter of routine now but I would be very hard put to sort which was which with these samples without the labels.

A. C.

[Alan T]

mtclimber wrote:

...Fine seems to be the way to go, or at least it has worked quite well for me...

It will certainly work well for everybody, so far as image quality is concerned.

However, I did test exposures immediately I bought my Z712 (as with all its predecessor digicams, starting with 3Mp Olympus C3020Z in 2002), and concluded that 5Mpix Basic would do quite well enough for most of my photography, still providing excellent screen images at 1280x1024. Since then I've realised that I'll often want to crop, for printing or detailed viewing, so I'm currently on 7Mp 'Standard'. But lens quality is just as important as pixel density, I now realise.

This is a nuisance in terms of volume of computer storage. (I've had to buy progressively larger external USB drives on which to put the data.) This is a minor problem compared with the extra time & battery energy taken writing to disk. The Z712 feels very fast at 5Mp 'Basic' compression, but alarmingly slow at7Mpix, 'standard', let alone 'fine'. Taking huge numbers of shots and throwing most of them away is the most reliable method of getting winners, I have found (and learnt from high-charging professionals, even in the days of film!).

So compromises have to be made, as usual.

Happy shooting,
Alan T

[ac.smith]

Alan T wrote:

The Z712 feels very fast at 5Mp 'Basic' compression, but alarmingly slow at7Mpix, 'standard', let alone 'fine'.

I have inferred from another spec. that Kodak did notchange the buffer size between the 612/712/812 even though some early reports on the Z712 suggested that Kodak was using a new CPU compared to the Z612. The spec. I'm looking at is the number images recorded in burst mode. The Z612 records 8 images,the Z712 does 6, the Z812 does 5 and the Z1012 does 3. As the image size has gone up the number of images captured in a burst has gone down.

[mtclimber]

AC and Alan-

We all have been in this photo game long enough to know that there will probably never be the so called, "perfect camera." Therefore when we make a camera purchase decision, we are sort of signing on the dotted line that we agree to the compromises necessary to get good photos from any particular camera.

Yes, the Z-712 is a bit slow to write and save when set to the 7mp Fine mode, but I accept that because I like the camera (now under $(US) 200.00) and its photo output.

Have a great day.

Sarah Joyce