jpg compression artifacts

[Robby]

Just wondering what these are and how to recognize them
without a microscope ........

http://www.jetphotos.net/viewreject_b.php?id=1156841

right now I would not know where and what to look for and
last but not least how to correct ....

All help appreciated !

Robby

[Billsville]

G'day Robby,

Compression does not always show up as blocks as is normally seen.

Sometimes it looks like noise, or sometimes it looks like a 'loss' of resolution. In the pic you've linked to, you can see it in three areas of the pic. The grass in front of the plane, the plane itself, and the ocean behind. There is a definite loss of resolution in these areas, mainly in the colour part of the picture. Maybe this happened at the original shot because of the detail in these areas, maybe it happened in the post processing.

Notice the lines on the strip, the windows, and the sharper edges of the plane all lacking a bit of definition? This is usually caused by compression loss as well.

Hope this helps
Steve Brown

[wwshack]

The quality of the blue on the upper fuselage does it for me.
Have you used Neat Image on the photo?
It is a real bummer when a treasured photo does not make it, sorry.

[Greg Wilson]

You need to look at a couple of your camera settings.....................and working from the original will obviously give better results

[Robby]

Thanks for pointing the areas Steve ... I have not used Neat Image Walace ...
I shoot at the highest resolution possible with the E500 in order to have enough 'meat'
left in case I need to crop and reduce to 1024 x 7xx ... one of the other pics of the
same date send in got that jpg rejection .... so I am assuming that it was not a camera setting but some weird thing I possibly did in the postprocessing ... I will try
and redo from the original and see if that helps.

[Billsville]

Robby,

Don't confuse resolution with Compression. Two different beasts.

You can shoot at the highest resolution and have a high compression ratio and the pic will come out looking bad.

Likewise you can have a lower resolution, but have a lower compression ratio and it will look better than the higher resolution picture.

Compression is what happens to the picture when it is being saved to a file on your card in the camera. Higher res, more information to save, more info to compress. Thats why we always say keep your compression levels set to the best quality you possibly can.

Hope this helps
Steve Brown

[Robby]

Sory for my babylonian mixup Steve ... I had the camera (e500) set to SHQ which
is super high quality ... and not to the highest resolution ... while checking the original I did come to the conclusion that I should just try and get that shot again and not spent more time editing ! ... Shooting is more fun anyway !!

Thanks again Steve for a clear explanation !