What's Caused This?

[Former FLL Now MSP Diver]

Can anyone tell me what's caused the problems with this uploaded picture? You can see where the white washed out areas have appeared on the divers face, and on parts of the turtle, especially the front fin. There's also some orange and red in the seafans at the bottom that looks funky.

The original does not have the same problem. It only seems to have appeared after I uploaded the picture here. This is a copy of the picture I attached to another message here on the board.

Thanks

Marc

 

[Spectre]

From what I've seen... it's a result of jpg compression... To get the image small enough to be postable, it has to be dumbed down some. The bigger the photo is, the worst it might become. It will also happen if you save it in an 'optimized' jpg format, and then save it again [after reducing or something].

I've found that saving things 500x400 or there abouts is usually a decent size for the picture to stay 'clear' after conversions.

 

[Grajan]

A couple of questions:

1. What file format was the original in?

2. What changes did you make?

3. What Application did you save it as a jpg in?

4. Did you control the jpg compression settings?

I just did a test of a similarily complex image and a low compression jpg of an 800 x 600 image was about twice as big as your file suggesting that you have applied too much compression. A 'low quality' ie. highly compressed jpg. will produce this effect.

The other problem that can cause this is multiple edits and resaves on a jpg file. This is a lossy format. every time it is resaved some information is lost for good.

The way I deal with this is as follows:

1. My camera creates high res jpg's.

2. I always resave them as TIF's or PSD's (you can automate this with Photoshop)

3. I do all my editing on the tif. When I am completely happy with the image I size a copy appropriately for the purpose intended and save it as a high quality jpg.

4. I always work away from the tif - never reuse the jpg.

Hope this all makes sense....

 

[Grajan]

Making the postable image smaller allows you to post higher quality images without them getting too large.