resizing images help

[raymo]

I don't fully understand resizing in PS. Why do some of my images downsized for posting here although being close to the 200 max look like c--p, too small
and close to pixelated, and others look like perfect copies of the original
large file. I got an Eta Carina image last night that looks really nice as a
large TIFF file, but looks like c--p when downsized. Any help would be
appreciated.
raymo

[Ryderscope (Rodney)]

The only thing I can think of Raymo is if you are starting off from different resolutions maybe? Also, there is an option in JPEG to adjust the quality (1 - 100%) so maybe check to be sure that is not changing.

[RickS (Rick)]

Some images just compress better than others. Read up on Information Theory if you're keen to understand why Images with lots of fine detail will suffer most.

If you have an image that compresses badly you can always downsize it a little further before compressing it. That will give you a smaller image but with less obvious compression artifacts.

The ultimate solution is to include a link to a high res version of your image on an external site as well as the horribly compressed attachment.

Cheers,
Rick.

[billdan (Bill)]

What I do is reduce the size of my image from 4400x3000 to 1024x700 and then save as a JPG with the quality set to about 70% and this usually gets it down to below 200Kb.

[glend (Glen)]

Your never going to get large TIF quality from a jpg, we have to accept that when we down size. Downsizing for Astrobin (who only accepts jpgs as well) is different in that they can accept larger (megabit) jpgs. To get to ISS size limits you need to use the resize box details as stated in the previous post. I keep the quality as high as possible and reduce the size box to about 50%, that usually gets me into the range where IIS will accept it. However, you can post files up to say 800meg to IIS and it will downsize them itself (but I am not sure what it does to quality).

Sharing a higher quality image can be achieved by simply putting up a link to the big file that you might have in your Astrobin Gallery, and posting a small resized jpg there on IIS so people can see what your talking about. If they are interested they will follow the Astrobin link. There are also various Cloud based full sized file sharing sites available if your willing to pay for them. Astrobin also has started charging this year ($36) but does provide a small number of images for free (10 I think).

[Ryderscope (Rodney)]

Originally Posted by glend

Downsizing for Astrobin (who only accepts jpgs as well).

Just a quick note Glen in that I upload my images to Astrobin in *.png format.

[billdan (Bill)]

What would be good is that IIS have a large file database, I would be happy to pay Iceman $40 per year to hold our large files and this way everything is kept in house.

Cheers
Bill

[raymo]

Thank you all for your information. Using it, I have just managed to get my downsized Eta from last night presentable for posting, which I have just done.
raymo

[glend (Glen)]

Originally Posted by Ryderscope

Just a quick note Glen in that I upload my images to Astrobin in *.png format.

Copy that, I did know just forgot because I have been using jpgs there.