Uploading jpg files

Nonno · #1 03-26-2010, 03:46 PM

After some discussion here
http://www.wetcanvas.com/forums/showthread.php?t=613627
about fuzzy uploads I did a simple experiment.
Here are 4 uploads of the same file, a red circle on a white background.

The attachment at the bottom is a BMP which does not modify the file in any way. You get pixel for pixel exaxtly what is saved. I couldn't upload this in the normal way so it is an attachment. It's size is 29.3k

The second is the same file, saved as a JPG with a compression of 7.
The third is saved with a compression of 15, and the last has a compression of 30.
You may not see any difference between them on your monitor, but save them and then zoom in with photoshop or whatever image program you use and you will see it!
Note the degredation gets worse as the compression depth goes up.
As you can see, this degredation is a trade off with final file size.
So, it's best to use as small a compression as you can to keep best jpg image quality.

Also if you are working on an image, to keep best quality, don't save it as a jpg until the final image is produced, and even then keep an archive version as a bmp or other non compressed format.

This is particularly relevant for those posting line drawings, as high jpg compressions affect lines quite a lot!

Jonathan.

jpg compression 7 size 3.03k

jpg compression 15 size 2.41k

jpg compression 30 size 1.94k

trevors · #2 03-26-2010, 04:39 PM

Quite right Jonathan well worth reminding everybody though!

Adair_P · #3 03-26-2010, 04:40 PM

Great info..... thank you Nonno. We will have to put this somewhere relating to uploading images where everyone can refer to it.....

LGHumphrey · #4 03-26-2010, 05:01 PM

But for our purposes what's the diff.? I mean, why worry about this?

**bethanyt** · #5 03-26-2010, 08:33 PM

Mr Humphrey, I find this information is helping me in particular. I could not work out why my drawings were not showing clearly- the uploaded drawings were looking more fuzzy than in real life. I need all the help I can get, so I asked the question about getting a clear image uploaded.

Jonathan, thanks again for taking the time to help with my problem! (what do you charge, again?)

roy-p · #6 03-28-2010, 01:51 AM

Thanks for this Jonathan, it'd surely be very helpful. The problem with bmp files is that they tend to become quite large.

LGHumphrey · #7 03-28-2010, 02:55 PM

Hi Bethany, proof of the pudding's in the eating, they say--I can't see any difference in those four red rings so will be interested to know if your drawings really do load up more clearly using bmp. Please keep us informed.

Maybe you could load up one of your sketches in jpg and the same picture in bmp, so we can compare?

Nonno · #8 03-28-2010, 03:52 PM

hi Lawrence,
I can see the difference, but that may be because I know it's there!
Especially on the 30 X compression one, it looks like a dark smear around the circle. To see it more clearly, open it with any photo processing application and zoom it.

You are correct in that for most of the people most of the time this is not an issue, but it does occasionally come up.

It also depends greatly on the actual image as to whether this effect is a problem, or even whether it is visible.

Also, we are used to seeing jpg images, so it's the norm.
Does anybody, when using their digital camera or scanner, NOT produce a jpg file as their original starting file? I know that my camera will produce raw files, but I have never tried it! Why? because the file size was bigger than the amount of RAM in the computer I had at the time. My camera will also take photos at 12 Mega pixel resolution but I have always used 6 because the one time I tried 12 the computer couldn't handle that size image.
Habit has kept me doing what I've always done! I must try the larger size again now I've got a better computer.

Jonathan.

lovin art · #9 03-28-2010, 05:16 PM

Quote:

Also, we are used to seeing jpg images, so it's the norm.
Does anybody, when using their digital camera or scanner, NOT produce a jpg file as their original starting file? I know that my camera will produce raw files, but I have never tried it! Why? because the file size was bigger than the amount of RAM in the computer I had at the time. My camera will also take photos at 12 Mega pixel resolution but I have always used 6 because the one time I tried 12 the computer couldn't handle that size image.
Habit has kept me doing what I've always done! I must try the larger size again now I've got a better computer.

Jonathan.

HI Jonathan, Please explain this better to me my buddy

, as Im not sure just what you mean, is it that you mean the bigger the hard drive or ram i get

with those too....and does that mean the more room to handle the picture better, my camera takes 10mega pixs and does that more megapixles make a diff anyway....I tend to compress the file down first instead of resizeing it first....god this is confusing

Nonno · #10 03-28-2010, 10:43 PM

Looks like I'm digging a hole for myself!
let me think about it for a while!

Jonathan.

Nonno · #11 03-29-2010, 08:02 PM

I've just done an internet search on jpg files, and there's lots of stuff available.
Rather than trying to reinvent the wheel on what is rather off topic for here, I suggest that those who are interested do some research themselves.
If anybody wants to ask me any questions then they can PM me.

I'm not an expert on this, just somebody who has had a little experience with problems using jpg images.

Jonathan.

giancarlo80 · #12 03-30-2010, 12:43 AM

Hey Johathan, charles here;
I am among those who don't grasp what you're saying but then again I was never considered the brightest light on the chandelier.
Not familiar with compression sizes nor BMP's
I scan everything and rarely use my 10 mg for reproduction.
Briefly I scan and open in photoshop with 200 resolution and convert the image size to the larger resolution always 800 pixels being the larger size.
Then I save it as a jpg. and WC accepts it.
I thank you for the thread and am always interested in anything that would improve quality. You're a good man Jonathon and I welcome your input.

lovin art · #13 03-30-2010, 01:40 AM

Quote:

I thank you for the thread . You're a good man Jonathon and I welcome your input.

I totaly agree with you Charles.....

**bethanyt** · #14 03-30-2010, 01:56 AM

Thanks again, Jonathan, for the time you took!
I just posted over in portraits using GIMP to resize in jpeg- I can see a big improvement in definition even with me not doing anything else. I will try a drawing on white paper tomorrow (light fading here now)
I am always wanting to learn better ways to do things- in painting and in technology!

LGHumphrey · #15 03-30-2010, 05:47 PM

Ah, so bmp is bitmapping. (Wikipedia) Heard of it--said to be very good.

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