Loss of quality when posting?

lynn53

New member
Isn't it true that after you resize a photo from a large of 10.M to a posting size of 50k's that the quality of that photo is not nearly the same.? The other day I was kinda proud of a pic I took with my macro lens and it looked pretty good on my screen...then I resized it...then I realized that it wasn't near the print that it orginally was.
I guess there is just no getting around this...right?
 

jeffbrig

Premium Member
jpg is, by definition, a lossy compression algorithm. You'll always lose quality when you resize and compress. Also, some photo editors have better interpolation algorithms when you resize. For example, a resize done in photoshop is 10x cleaner than one done in MS Paint. I also really like photoshop's "save for web" option, because it lets you previous the image at various compression levels, and trade off file size for quality.
 

maroun.c

New member
That is right, at least that's why you pay for a 10 MP camera and not a simple 1 Mp.
Try to crop your picture so that what yo ukeep and resize is the essential part you want to show (that is with taking care of the composition you want)
However resizing your picture to something around 1000x750 for a horizontal shot. Apply a mild unsharp mask as the effect of unsharp mask is more evident on smaller size images (typical values would be 300-0.2-0 or 90-0.5-5) then Select save as and decrease your resolution till your picture is of a good size for posting (somewhere in between 100 and 300 KB depoending on the hosting site)
On the good side compressing an image sometime helops hide little blurr. also screens have a maximum resolution of 72ppiwhere as a picture for printing is printed at a resolution of 300ppi. a 1000 pixels wide image will usually occupy the whole width of the screen (this is what you see when you click on fit to screen) So basically resizing an image to 1000 pixel wide and down to 72 ppi will not really destroy an image. Worst effect will be loss of resolution. then your image gets destroyed when you lower it's quality by increasing the compression to minimize the file size.
 

lynn53

New member
thanks both of you, I'm a little confused here though...as when I "save it to web" to resize it I have to basically put the JPG quality slider to 0 or 1 ...or I can't get it down to the 50kb that this site allows. I'm already cropping and dropping the pixel size to 650 at the max. Would I be better off to drop the pixel size to ...say 350 max and then up the JPG quality?

thanks again
 

jeffbrig

Premium Member
I resize the pics I post here to 600 pixels wide and my default jpeg compression slider is set to 50 in photoshop. That gets me pictures anywhere from 30kB if it's an isolated tank shot, or maybe 75kB for a shot with a lot of detail. My RC gallery has long been filled with old pictures, so I host offsite these days.

Here's an example of a 600 wide shot that's 48kB.
bubble_tips_8_14_06.jpg
 
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