RichC
Well-known
I usually post images that are about 800 x 600 pixels, occasionally a bit larger if there's a good reason, sometimes smaller if I want to save space and bandwith.barjohn said:As for quality, I took the original shots and scaled them down to either 1100x600 or 800x600 ... I also think I set quality of the JPEG to low to keep the file sizes small. What is the recommended method for posting?
The issue with your JPG images (ignoring the strange interference pattern) is that you've set the quality setting ("compression ratio") too low when you're saving your JPGs. A good compromise is 80 (= high) - that's what I usually use for attachments, etc. If I'm putting photos in a gallery and want the best quality, I use a setting of 10 (= maximum).
Lastly, all my processed, full-size images have been sharpened and saved as TIFs (don't save your master images as JPGs*). However, when they're reduced they go a bit furry, so I always sharpen my reduced images slightly.
The above is exactly what I did with the three attached photos I posted earlier: reduced to 900 pixels max height/width, quality = 80 plus sharpened slightly.
For small images in posts, etc., I don't bother to open Photoshop (too much effort!). Instead, I use any cheap and cheerful image processor to hand. For the three aforementioned photos I used IrfanView (free and fast - just Google!), and I think the quality of the attached photos is fine for web viewing.
[* The JPG format deletes pixels in order to create small files. The lower the quality, the more pixels are deleted. When a JPG file is opened, an embedded routine attempts to guess the position and colour of the deleted pixels. Thus, even high-quality JPGs are slightly degraded compared with TIF files (which never change), though the difference is minimal for JPGs saved at the high-quality setting. Another reason for using TIFs as your master files is that not exactly the same pixels are deleted each time you resave a JPG (compounded if you've altered the image before resaving), so some pixels that are guesses are treated as original image pixels and kept - keep resaving a JPG, and this compound error will reduce image quality visibly. Low-quailty/degraded JPGs thus show loss of detail - which is seen in two main ways: blurring of detail and pixellation ("JPG artifacts").]