Speckly JPEGs

Mwezzi · 14th April 2008, 5:23pm

I hate them. No matter how I fiddle with the images to try and reduce it, whenever I put a picture on the web I get speckles such as those in the sky in the image above. I've tried smoothing over areas where this is likely to occur but this has relatively little effect. Is there any way to avoid or fix this?

**djtoast** · 14th April 2008, 5:43pm

Shoot at the lowest ISO you can; if you have photoshop try despeckle.

*Edit* - ick, that's 40kb, must be quite harsh JPEG compression, save at a higher quality / filesize!

*Edit2* - looking at the original in your gallery, there are lots of quite detailed little specs of cloud in that area, which will always introduce nasty compression artifacts if you save at to harsh a compression setting. The small screen-res version that the AN gallery automatically creates won't be great quality, you can get a better version yourself by saving at that size (ie pixel dimensions) in photoshop or similar, or by using inline image editors like this one.

At that size (depending a lot) on what the picture actually is of, aim for maybe a file size of 100kb or so if you wanna banish such mottling.

Mwezzi · 14th April 2008, 5:48pm

Quote:

Originally Posted by djtoast

Shoot at the lowest ISO you can; if you have photoshop try despeckle.

*Edit* - ick, that's 40kb, must be quite harsh JPEG compression, save at a higher quality / filesize!

ISO 100 - 80 lost detail. The file size is actually 453KB for the full size in the gallery, that's just what it was scaled it down to in order to fit the post.
As for photoshop... it's being worked on. The despeckle I have on the current programme is worse than useless.

Largest of Gregs · 14th April 2008, 5:49pm

set quality to 100

*Potatojunkie* · 14th April 2008, 6:01pm

Is this an issue with images straight from the camera, or are you only getting this after tinkering with them?

Mwezzi · 14th April 2008, 6:08pm

It seems to happen to the images after they're uploaded to the internet, regardless of tinkering - It's probably related to file resizing thought, I just don't know how to get around that. Some do display a small degree of speckliness straight from the camera, but that's usually an ISO problem I'd say.

*Potatojunkie* · 14th April 2008, 6:29pm

AN's gallery software makes a shitty mess of things when it resizes them. Do it yourself and then save at the highest available quality.

I'd also suggest overexposing a little and then pulling things down in post, but it depends on how capable your software is.

**djtoast** · 14th April 2008, 6:50pm

Is there a "RAW" mode on the camera? You could compare with a JPEG from your camera, seee if it's not doing a great job of compressing them in the first place.

Woolies · 14th April 2008, 7:13pm

Is it the IXUS 75 camera that's causing bother? (from that church pic's exif info, I am not psychic)
(no RAW mode toast)

And did you upload the straight from camera version to the gallery here?

If so it looks from pixel dimensions to be saved at the M2 resolution rather than the cameras highest capable resolution. There's also a risk that you are shooting at "fine" rather than "superfine"? (Although I never really understand exif Compressed Bits Per Pixel...)

Both would involve the camera doing extra maths to the jpeg which it's usually best to minimise.

Make sure the camera is set to Large Superfine and that you don't use a programme mode that may over-rule & lower your settings! I think my wee canon does that for the green box mode at least

Mwezzi · 14th April 2008, 8:11pm

Quote:

Originally Posted by Woolies

Is it the IXUS 75 camera that's causing bother? (from that church pic's exif info, I am not psychic)
(no RAW mode toast)

And did you upload the straight from camera version to the gallery here?

If so it looks from pixel dimensions to be saved at the M2 resolution rather than the cameras highest capable resolution. There's also a risk that you are shooting at "fine" rather than "superfine"? (Although I never really understand exif Compressed Bits Per Pixel...)

Both would involve the camera doing extra maths to the jpeg which it's usually best to minimise.

Make sure the camera is set to Large Superfine and that you don't use a programme mode that may over-rule & lower your settings! I think my wee canon does that for the green box mode at least

Ah, upped the resolution now. Was already on SF, but wasn't aware that the original size would have such an effect. (What are teknolojee?) I'll see how that affects it, thanks!

Woolies · 14th April 2008, 8:18pm

I'm not 100% certain but my brain says that the max resolution is data from all the sensor cell bits, interpolating that down would involve maths.
Although I guess it may be a case of "every second pixel" which I'd assume was just as smooth as full resolution

I'll be chuffed and take full credit if I'm right though

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