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Halo after re-size and after sharpen.

MikeTheMason 13 8 1
1 Nov 2009 5:57PM

When I re-size an image in Photoshop CS3 (e.g. down from around 2000 pixels on longest side to 800) I get a halo around the image which is made worse when I sharpen with Unsharp Mask.

I didn't notice this before as I wasn't re-sizing to view on my PC which led to loss of sharpness. Solved that by re-sizing but now have halo problem instead.

Any thoughts? I know there are other ways to sharpen than Unsharp Mask which I need to get into (but kept simple) but it's the re-size halo which is particularly bugging me at the moment.

I have tried various things in Ps and looked on this site and Google but have reached a point of confusion. Re-sizing with Nearest Neighbour seems to give less of a halo but the image quality suffers so Iím using Bicubic Sharpener which is supposed to be best for reduction but gives the worst halo but better overall image quality. Iím on Windows XP and generally do everything with jpegs but have the same problem saving as tiff without compression then making adjustments. Suggestions please.
Hugeknot 17 1.2k 2 Iceland
1 Nov 2009 6:23PM
the halo is mostly due to over sharpening and is difficult to control with the unsharp mask. I would suggest either creating a duplicate layer and masking out the halos, or better still using a different sharpening technique.

There are some good actions out there that let you control the halo effect. A couple of these actions can be downloaded from here.

I use the smart sharpen function with a duplicate layer and mask see here.
lemmy 15 2.9k United Kingdom
1 Nov 2009 6:37PM
Try shooting in RAW, save as tif or psd and resize that.

The halo is due to oversharpening so ease off on your settings. It can be useful to duplicate your image layer, set the layer blend to luminosity and do the sharpening on that.

The trick is to shoot in RAW. If you shoot jpg and sharpen, you are sharpening an image that has already been sharpened.

And remember that it doesn't follow that all images need sharpening so don't do it unless you really need to.
cameracat 19 8.6k 61 Norfolk Island
1 Nov 2009 6:56PM

Quote:and generally do everything with jpegs

First up, How have you set your camera up...?

By that I mean do you have in camera sharpening " On " and if so what level of sharpening is it applying...?

If you have sharpening on in the camera, There is really no need to apply high levels of sharpen in software, Or you get oversharpen, Which looks worse than none at all.

Quote:duplicate layer and masking out the halos

Whilst that might help, Whats the point of oversharpening something, Then having to mess around in layers to correct it, All your doing is creating work, Your also mangling the data files even further, The more you mangle the worse it gets....Sad

If your really intent on doing a lot of post processing, You should really consider working with " Raw Data " ie: Shoot raw.

Raw or Tiff are the only formats that can be messed around with Add infinitum, With little or no loss in quality.

The same can't be said for " JPEGS " especially if you have all the onboard processing doing its thing, Every time you open or close a Jpeg file, It degrades the image, Same happens when its pulled around by lots of post process procedures.

Bottom line, Unless you intend printing directly from the camera, Turn the onboard sharpening option to off.

Only add sharpening as required, Once you have finished all other processing work, It should be the last thing you do.

If you downsize an image, It may need a very smal amount of sharpen, Over and above the basic level applied to the original full size version......!!!!
BernieS 14 243 United Kingdom
1 Nov 2009 7:03PM
As already said - shoot in RAW and do your post-pro in 16bit TIFF. Only convert to JPEG at the final stage, and then use the minimum amount of compression that you can get away with - 10 is usually a good compromise between quality & file size.

Remember that every time you save a JPEG, it slightly degrades the image.
1 Nov 2009 7:55PM
What sort of file are you inputting to Photoshop in the first place? If you're downsizing from 2000px, your files aren't big to begin with. And you don't need to shoot in RAW either. (That should draw a few comments!) A JPEG at Normal setting in-camera ie, very little in-camera sharpening is, as Cameracat stated, what you should be using. Little or no sharpening in-camera. Do your processing, save for web, I save my uploads into a desktop folder, after "save for web", if you think it needs sharpened take it back into Photoshop and sharpen it, then upload.
MikeTheMason 13 8 1
1 Nov 2009 10:36PM
Hello everyone, thank you for the replies - a lot to go through, probably after work tomorrow (have just got back in - haven't been ignoring you).

First up I've got a Canon 400D and can't find anything in the menus about sharpening so I'm assuming in camera isn't an option.

I use Unsharp Mask because it's easy for a novice but I really only do what is necessary and am doing it at 100% view. Smart Sharpen could be a way forward when I've got my head around it.

I've tried shooting in RAW but when I'm after birds or bugs I get around eight frames continuous shooting then the camera takes a break to save to my card (Sandisk Extreme III 4GB CF) and I draw stares with my swearing. Plus the pics I'm working on at the moment were taken on holiday when storage was an issue even with an Epson 40GB store and save.

The halo effect is more obvious when I resize and sharpen but I also get it when I only resize (assuming with my 400D there is no sharpening going on in camera). The resize halo is what I don't understand. For the purposes of trying to work out what is going on all I'm doing is opening in PS (picture of a Pelican against a blue sky) cropping and resizing from 2154 to 800 so I can view the picture full size in Windows and there is a deffinate halo.

Just been trying with opening a jpeg as camera Raw, resizing and saving as a TIF file and still get a halo.
mark_delta 15 1.3k
1 Nov 2009 11:24PM
Just download what the press on PC use ... irfan view
it performs all basic necessary adjustments without the bloatware, quickly first time every time.
RogBrown 16 3.1k 10 England
2 Nov 2009 12:30AM
Try Easy Thumbnails - free download. Easy peasy!
Tooth 17 5.8k 227 Ireland
2 Nov 2009 1:09AM
Just a quick rule of thumb which may be part of your problem. Thelevel of sharpening required (say percentage in unsharp mask) is dependent on the size of the image you're sharpening. So if you have an originsl pic at say 3,000 pixels wide, 90% sharpening may be spoyt on. BUT, if you then resize to say 500 pix wide, then that level of sharpening is bound to produce an oversharpening effect (especially as you're effectively sharpening something that's already been sharpened.

So, before you rush to find another method instead of unsharp mask, first just try bearing this in mind and try the final sharpening of the small file at, say, no more than 30%, and see the difference

Chrism8 16 1.0k 32 England
2 Nov 2009 8:13AM

Quote:Just been trying with opening a jpeg as camera Raw, resizing and saving as a TIF file and still get a halo.

My advice would be to shoot in the largest file size available i.e Raw then save as Tiff ( non Lossey ) then convert to jpeg as required.

You wont have gained anything by going from an original jpeg to a raw then to a tiff file.

digicammad 19 22.0k 40 United Kingdom
2 Nov 2009 8:32AM

Quote:'ve tried shooting in RAW but when I'm after birds or bugs I get around eight frames continuous shooting

It won't solve your sharpening problem but try being more selective with your shooting. There is no real need for you to shoot more than 3-4 frames in a single burst.

As to the sharpening, I would recommend you look up the 'high pass filter' method. This is very easy to use and you have to really abuse it to get halos. There is a technique article on here which I wrote a few years ago.

Have fun

John_Frid 16 514 57 United Kingdom
2 Nov 2009 1:32PM
You can indeed set sharpening in camera on the 400D.

The 400D has a simple range of seven steps, with 0 being no sharpening and 7 the maximum. The default level Canon sets varies according to the particular 'picture style' image parameter group chosen. Standard and Black&White is level 3, Landscape is level 4, Portrait is level 2, whilst Neutral and Faithful are level 0.

My recommendation is to shoot using either the Neutral or Faithful styles and do anysharpening needed in post processing.

The best advice I got on sharpening was to make it the very last thing you do. So don't sharpen until you have resized. When you sharpen for the web, view the iamge at actual size - this lets you see exactly what the effect will be. When sharpening fro print, it is often better to view at 50% size.

There are a variety of ways to sharpen an image, and different ways will suit different images. One of my favourites for images on the web is to use the High Pass filter (using soft light blending mode) as this is s little less harsh and rarely causes halos.

Hope that helps.

newfocus 16 647 2 United Kingdom
2 Nov 2009 2:02PM
Everyone seems to develop their own style and techniques but a quick step by step summary of what works for me from camera to web is:

- turn off all in-camera sharpening
- work in raw/16 bit and don't sharpen at all during processing (including turning off sharpening in whatever raw converter you use)
- do whatever adjustments you want do
- flatten the image
- downsize for the web
- duplicate the flattened layer and sharpen to taste (around 0.3 and 100% as a starting point but it depends on the image)
- Mask any areas of very high contrast as hugeknot suggests above - it's near impossible to get them halo free otherwise at web sizes
- convert to sRGB if you're not using that already
- use the save for web option

I hope that helps a little.

lemmy 15 2.9k United Kingdom
2 Nov 2009 3:21PM
It couldn't be chromatic aberrations you are seeing could it? These are colour 'shadows' at high contrast edges on an image. The bird/ sky transition would be a likely location for such CAs.

Since it is a product of the lens, CA would be visible in RAW or jpg originals and would be exacerbated by down-sampling.

Does it occur with all your lenses? Zooms, especially wide angle and wide range ones are especially prone to it. If this is it, it'as easily enough removed.

There's a graphic example Here

Just a thought.

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