[IanHoughton]

Its probably cause I'm a tight wad but I bought some Hoya close up dioptres a few months ago +1, +2 & +4 sizes. Was trying to do some close up work but some of the images came out like the one below (as in the blue halo effect when magnified)

I had my 55-200 lens at about 200mm with both the +1 & +2 dioptres attached. What could be causing this effect ?? The picture of the wet leaf in my other thread came out ok with just the +2 attached.

p.s I know I would get better shots with a dedicated macro lens but the budget (wife) won't allow it at the moment.

[Dabhand16]

The blue outline is chromatic abboration (bet I've spelt that wrong) and is often found at the borders of high contrast areas, typically where you get trees against pale sky. Some lenses are worse than others in producing this effect, although I believe that even the aparture setting will also have a bearing on if or how much the effect is apparent.

In this example, I think it is probably caused by the quality of the extra glass in front of the lens, but it might be worth playing around with different settings to see if there is a level that you can live with.

[Soupdragon]

It's got an E in it where the O is.

Asides that, I'll go along with what you're saying.

[Markulous]

CA + lens softness

I get CA when at extremes on my 18-55mm kit lens (unsurprisingly!), mainly in the corners @18mm. CS2 has a fairly good adjustment filter.