Does CA look like this?

[Planapo]

This is one from my first attempts with an objective (CZJ "aus Jena" Planachromat 10/0,25 160/-) on bellows, stacked with CZM. It's not a photo that worked out very well. From the single frames I didn't realize that the lighting was to harsh for my taste when shooting. But the sculpturation/"wrinkles" of this Myrmica are quite impressive, perhaps I should give this specimen another go. (At the moment most of my gear is safely packed away because of some building work going on in the house, and I don't want fine gypsum or cement dust on my equipment.)

Anyway, I post this one because I'd like to know what you think of the performance of the objective. To me it seems like it falls off towards the edges but the center looks not too bad. Would you say that this objective suffers from CA?

--Betty

[rjlittlefield]

I agree with your assessment: good center, not so good at the edges, obvious CA as evidenced by color fringes at the lower right corner.

You can get rid of the color fringes, or most of them anyway, by using PTlens or some similar plugin or tool in Photoshop. But "under the covers", the CA will still be causing some radial smearing within in each band (R,G,B), even if the bands are then corrected to line up with each other. Remember our discussion HERE and in the surrounding thread.

That said, for most images it is central resolution that matters. Different people have different sensitivities. I am very sensitive to color fringes; they drive me a little crazy. Get rid of the fringes, and I'm not bothered by a little loss of corner resolution.

--Rik

[Planapo]

Thanks for your evaluation, Rik.
I did think of your lacewing egg picture from back then where I can see the colour fringes much more clearly. Here with this ant head I rather just see that it's not right sharp at the edges, so that first I had thought it was due to some vibration in my set-up, but then saw that the center looks much better. And as this objective is probably meant to be used with the same compensating eye pieces as the one you initially used, I thought of CA.

Funny thing that back then when marveling at your lacewing egg, I would have been delighted, if I had been able to achieve a photo like this, but now that we know of better "glass" (thanks to Charlie) I won't even think of using this objective to shoot a couple of dozen frames for a laborious stack again. Sic transit gloria mundi!

--Betty