Hey everyone,
I just got a 20D off craigslist and was excited to finally have a use for my EOS lenses that didn't involve #####ing about how there aren't any good labs anymore. Anyway, I'm having problems taking shots of a couple of birdsnests in my tank. The white tips are 'glowing' in the image. The one below is underexposed by 1 1/3 stops. I'm wondering if this is an artifact because my frags are so tiny or a correctable issue.



thanks!
-a

your sensor can only capture a certain number of stops of dynamic range. this scene exceeds that (as evidenced by the blown highlights). your only real option in this situation is to underexpose even further until you start to lose contrast in the shadows and then try and bring the exposure back up in post processing. i guess you could also turn down the light a bit if that's an option (kill a bulb or two if you've got a milti-bulb setup)


also, what lens are you using? you've got some weird haloing going on that I've only seen in canon's DO lenses.

EF 85mm/1.8, but I have a UV filter (ie lens protector) on there. I haven't tried pulling it off. The lens isn't a DO lens.

I can try axing some of the light, I actually do have that option.

Take the uv filter off, but that is chromatic abberation .

yeah, that's probably going to be your best bet.

i'm guessing that the haloing is just bleedover on the sensor from the super super blown highlights.

in theory, the UV filter shouldn't degrade your image quality (if you've got a decent one), but people will argue all day about that!


not entirely sure that is CA. i'm leaning towards not.

I'll try taking the UV filter off and killing different combos of bulbs when I get home, I'll post the results here.

I would be extremely disappointed if it were chromatic aberration, I feel like that's a pretty damn good lens. I really appreciate the link.

the 85 1.8 Suffers badly with CA at wide open shooting..With a halide or some serious bright light on it does not surprise me you got this CA issue

what aperature were you shooting at? If you weren't already try stopping down as much as you can to see if you can sharpen up that wierd halo effect. Depending on which lens you are using I'd shoot for at least f/11. Plus depth of field is always an issue with macro shots anyway.

Ding! You guys are both right. All shots without the UV filter, -1 2/3


f1.8

f2.0

f2.2

f2.8

f3.5

f5.6

OK - another related question for all of you.

Of the 60mm EF-S macro and the 100mm EF macro, which suffers less from this effect? Anyone have both to do a comparison?

thanks!
-a

I haven't experienced any ca with the 100mm. What you posted was a really nasty example, but most photo editing software can get rid of it nicely.

Zero ca with my 100mm.

is f 5.6 the most you can stop down with that particular lens?

Nope, I can go to 22. I didn't because it was all handheld and I was at 1/40th @ f5.6.

ISO?


as a side note, that's some of the worst CA i've ever seen! eek!

neither Macro should have any issues with CA..I use to have the 85 1.8 it was nice but that CA wide open in high contrast areas was a killer sometimes
Also ditch the UV filter. I think they do more harm then good and the lens was not designed with it there so adding it changes its optical property

fo-hundy

and, I know. It sucks. I'm going to see if there's anyone that'll trade me the 60 or 100 macro for it or it plus $100 (for the 100). it's in perfect shape and i love the big aperture, but, well, not with that problem so much.

To be fair, that's pretty much the contrastiest (if that's a word) you can get. new bone and flat black with tons of light on the bone.

dont toss the lens just yet..I mean how often are you going to shoot WIDE open in a situation like that. It is bad CA mine usually vanished almost totally at around 2.2...You could send it to canon and they could calibrate it.

Really? I didn't know that. I'll look into that, thanks.

if its under warranty..They will adjust it for free

still looks flipping awesome