[JamesNZ]

Hey all,
I recently bought a second-hand FA 50mm f1.4 off ebay, and I've found that it tends to produce halos around highlights in low-light situations.

For example, this shot was taken with the 50mm (no PP):


And this one with my DA 18-135mm:


What could this be caused by? I've read online that it could be from a dirty filter, but I don't use a filter with this lens, and as far as I can tell it's very clean. In all other situations it works beautifully.

[Ash]

Hi James.
You'll find the FA 50 image overall is not accurately focused and has a significantly lower depth of field.
The DA 18-135 image is sharp all over.
The EXIF data would likely reveal why: the FA 50 image probably has a f/2.8 or below aperture set, whilst the DA 18-135 appears to be f/5.6 or above *just a guess, I can't see the EXIF information on these images).
But the image from the FA 50 is soft all over - the focus may be accurate for the bottom part of that spacecraft, but because of the shallow depth of field (big aperture), nothing outside of that distance from the camera will be in sharp focus.

[dbs]

+1


Agree

[clackers]

I think if you were to stop down to the same aperture as the 18-135, the chromatic aberration would match.

The tinted outlines fast lenses are prone to in these situations can be removed in Lightroom, for instance.

It's usually moving the purple slider to '4' that most often works for me.

[JamesNZ]

Hmm, ok. I see how the focus/aperture is probably to blame in that shot, but what about this one?



That was taken at f1.4 at infinity focus, and there's some noticeable blue halos around the streetlights that I haven't seen before (as opposed to bloom). Or is that normal when it's so stopped up? I haven't used a lens this fast before

[BigMackCam]

Hmm, ok. I see how the focus/aperture is probably to blame in that shot, but what about this one?



That was taken at f1.4 at infinity focus, and there's some noticeable blue halos around the streetlights that I haven't seen before (as opposed to bloom). Or is that normal when it's so stopped up? I haven't used a lens this fast before

Bright light / high contrast areas, photographed with a fast lens wide open, will often result in this kind of halo effect. Indeed, you might also see it when stopped down somewhat and the bright light source is significantly outside the acceptable depth of field...

Note, this isn't specific to your particular lens, but most fast lenses...

[JamesNZ]

Ahhh, I see. That solves that then, thanks everyone for the advice.

[Heebie]

That was taken at f1.4 at infinity focus, and there's some noticeable blue halos around the streetlights that I haven't seen before (as opposed to bloom). Or is that normal when it's so stopped up? I haven't used a lens this fast before

at f1.4, your entire depth-of-field is very narrow. What you're seeing is probably not "haloing" it's probably "bokeh"

Bring that up to f5.6 or f8, adjust your exposure, and see what it looks like.
Pentax f1.4 lenses are really sharp, within the in-focus field, but if the in-focus field is only 3-metres deep in a landscape shot... that'll leave a lot out of focus.

I believe someone suggested basically the same above, and I think that person was correct. That shot was much closer to the lens, so the depth-of-field would be even shallower at a wide-open aperture. That lens at f1.4 in close shots can have a depth-of-field just millimetres or centimetres deep.


Keep shooting with varied settings until you figure out how to get exactly what you want.

[UncleVanya]

The FA 50 F1.4 is very dreamy wide open. It has almost half the resolution of what f2.8 gives. Try stopping down to f2 and 2.8 to see if this gets better.

[Ben-G]

+1 to UncleVaya


Ben-G