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Old 27-06-2021, 08:36 PM
SB (Chris)
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Chromatic aberration on camera lenses

Hi All,
As an experiment for a travel Astro kit I tested both my EFS lenses connected to my ASI183 mc. Was surprised and disappointed to see chromatic aberration in the stars. In the same image the Carina nebula (by contrast) showed very good clarity and definition in its structure.

I looked at some other photographers images who used 85mm prime lens and saw the same chromatic distortion/ colour fringing.

Is a much higher degree of chromatic aberration found in all camera lenses compared to a good APO?

Thanks

Chris
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Old 27-06-2021, 10:08 PM
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Peter Ward
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Sadly it is rather hit an miss in finding a camera lens for astrophotography
with minimal coma and no CA.

I did this write-up a while back on the subject.

APO scopes often have excellent CA but unless they have a dedicated field flattener you may find the off-axis result is not what you hoped for.

The William Optics Redcat/SpaceCat series of lenses are however beautifully corrected across the entire frame of a 35mm but while very impressive for sharpness, they are a little on the slow side as F-numbers go.

Interestingly the likes of Canon are lifting their game with their EOS-R series lenses...not cheap, but their new designs show great promise.

Last edited by Peter Ward; 28-06-2021 at 06:40 AM.
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Old 28-06-2021, 07:02 AM
AdamJL
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Chromatic aberration is common. Also very easily fixed in Photoshop
I’ve got a bunch of Ls that I haven’t tested fully but I’m getting decent results from the 100mm Macro.
The Samsung/Rokinon 135 f/2 is supposed to be incredible
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Old 28-06-2021, 09:23 AM
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Retrograde (Pete)
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Quote:
Originally Posted by AdamJL View Post
The Samsung/Rokinon 135 f/2 is supposed to be incredible
I'm extremely happy with my Samyang. I generally run it stopped down slightly to f2.8 which is of course still very fast by telescope standards.
You can see my latest effort with it here (no CA needing fixed in post): https://www.iceinspace.com.au/forum/...d.php?t=191984

Samyang/Rokinon have pretty much their name by providing excellent nightscape/astro lenses at very modest prices (the catch being that their QC is sometimes less than optimal). There are some other notable lenses that do well at astro like the Pentax 6x7 300mm ED, Zeiss Sonnar 135 & some of the new 85mm f1.4 variants (alongside with the aforementioned Canon L-series).
Most normal lenses are designed for a range of applications and do pretty poorly at astro but there are quite a few good options these days.
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Old 28-06-2021, 09:32 AM
SB (Chris)
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Many thanks for feedback,
Here are the images relating to my initial post below - 70mm and 20mm (Palm tree in foreground).

My editor doesn't get rid of the CA. Haven't tried PS.

Chris.
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Old 28-06-2021, 10:40 AM
JA
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Quote:
Originally Posted by SB View Post
Many thanks for feedback,
Here are the images relating to my initial post below - 70mm and 20mm (Palm tree in foreground).
Chris.
Hi Chris
It looks like there's some coma mixed in with the chromatic aberration, which unfortunately only makes it stand out more. Perhaps you could try to stop down the lens somewhat to reduce the coma (and possibly the CA).

Quote:
Originally Posted by SB View Post
My editor doesn't get rid of the CA. Haven't tried PS
In Photoshop go to Filter>Camera Raw Filter>Lens Correction Icon > then adjust fringing amount and fringing colour (whilst closely zoomed in to an area of fringing to verify this live) - It may help.

Also if you shoot it on camera/DSLR then PS "should" recognise* the lens/camera combination and perform lens correction for vignetting and CA(if you select it to do so in the Camera Raw filter). Additionally wideangle lenses tend to have more difficulty with CA and at the image scale of the 183 will be more revealing than the larger sensor the EFS lens was designed for, possibly even despite accessing a smaller image circle of the lens.

Best
JA

*If the lens/camera is supported

Last edited by JA; 28-06-2021 at 11:07 AM.
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