Camera lens - star bloat/halo issue

[Crunchard]

I use a mixture of camera lenses for wide-field (and slightly more narrow field) and am having fun and games with star bloat and purple halos.

My 50mm F2 Yashinon exhibits almost no star bloat, and yet my 28mm F2, Carl Zeiss 135mm F3.5, and unbranded 200mm F4 show it quite bad. I normally runs these at least one stop down (sometimes more). All these lenses are older lenses with the M42 connection+EOS adapter.

My camera is a modded Canon 1100D - note the filter has been replaced with a Badder, and not removed entirely.

I've tried a few varying settings, shorter exposure, smaller aperture, but the ISO tends to remain around the 800 (1600 on occasions) setting.

My post-processing skills are pretty average to say the least, so removal that way is a pain for me - despite trying to understand the various online tutorials, etc.

Any advise?

Would a CLS filter help?

Almost at the point of stopping use of the longer focal length lenses.

Thanks

[steppenwolf]

Could you post up a typical sample image for us to analyse?

[Crunchard]

I've cropped this one to show the problem, also looks like my focus was a bit off on this too.

[JB80]

I generally run my 300mm zoom lens at F/8 or 9 and it still has similar bloat and chromatic aberration, stopping it down further does help a bit but it's always still there for me.

[JohnC64]

Hi Crunchard,

focusing on these fast lenses is very hard to get spot on.  Take a look at the micro focusers for camera lenses at Teleskop express  http://www.teleskop-express.de/shop/product_info.php/info/p3285_Microfocuser-and-focus-lock-fuer-camera-lenses-up-to-D-75mm.html

Hope that helps
John

[Crunchard]

Thanks John - those look really a good idea!

[Crunchard]

Thanks Jarrod - I have tried stopping down, and, like you, still suffer. I need to test a decent Canon L lens to see if that still suffers really, then I will know if it is just glass related.

[steppenwolf]

The chromatic aberration in your sample image doesn't look that bad to be honest but blue halos are sadly all to common with camera lenses. Stopping down the lens at least 1 and preferably 2 stops helps with image quality but at the cost of severe diffraction spikes from the leaves of the iris although an aperture mask will help here. The halos can be removed in post processing but if this is not your 'thing' then I'd try making an aperture mask as this will help a bit but will not completely resolve the issue. To determine the 'hole' size of your mask, decide what aperture you want, say, F6.3 for your Carl Zeiss and divide this into the focal length (135mm) which gives a figure of 21.4 so your mask's hole size should be 21.42mm in diameter.

As others have pointed out, your focus is a little soft in this image but that is something you can resolve and those micro-focusers are a great idea.

[Crunchard]

Thanks Steve, I am going to persevere with the 135 and 200mm lenses for now, but will probably look to get a small APO at some point (TS seem to do some nice 50/70 and 80mm APO's which I hope will control affects like this better).

[Merlin66]

Have you considered a Minus UV filter? This usually supresses the "blue" halos....

[Alien 13]

Have you considered a Minus UV filter? This usually supresses the "blue" halos....

Whats a Minus UV filter and how does it differ from a normal UV Filter.

[Merlin66]

Similar.

Photographic filters are usually "Minus Violet" rather than the astronomical "UV-IR" blocking........

Found this site...may be of interest...

http://www.lenstip.com/113.1-article-UV_filters_test.html

[Crunchard]

It would be interesting to see how I could connect a violet cut filer to the front of my 4 different camera lenses - as it would involve step up / step down filter connectors of some sort.

[Alien 13]

It would be interesting to see how I could connect a violet cut filer to the front of my 4 different camera lenses - as it would involve step up / step down filter connectors of some sort.

I use the step up ring sets off e-bay the UV filter is chosen to be the largest size of my various lenses then the smaller ones steped up to fit, i then have in my case a 58-72 lens hood on the end.

[Davey-T]

Thanks Jarrod - I have tried stopping down, and, like you, still suffer. I need to test a decent Canon L lens to see if that still suffers really, then I will know if it is just glass related.

I have Canon 200 L and still get haloes.

Dave

[Crunchard]

Thanks Dave ... I won't part with the few hundred quid as a test then

[Crunchard]

I use the step up ring sets off e-bay the UV filter is chosen to be the largest size of my various lenses then the smaller ones steped up to fit, i then have in my case a 58-72 lens hood on the end.

Cheers, will take a look at those.