Fun with my 50mm lens

[rogerg (Roger)]

G'day all,

Had a good weekend out at the ASWA Tammin site last weekend, where I spent the night playing with different targets throught my Canon 50mm F/1.4 lens. The lens is o easy to focus with! seeing fainter stars really helps in live view.

There's a few photo's here:
http://www.rogergroom.com/items/aswa..._december_2010

including...
- a crop of a northern milky way area having M36, 37 and 38
- orion
- lmc
- southern cross and eta

.. and a couple of startrails, one showing the setup tracking taking the other shots.

Had a great time out there, and am quite happy with the results considering all. Wish I had a modded DSLR to get rid of the DSLR colour problem, get the colour back in Eta and the LMC. Oh well!

Most were shotat F/2.8. While F/1.4 provides amazing exposure detail in short times the lens really distorts and adds a lot of CA fully open where as at F/2.8 it's near perfect, especially with regard to distortion (false colour is still somewhat evident).

Roger.

[multiweb (Marc)]

Great shots Roger. I sarted playing with a Pentax 18-35 (67mm dia) last night and I found a fair bit of coma and field curvature on the edges. Do you stop the lens and make a mask in front? Or do I need to zoom in more. It goes from 18, 25 to 32.Last night I tried 25.

[seeker372011 (Narayan)]

great results,

[rogerg (Roger)]

Originally Posted by multiweb

Great shots Roger. I sarted playing with a Pentax 18-35 (67mm dia) last night and I found a fair bit of coma and field curvature on the edges. Do you stop the lens and make a mask in front? Or do I need to zoom in more. It goes from 18, 25 to 32.Last night I tried 25.

Thanks

I just stop it down in focal ratio, so from F/1.4 to F/2.8 on the camera settings. I don't stop down the actual apperture of the lens, I think that would only make the situation worse but haven't tested it to have proof Stopping the focal ratio to F/2.8 has a dramatic effect on the picture quality, the corners go from swan shaped stars to circular stars, and F/2.8 is still quite fast

Zooming in/out will change the distortions evident from your lens but I think it's a case of trial and error. I've tried different zooms with my 17-40 and 70-200 and find it's not necessarily the long end (40mm and 200mm) that has less distortions, but there's always a best place, if keen to minimie the distortions.

[jase (Jason)]

Roger, productive imaging you've displayed. My pick of the bunch is the wide field Orion image. Looks sharp and captures such a vast area. You know when you're getting the framing right when you've got Barnards loop as well as the witchhead nebula. The LMC is equally impressive. Very nicely done and good to see more of your work.

[rogerg (Roger)]

Originally Posted by jase

Roger, productive imaging you've displayed. My pick of the bunch is the wide field Orion image. Looks sharp and captures such a vast area. You know when you're getting the framing right when you've got Barnards loop as well as the witchhead nebula. The LMC is equally impressive. Very nicely done and good to see more of your work.

Your review and encouragement is much appreciated Jase, thanks.

It's a shame that while the witchhead is in it, it's significntly distorted due to the lens. Check out the shape of these stars from a 100% crop Not quite the seaguls of F/1.4 but not circular either.

I think I will do some longer exposres with the witchhead more central next time, as it comes out surprisingly well on the un-modded dslr.

[multiweb (Marc)]

Originally Posted by rogerg

Thanks

I just stop it down in focal ratio, so from F/1.4 to F/2.8 on the camera settings. I don't stop down the actual apperture of the lens, I think that would only make the situation worse but haven't tested it to have proof Stopping the focal ratio to F/2.8 has a dramatic effect on the picture quality, the corners go from swan shaped stars to circular stars, and F/2.8 is still quite fast

Zooming in/out will change the distortions evident from your lens but I think it's a case of trial and error. I've tried different zooms with my 17-40 and 70-200 and find it's not necessarily the long end (40mm and 200mm) that has less distortions, but there's always a best place, if keen to minimie the distortions.

Thanks for the info Roger. I'll try it out next time.

[Hagar (Doug)]

Lovely collection of images Roger, my vote goes to LMC.

Well done.

[rogerg (Roger)]

Originally Posted by Hagar

Lovely collection of images Roger, my vote goes to LMC.

Well done.

Originally Posted by seeker372011

great results,

Thank you both

[prokyon (Werner Probst)]

Very nice results! My favorite ist the LMC. I have the same lens, I shoult use it more often.

Cheers

Werner

[luigi]

Fantastic images Roger, I like Orion a lot, you got a lot of light and the AT tracking was spotless!
I think you can combine that with shorter exposures of M42 and it'll be awesome!

[guyroch]

If this is the result you get when you're simply having fun I can't wait to see what you can produce when you really get down to business! Good job!

Guylain