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Archive 2007 · Test: Sun stars of 20 mm lenses

Stefan Rohloff
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p.1 #1 · p.1 #1 · Test: Sun stars of 20 mm lenses

I have just completed my 20 mm test.

It's a bit special:
I wanted to learn about the shape of the star you get, when you point a 20 mm lens directly into the sun - digital and analog.

I don't know if someone else cares about the shape of sun stars ... but the tests are online now:

http://www.stefanrohloff.de/20_sunstar.php

One analog example out of the test: f/16, 1/160 (EOS 3)


	http://www.stefanrohloff.de/datatests/stan_ol21.jpg

One digital example out of the test: f/16, 1/125 & 1/250 (EOS 20D)


	http://www.stefanrohloff.de/datatests/stdi_ol21.jpg

Unfortunately slides seem to handel direct sun light much better than digital chips.
Are your experiences the same?

Analog I likes stars with only few rays (6) most.
Digital I probably prefer the stars with many rays (18).
What do you think about the number of rays? I'm very interested in your opinions

Stefan

The tests: http://www.stefanrohloff.de/lenstests.php

Edited by Stefan Rohloff on Dec 30, 2007 at 09:28 PM GMT

Dec 09, 2007 at 02:00 PM

Mike Tuomey
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p.1 #2 · p.1 #2 · Test: Sun stars of 20 mm lenses

stefan, thanks very much for posting your testing. i like especially that you didn't force conclusions on the reader!

as to number of rays, i've always preferred fewer yet well-defined rays, but i agree that the digi files seem to look better with more rays. interesting.

Dec 11, 2007 at 11:51 AM

StevenPA
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p.1 #3 · p.1 #3 · Test: Sun stars of 20 mm lenses

Very interesting test, Stefan! Please continue your testing with other focal lengths, not just wide angles.

I do a lot of night photography and am always interested in how point sources of light are rendered by different lenses. The Contax C/Y lenses are easily my favourites, followed by the Olympus OM lenses. I haven't seen many Leica sun stars, but they're probably pretty nice as well. My least favourite is probably the 17-40L (ball of mush at any aperture) and Contax N24-85 (slightly less mushy ball of mush). I've always preferred fewer rays, whether on film or digital.

16-35II, f/8
http://www.pbase.com/stevenpa/image/82564943/original.jpg
Contax 35-70, f/8 or 11
http://www.pbase.com/stevenpa/image/82564949/original.jpg

It's interesting to see the OM 21/3.5's "red ring" of flare in your sample because that's exactly what my copy does as well. I guess it's a characteristic of this lens.

http://www.pbase.com/stevenpa/image/84212672/original.jpg

Dec 11, 2007 at 06:09 PM

cogitech
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p.1 #4 · p.1 #4 · Test: Sun stars of 20 mm lenses

Wonderful! Bravo!

Dec 11, 2007 at 06:28 PM

cogitech
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p.1 #5 · p.1 #5 · Test: Sun stars of 20 mm lenses

StevenPA wrote:
Very interesting test, Stefan! Please continue your testing with other focal lengths, not just wide angles.

I do a lot of night photography and am always interested in how point sources of light are rendered by different lenses. The Contax C/Y lenses are easily my favourites, followed by the Olympus OM lenses. I haven't seen many Leica sun stars, but they're probably pretty nice as well. My least favourite is probably the 17-40L (ball of mush at any aperture) and Contax N24-85 (slightly less mushy ball of mush). I've always preferred fewer rays, whether on film or digital.

16-35II, f/8
http://www.pbase.com/stevenpa/image/82564943/original.jpg
Contax 35-70, f/8...Show more →

Despite the "red ring", it looks to me like the Oly produces the best colour and contrast in these night shots (but the worst stars).

Dec 11, 2007 at 06:41 PM

rico
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p.1 #6 · p.1 #6 · Test: Sun stars of 20 mm lenses

Ray geometry is a function of aperture shape, so Leica should have no clear advantage. Here is the Elmar 90 (M mount) at f/5.6

Dec 12, 2007 at 09:27 PM

StevenPA
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p.1 #7 · p.1 #7 · Test: Sun stars of 20 mm lenses

rico wrote:
Ray geometry is a function of aperture shape, so Leica should have no clear advantage.

I should qualify my statement above about Leica lenses producing nice star effects. I didn't mean to imply that they had a special advantage in this regard; rather the R lenses that I've tried, with the exception of the 35-70/4, have all been older lenses that don't have the more modern roundish aperture blades. It's my understanding that the more square or strait the aperture blades are, the more pronounced the star effect will be. Is that correct?

Is there a way to tell how pronounced the star effect will be or how many rays it will have just by looking through the lens itself?

Dec 13, 2007 at 07:00 PM

Stefan Rohloff
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p.1 #8 · p.1 #8 · Test: Sun stars of 20 mm lenses

Mike, interesting that you have the same feeling about the numer of rays ...

Steven, thanks for your images. I like the star of the 16-35 II most. The 16-35 II is supposted to have less problems with ghosting / reflexions than the 16-35 I. Can you confirm this? Have you compared ghosting of 16-35 II and Zuiko 21? In my test of ghosting / relexions the Zuiko has very little ghosting apart from the red ring. So if the 16-35 II would be comparable to the Zuiko in this concern it would be a very good result for the 16-35 II.

Yes, you can tell, how many rays there will be:
4 blades ---> 4 rays (Leica Super-Angulon 4/21)
5 blades ---> 10 rays (Pentax)
6 blades ---> 6 rays
7 blades ---> 14 rays
8 blades ---> 8 rays
9 blades ---> 18 rays (Sigma 20, Zeiss ZF)

To see how pronounced the effect will be you probably you have to test the lens.

I haven't seen the star of the Leica Super-Angulon 4/21 yet. Would be interesting how nice a 4 ray star looks like.

Rico, thank you for your image of the Leica star.

Stefan

Edited by Stefan Rohloff on Dec 30, 2007 at 09:29 PM GMT

Dec 14, 2007 at 03:07 AM

rico
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p.1 #9 · p.1 #9 · Test: Sun stars of 20 mm lenses

Ah, even/odd rule. With ten rays, the Elmar 90 and its ten blades is behaving normally. I should star-test my other Elmar, a 50/2.8 classic: it has 15 blades!

Dec 14, 2007 at 04:30 AM

StevenPA
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p.1 #10 · p.1 #10 · Test: Sun stars of 20 mm lenses

Stefan,

Thanks for the info. The 16-35II belongs to a friend, so I've not really had the chance to inspect its flare resistance. I'm not too impressed with the flare resistance of the OM 21/3.5. There are times when it will pick up flare in the oddest of situations. Here's an example - the sun is behind me. Don't ask me what that other photographer is doing in my shot; he jumped in, wrecking it, and I wasn't pleased!

http://www.pbase.com/stevenpa/image/89679861/original.jpg

Dec 14, 2007 at 05:03 AM

crazeazn
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p.1 #11 · p.1 #11 · Test: Sun stars of 20 mm lenses

should have kicked him in the gochu

Dec 14, 2007 at 09:00 AM

StevenPA
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p.1 #12 · p.1 #12 · Test: Sun stars of 20 mm lenses

crazeazn wrote:
should have kicked him in the gochu

now now...

Dec 14, 2007 at 09:07 AM

cogitech
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p.1 #13 · p.1 #13 · Test: Sun stars of 20 mm lenses

I'd be willing to bet the sun is reflecting off of one of those buildings in the left background. From the shadows, I can see the angle of light and it is not difficult to imagine the sunlight coming in from that angle, striking the windows on a building, and nailing part of your front element. The shape and positioning of the flare supports the theory. Whatever windows were reflecting the sunlight are out of the frame somewhere.

Still, other lenses may certainly have handled that better. Is your 21/3.5 an MC version?

Dec 14, 2007 at 09:48 AM

StevenPA
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p.1 #14 · p.1 #14 · Test: Sun stars of 20 mm lenses

A plausible explanation, Paul. And yes, the lens is MC with a serial number of 117xxx. The coating looks reddish on the outer element and greenish on an internal element. This is probably what induces the bright red ring of flare.

Dec 14, 2007 at 10:07 AM

cogitech
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p.1 #15 · p.1 #15 · Test: Sun stars of 20 mm lenses

Hmmm. Mine's SC. I aught to check if it has the "red ring" some time...

Dec 14, 2007 at 11:07 AM

Stefan Rohloff
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p.1 #16 · p.1 #16 · Test: Sun stars of 20 mm lenses

Rico, wow, 15 blades would mean 30 rays !!

Steven, that is really strange ghosting ... I think, Paul should be right.

I think, both SC and MC have the red ring. Look at this: One is SC, the other is MC.
There is the same pattern of ghosting ... just some parts of the ghosting are "multicoated away"

... colors of ghosting have shifted and there is different over all flare ... may be the SC-ring is orange, not red !?

http://www.stefanrohloff.de/temp/Oly21_SC_MC.jpg

Stefan

Dec 14, 2007 at 12:09 PM

cogitech
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p.1 #17 · p.1 #17 · Test: Sun stars of 20 mm lenses

A wonderful comparison. Thanks!

Dec 14, 2007 at 05:36 PM

godzakka
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p.1 #18 · p.1 #18 · Test: Sun stars of 20 mm lenses

Thanks so much to everyone for contributing to this. I love getting the star effects when taking night shots, and have only recently become aware of the relationship to the number of blades/star shape.

I noticed above that StevenPA's 16-35 shots star points appear to be "sharper" as they extend away from the light source, whereas the Contax's star points appear to diverge as they extend away from the light source. Is this somehow a function of the number of blades or type of blades? My 10-22 often diverges (as the Contax does, but even moreso) but obviously with only 6 star points.

Dec 25, 2007 at 08:17 PM


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