Do all Wide angle lenses distort stars that are off center frame?

[erotavlas]

Hi I just bought a new wide angle lens for my camera and I've been testing it out. I tried a shot in the city to capture a few stars and noticed the stars near the edges and corners have a weird shape. I'm guessing this is coma? Or something else. I had the lens wide open at f2.8. I'll try some more tests at other apertures, but I bought it primarily to get that f2.8.

http://sdrv.ms/17BcDsq

[tedrampart]

this is pretty normal for any lens really when shooting wide open, it's just really apparent on some wider angle lenses.. I usually stop down a couple stops to help with that, so on a 2.8 I'd shoot f4, maybe f3.5 if I want the extra bit of light captured.

mind you some lenses will have this more than others, it's from barrel distortion and coma. There are some lenses that handle that better than others, but the wider the lens, the harder it is to control. sometimes you can use tools in ACR to help correct it.

[erotavlas]

I just feel like I spent the extra money to get f2.8 when I could have saved it and got another lens that starts at f4. If you have to stop down any way to reduce this then what is the point of buying faster lens for astronomy use?

[tedrampart]

if you got an f4 lens, you'd have to stop down a couple stops with it as well.. I mean, you don't have to stop down, if you don't notice it unless you pixel peep, having the 2.8 speeds will still be usable.. stopping down just helps sharpen things up and remove some vignette. stopping down will also help you hyperfocus..

I've seen wide angle lenses at f4-5.6 that are pretty much garbage til f11.. we're talking borders out of focus level bad.. so having the 2.8 will have better optics.

my 50mm 1.8 lens has artifacts like that unless I shoot at f4.. but I also prefer f4 because I get nicer star spikes, and a flatter field, meaning sharper stars in the edges/corners.

EDIT - I should point out, that having a faster lens doesn't mean that image quality wide open will be guaranteed better.. it does mean however, that stopping down to the level of the cheaper lenses wide open you will be guaranteed better image (eg an f/2.8 stopping down to f/4 will be a better image than the f/4 at f/4).. so you're still getting a faster usable f-stop value.. I don't know any lens of any company that is perfectly flat and sharp wide open.. even zeiss suffer wide open.. plus stopping down gives star points, wide open usually gives me bloated stars..

[Ruud]

Check out the Samyang 14mm F/2.8 in this thread: A Touching Moment!! (=^0^=)

It is reviewed here: Samyang 14mm f/2.8 IF ED UMC Aspherical - Full Format Review / Test Report

[camknox]

What camera and lens are you using? A lot rides on the build quality and even then you could get one from a bad run.

I use the Tokina 11-16 AT-X II f/2.8 for my ultra wide on the crop sensor. At wide open it has no noticeable vignetting or coma. Stopping it down to f/3.2 is a fair trade off though.

[tedrampart]

Check out the Samyang 14mm F/2.8 in this thread: A Touching Moment!! (=^0^=)

It is reviewed here: Samyang 14mm f/2.8 IF ED UMC Aspherical - Full Format Review / Test Report

I have one of these, and one of their 24mm's.. both are excellent performers even wide open. I just heard they have a 16mm coming out as well. good cheap manual lenses.

[erotavlas]

What camera and lens are you using? A lot rides on the build quality and even then you could get one from a bad run.

I use the Tokina 11-16 AT-X II f/2.8 for my ultra wide on the crop sensor. At wide open it has no noticeable vignetting or coma. Stopping it down to f/3.2 is a fair trade off though.

Well the lens I tested is a Zeiss Touit 12mm f2.8 for Sony E-mount (on a Sony Nex 5N). Hopefully tomorrow I'll get a chance to drive away from city lights and take some better images. I would think the Zeiss lenses have better build quality, and quality control. How likely would it be I got a bad one, or maybe they weren't designed with coma in mind (like some high end Canon lenses)

I found this link that shows how some expensive Canon lenses have really bad coma even though they are sharp lenses and high quality. They also mentions the Samyang as a good alternative with low coma.

Into The Night Photography: Overcoming Coma Aberration - Part 2

[erotavlas]

I also found this site.

Blog @ BorrowLenses

It says to look for lenses with aspheric element. According to the specs of my lens it has two elements with aspheric surface.

Touit 2.8/12 | ZEISS International

[camknox]

Well the lens I tested is a Zeiss Touit 12mm f2.8 for Sony E-mount (on a Sony Nex 5N). Hopefully tomorrow I'll get a chance to drive away from city lights and take some better images. I would think the Zeiss lenses have better build quality, and quality control. How likely would it be I got a bad one, or maybe they weren't designed with coma in mind (like some high end Canon lenses)

I found this link that shows how some expensive Canon lenses have really bad coma even though they are sharp lenses and high quality. They also mentions the Samyang as a good alternative with low coma.

Into The Night Photography: Overcoming Coma Aberration - Part 2

I'm not familiar with the Sony range, or for that matter the Zeiss Touit lenses. I had a read through the literature but I couldn't find if the lens was made for a crop sensor or full frame. Sometimes using a full frame lens on a crop sensor can yield unwanted aberrations.