#1  
Old 20-07-2011, 10:45 AM
niko's Avatar
niko
Registered User

niko is offline
 
Join Date: Feb 2007
Location: Melbourne, Victoria
Posts: 1,053
Canon widefield lens advice

Hi everyone,

I've been enjoying taking star trails and widefields for some time with my Canon 350D. I've got an 18-55mm lens but I really struggle to get accurate focus and find my eyesight no longer good enough to confirm the focus on the back screen. I seem to have wasted many nights taking a series of shots that are too fuzzy to use. This seems partly because the focus ring on the lens goes part infinity.

So - looking for a fixed focal length (or short focal length) lens that focuses on infinity without having to step it back.

Can anyone suggest a suitable lens. I've heard good things about the Tokina 11-16. Does it focus easily?

Are there other recommendations?

many thanks

niko
Reply With Quote
  #2  
Old 20-07-2011, 10:54 AM
Poita (Peter)
Registered User

Poita is offline
 
Join Date: Jun 2011
Location: NSW Country
Posts: 3,585
Use the zoom feature on the screen on the back of your camera to get the focus right and take a few pictures and keep adjusting the focus.
Reply With Quote
  #3  
Old 20-07-2011, 12:06 PM
multiweb's Avatar
multiweb (Marc)
ze frogginator

multiweb is offline
 
Join Date: Oct 2007
Location: Hinchinbrook
Posts: 18,138
Quote:
Originally Posted by niko View Post
Hi everyone,

I've been enjoying taking star trails and widefields for some time with my Canon 350D. I've got an 18-55mm lens but I really struggle to get accurate focus and find my eyesight no longer good enough to confirm the focus on the back screen. I seem to have wasted many nights taking a series of shots that are too fuzzy to use. This seems partly because the focus ring on the lens goes part infinity.

So - looking for a fixed focal length (or short focal length) lens that focuses on infinity without having to step it back.

Can anyone suggest a suitable lens. I've heard good things about the Tokina 11-16. Does it focus easily?

Are there other recommendations?

many thanks

niko
Lenses are a bit of a hit and miss. Sometime you get a good one. I focus with a mini-bathinov mask and keep the lens at full aperture so I don't get diffraction spikes in the way. Then I f-stop it. Some lenses are very easy to focus. Some have a very tight CFZ.
Reply With Quote
  #4  
Old 20-07-2011, 12:26 PM
Omaroo's Avatar
Omaroo (Chris Malikoff)
Let there be night...

Omaroo is offline
 
Join Date: Aug 2006
Location: Sydney/Cooma
Posts: 7,628
Quote:
Originally Posted by niko View Post
Hi everyone,

So - looking for a fixed focal length (or short focal length) lens that focuses on infinity without having to step it back.
Not sure you'll find one Niko. I've heard from many that the reason they go beyond infinity at the final stop is to allow for expansion/contraction.

I've been using the mini-Bahtinovs for ages on my camera lenses, and with live view on the 5D-II it works very well as you can dial in focus on a bright star in seconds as you watch. The 350D, without it, will still work, but you need to expose for at least 10 secs at ISO800 on a fairly bright star to see the diffraction pattern well - which you need to center in frame as best you can so that zooming in to inspect the result doesn't require you to jog the object into view all the time.
Reply With Quote
  #5  
Old 20-07-2011, 03:33 PM
niko's Avatar
niko
Registered User

niko is offline
 
Join Date: Feb 2007
Location: Melbourne, Victoria
Posts: 1,053
Thanks everyone.

Chris/Mark - I tried the bahtinov mask without much luck at 18mm I just didn't get the spikes - I'll try again centred on a brighter star. I just find even zooming in on the camera's screen doesn't help much. Guess I will have to run it through the laptop so I can see a bigger piccie.

I went to look at the Tonkina 11-16 and the Sigma 10-22 - holy moly, wasn't expecting them to be so much. Guess you get what you pay for.

niko
Reply With Quote
  #6  
Old 20-07-2011, 05:37 PM
multiweb's Avatar
multiweb (Marc)
ze frogginator

multiweb is offline
 
Join Date: Oct 2007
Location: Hinchinbrook
Posts: 18,138
Quote:
Originally Posted by niko View Post
Thanks everyone.

Chris/Mark - I tried the bahtinov mask without much luck at 18mm I just didn't get the spikes - I'll try again centred on a brighter star. I just find even zooming in on the camera's screen doesn't help much. Guess I will have to run it through the laptop so I can see a bigger piccie.

I went to look at the Tonkina 11-16 and the Sigma 10-22 - holy moly, wasn't expecting them to be so much. Guess you get what you pay for.

niko
How thin are the slits? You need really thin ones. You get some good lenses on eBay. My Pentax 200mm costed $60.00 shipped. Best is to check pics and see what lens they were taken with,f-stop, etc... so you have an idea of what works and what doesn't. Don't go spend a lot then figure out later it doesn't do the job.
Reply With Quote
  #7  
Old 20-07-2011, 08:54 PM
koputai's Avatar
koputai (Jason)
Registered User

koputai is offline
 
Join Date: Nov 2007
Location: Canberra, Australia
Posts: 1,633
My copy of the Canon EF35mm f/2.0 focuses at infinity at the stop, and provides a good sized field.

Cheers,
Jason.
Reply With Quote
  #8  
Old 20-07-2011, 09:26 PM
PeterO's Avatar
PeterO
Registered User

PeterO is offline
 
Join Date: Jul 2005
Location: Traralgon Vic
Posts: 129
I use the Tokina 11-16, great lens for real wide field however focus on stars is some where about the infinity symbol meaning you still need a mask or live view. Lately I have just been connecting up the Acer Iconia tablet and using the nice large 10" screen when adjusting the focus.

Cheers, Peter
Reply With Quote
  #9  
Old 20-07-2011, 09:35 PM
mithrandir's Avatar
mithrandir (Andrew)
Registered User

mithrandir is offline
 
Join Date: Jan 2009
Location: Glenhaven
Posts: 4,161
Quote:
Originally Posted by niko View Post
I went to look at the Tonkina 11-16 and the Sigma 10-22 - holy moly, wasn't expecting them to be so much. Guess you get what you pay for.
I have one complaint about my Tokina 11-16. The FOV is so huge I can't use it at home because either the house or trees get in frame and they are illuminated by street lights. Up at Glenhaven I get some part of the Sydney skyglow no matter what direction I point it.

Image included just to give you some idea of what it covers. Unprocessed apart from resize to 25%. The eastern horizon is just out of frame at the bottom. Sydney is towards bottom right. Scorpio occupies about 20% of the frame.

File Modification Date/Time : 2011:06:24 20:47:24+10:00
Exposure Time : 25 sec
F Number : 2.8
Exposure Program : Manual
ISO : 800
Focal Length : 11.0 mm
White Balance : Daylight
Attached Thumbnails
Click for full-size image (DSC03661-25pct.JPG)
184.2 KB56 views
Reply With Quote
  #10  
Old 21-07-2011, 07:11 AM
multiweb's Avatar
multiweb (Marc)
ze frogginator

multiweb is offline
 
Join Date: Oct 2007
Location: Hinchinbrook
Posts: 18,138
Quote:
Originally Posted by mithrandir View Post
I have one complaint about my Tokina 11-16. The FOV is so huge I can't use it at home because either the house or trees get in frame and they are illuminated by street lights.
Same problem at home. I usually have to sigma reject my house gutter the first few subs looking east.
Reply With Quote
  #11  
Old 21-07-2011, 08:16 AM
hotspur's Avatar
hotspur (Chris)
Registered User

hotspur is offline
 
Join Date: Apr 2009
Location: south east QLD,Australia
Posts: 2,851
Quote:
Originally Posted by PeterO View Post
I use the Tokina 11-16, great lens for real wide field however focus on stars is some where about the infinity symbol meaning you still need a mask or live view. Lately I have just been connecting up the Acer Iconia tablet and using the nice large 10" screen when adjusting the focus.

Cheers, Peter
That is a handy suggestion!,to the OP I have the 10-22 mm Canon EF-S wide field lens-I am amazed the sharpness of it,and could very much recommend it.I have heard very good things about the Tonika 11-16 mm,and I think it would be a lot cheaper than the Canon one.

Here is a 15 minute exp with my canon copy.
Attached Thumbnails
Click for full-size image (IMGannette_5583.jpg)
203.4 KB56 views
Reply With Quote
  #12  
Old 21-07-2011, 08:31 AM
niko's Avatar
niko
Registered User

niko is offline
 
Join Date: Feb 2007
Location: Melbourne, Victoria
Posts: 1,053
many thanks again guys

I think maybe the slits on the bahtinov are too wide
Reply With Quote
  #13  
Old 27-07-2011, 08:01 AM
En1gma's Avatar
En1gma (Robert)
Registered User

En1gma is offline
 
Join Date: Sep 2009
Location: Sydney, Australia
Posts: 336
Just to add on the focusing side of things, what I had done as I didn't have a bhatinov mask. Is focus the lens in daylight (eg building/tree etc) to infinity then lock it in place with a couple of pieces of masking tape. That way I just needed to setup and shoot. Depending on the weather and atmos conditions, sometimes I would get a minimal amount of subs out of focus.

Moving forward for lens, I too am deciding on getting the tokina as I have heard veryngood things about them, so I'm sure you cannot go wrong.

Rob
Reply With Quote
  #14  
Old 27-07-2011, 07:39 PM
batema's Avatar
batema (Mark)
Registered User

batema is offline
 
Join Date: Jul 2006
Location: Sunshine Coast
Posts: 1,807
Hello Niko,

Ever since I have been in this hobby a friend put me onto this program called Focusassist and I think that this is the website. http://jstanley.pingerthinger.com/focusassist/

I also downloaded a magnifyer program that allows me to zoom in. The focus assist allows you to take an image at different ISO and times and then downloads the image to the screen of the program. So you can see the stars and then I move my magnifyer program over a selected star ( i have the zoom set to about 8x and look at the focus of the star. If it looks fuzzy I adjust the focus, keep the magnifyer there and shoot again and the new image downloads and I can see if the adjustment was OK and then I keep going until the star will basically resolved to like a single pixel or close enough. I have done this for ever and it is very easy but have not used a batinov mask at all so can not compare.

Mark
Reply With Quote
  #15  
Old 27-07-2011, 08:22 PM
Octane's Avatar
Octane (Humayun)
IIS Member #671

Octane is offline
 
Join Date: Dec 2005
Location: Canberra
Posts: 11,158
Canon EOS Utility Remote Shooting enabled; tick the 200% zoom box. Pop on your Bahtinov mask and load the free Bahtinov Geabber software, and you're set.

H
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 12:14 PM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Advertisement
OzScopes Authorised Dealer
Advertisement
Lunatico Astronomical
Advertisement
Celestron Australia
Advertisement
SkyWatcher Australia
Advertisement
Bintel
Advertisement
Meade Australia
Advertisement
NexDome Observatories
Advertisement
Astronomy and Electronics Centre
Advertisement