Free Shipping on ALL Products
camera reviewsbest cameraslens reviewsphotography tipscamera forumvideo toursphotography bookssupport me
It is currently Sat Jul 26, 2014 5:54 pm

All times are UTC




Post new topic Reply to topic  [ 146 posts ]  Go to page Previous  1, 2, 3, 4, 5, 6, 7, 8 ... 10  Next
Author Message
 Post subject:
PostPosted: Tue Nov 13, 2007 8:54 am 
Thanks for the link Bob. It was quite interesting, I had no idea that people were campaigning about this kind of stuff. Does your Hutech filter reflected artificial light as well? I think that's my main problem now.


Top
  
 
 Post subject:
PostPosted: Tue Nov 13, 2007 9:25 am 
Offline
Moderator
User avatar

Joined: Sat Sep 30, 2006 4:30 pm
Posts: 9805
Location: UK
Graham,

The filter is a narrow band affair and specifically cuts out the main sodium emission line. Anything else gets through.

Bob.

_________________
Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


Top
 Profile  
 
 Post subject:
PostPosted: Tue Nov 13, 2007 9:36 am 
Hi Bob,

Thanks for the quick reply. I suppose this means it won't work for me then. Argh...stupid lights. :evil:


Top
  
 
 Post subject:
PostPosted: Tue Nov 13, 2007 12:34 pm 
Another great Photo Bob
Thanks for sharing ! :D
200mm seems very usable ..


Top
  
 
 Post subject:
PostPosted: Tue Nov 13, 2007 12:43 pm 
Offline
Moderator
User avatar

Joined: Sat Sep 30, 2006 4:30 pm
Posts: 9805
Location: UK
DavidL wrote:
200mm seems very usable ..

Absolutely. No tendency to creep under its own weight, either. It is heavy enough to warrant the use of my optional tripod ring, however, as using the 40D's tripod mounting point means the whole assembly tends to rotate under the unusual attitudes, even when screwed in quite tightly.

Bob.

_________________
Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


Top
 Profile  
 
 Post subject:
PostPosted: Wed Dec 12, 2007 11:09 pm 
Offline
Moderator
User avatar

Joined: Sat Sep 30, 2006 4:30 pm
Posts: 9805
Location: UK
Hi folks,

I was reading this review of the Canon EOS 1Ds Mark III this afternoon :mrgreen: and one of the test shots was a 30 minute exposure at f/16 and ISO 100 to capture some star trails.

That prompted me to wonder how my lowly EOS 40D would compare as I have never tried such a long exposure before. I used my EF 24-105mm f/4L IS USM lens at 24mm and also used my Hutech filter to cut out as much of the glare from the local sodium street lights as I could. A standard Bogen tripod was used to hold the camera. The lens was focused at infinity with the aid of the 40D's remote Live View capabilities earlier in the evening. For the exposure itself the notebook computer was disconnected and the 1966 second exposure (roughly 30 minutes) was controlled with an RS-80N3 Remote Switch. During the exposure I kept nice and warm watching a recording of this week's Monday Night Football game (Saints at the Falcons). 8) In order to try and make a fair comparison I shot at f/16 and ISO 100.

Here is the processed and resized uncropped JPEG:
    Image
The image is clickable to allow you to download the original unprocessed JPEG as it came out of the camera.

As you can see, the local village street lights still made their presence felt in the lower right of the image. If you download the original JPEG you can see a few hot pixels. Unsympathetic processing can reveal quite a few hot pixels but integrated over 30 minutes or so I guess it's fair to say that even a slightly warm pixel will get saturated so I'm happy enough.

Finally, here's a 100% crop. The only post-processing done is to alter brightness and contrast to approximate the background of the image (not the star trail) very roughly to that of the image shown in the 1Ds Mark III review to try and get some idea of sensor noise. Here it is:
    Image
No extra noise processing was done and I deliberately selected an area which included a hot pixel. Don't get me wrong - I would love a 21.1MP 1Ds Mark III if money were no object and its IQ is really in a different league - but I think the 40D has performed pretty well considering it is less than one fifth the price of its big brother.

For those of you still reading :!: and who want to try your hand at star trails I think that ISO 100 and f/16 are much too conservative if you can find a dark site where the local authority isn't so vain that it wants to try and light the Universe which is, after all, very big. It's also a good idea to avoid trying this if the Moon is visible. The issue here is that the number of stars you capture is, for a given focal length, fixed by the combination of ISO and f-number whilst the length of the trails is solely limited by how long your chosen combination of ISO and f-number takes to capture the stray light in the sky.

If you decide to give it a go then, as I write, now is a good time as the Moon is still nearly new. Good luck.

Bob.

_________________
Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


Top
 Profile  
 
 Post subject:
PostPosted: Thu Dec 13, 2007 12:04 am 
Offline
Site Admin
User avatar

Joined: Tue Nov 08, 2005 3:32 pm
Posts: 9962
Location: Queenstown, New Zealand
Hi Bob, nice shot! You must have also seen the famous exposure taken at the Anglo Australian Telescope which lasted something like 6 hours for massive star trails - plus some wavy torch action to illuminate the dome... Go on, try for a couple of hours! What's the maximum exposure the 40D can do on one charge...?

PS - in an off-topic sidenote, I once met David Malin, the famous astro-photographer from the AAT and he said the first few attempts of that long exposure shot were runined by colleagues 'writing' rude words in the air with their torches!


Top
 Profile  
 
 Post subject:
PostPosted: Thu Dec 13, 2007 12:17 am 
Offline
Moderator
User avatar

Joined: Sat Sep 30, 2006 4:30 pm
Posts: 9805
Location: UK
Thanks Gordon.

I don't know if it's still in print but I have a copy of David Malin's "A View of the Universe". Recommended reading if you can find a copy. Quite amazing what he did with film and I wouldn't be surprised if his techniques were the inspiration for a lot of the digital processing that has now become almost routine.

I think I will pass on any further torture tests of my 40D's sensor if you don't mind. Bearing in mind the warnings that continued use of Live View on hot days can be an issue I think that even on cold winter nights discretion is the better part of valour. :idea:

Bob.

_________________
Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


Top
 Profile  
 
PostPosted: Thu Dec 27, 2007 9:33 pm 
Offline
Moderator
User avatar

Joined: Sat Sep 30, 2006 4:30 pm
Posts: 9805
Location: UK
Hi folks,

A couple of weeks ago, during the new Moon, we were blessed with a really clear and frosty night so the telescope, camera, comfy chair and notebook computer were bundled into the back of the car and I drove to a spot several miles away from any street lights. With any large centres of population (Witney, Oxford, Cirencester Cheltenham etc.) well over the horizon I had real hopes of going deep so I left the Hutech sodium street light filter behind. Otherwise the set-up was as described before but, for new readers, here is a quick reprise.

My EOS 40D was piggybacked on top of the telescope. The telescope optics weren't used but this arrangement allows me to take advantage of the motorised mounting's ability to track the stars, so allowing longer time exposures without the star trails. The notebook computer was used to take advantage of the 40D's remote Live View functionality and the EOS utility software's "intervalometer" was used to run the exposure sequences. I used my 85mm f/1.2 lens wide open at f/1.2 and the camera was set to ISO 400 and a sequence of twelve separate four minute exposures were made of the constellation of Orion. Each exposure was followed by a three minute rest to allow the camera's sensor to cool down and air temperature started just above freezing and fell to several degrees below during the session, as my feet kept reminding me. :evil: Of the twelve exposures six were taken of the top half of Orion and six of the bottom half.

It had been my intention to take another six exposures in precisely the same way but with the lens cap on. However, the cold proved too much for my notebook's battery and it died leaving me with just the one "dark frame".

    Processing
Processing is critical to success for this type of shot. To illustrate this here are two thumbnails from the original twelve, unprocessed apart from resizing, with the top half of Orion on the left.
    Image..Image
Not too promising at first glance and I confess that thought was partly responsible for the delay in processing the images, though I will also blame Christmas! That orange glow is the result of street lights many miles away and not sensor noise. So the profligacy with which the local authorities waste electricity by trying to light up the Universe means I still have to consider using my Hutech filter, despite the fact that it introduces diffraction spikes into the image around bright stars.

Because I wanted to mosaic the top and bottom halves of Orion together I decided to start processing by opening each of the RAW files in Canon's DPP and correcting for lens distortion and vignetting before saving once more in RAW. I also did this with all of the ancillary files needed to complete processing using ash's "Diamonds from the Rough" primer for Christian Buil's excellent IRIS software. My first deviation from this methodology was to align the "lights" using manually selected stars. It takes more time but the results are more predictable.

With two images (top and bottom of Orion) produced from each stack of six it was time to do some serious image post-processing and here I stepped away from ash's primer. Although DPP had done an initial correction for vignetting the subsequent processing needed to bring out faint details means that more needs to be done. I followed the BIN_DOWN method described here using two passes. This was done for each of the two images. I then used the Modified Equalisation function to enhance the faint nebulosity. The two images were then exported from IRIS as TIFF files so they could be opened in Photoshop CS2.

The first task in Photoshop was to use the Levels function to get the background sky as dark as possible without losing any significant nebulosity. I then fired up its Photomerge dialog and pointed it at the two files. The result was a very pleasant surprise as not only did Photoshop do all the required geometry calculations but it also equalised the backgrounds. There are a few artefacts if you look very carefully but only the dedicated pixel peepers will be aware of them. With the mosaicked image assembled the final step was some intensive cosmetic tweaking to the colour and a mixture of sharpening and blurring. Here is the final result (apologies for exceeding the normal recommended image height but at least I kept the width down!):
    Image
    Clickable if you want to view the full size JPEG (4MB)
Many of you will be familiar with Orion but with so many stars visible it isn't so easy to navigate so here is a handy image I've plucked from the Web:
    Image
Though the resolution in this map is necessarily poorer and not so many stars are visible it is possibly worth pointing out that there is slightly more of the red nebulosity visible. This highlights a problem with using unmodified DSLRs for astrophotography as the filter just in front of the sensor substantially reduces its sensitivity to the Hydrogen Alpha red emission line which is often a major feature in nebulae.

Bob.

_________________
Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


Top
 Profile  
 
 Post subject:
PostPosted: Thu Dec 27, 2007 9:55 pm 
Offline
Moderator
User avatar

Joined: Sun Nov 05, 2006 11:08 pm
Posts: 7923
Location: Germany
Let me just say: WOW!
And that 85mm F/1.2 is some serious glass :wink:

_________________
Thomas (beware: Nikon-fanboy and moderator!) My Lens Reviews, My Pictures, My Photography Blog
D800+assorted lenses


Top
 Profile  
 
 Post subject: .
PostPosted: Thu Dec 27, 2007 10:27 pm 
Incredible shot, and amazing processing, and once again Bob you sold me on that lens!! Now I’m seeing myself more broke than ever :shock:


Top
  
 
 Post subject:
PostPosted: Fri Dec 28, 2007 2:49 am 
Offline
Site Admin
User avatar

Joined: Tue Nov 08, 2005 3:32 pm
Posts: 9962
Location: Queenstown, New Zealand
Hi Bob, very nice post!

And congrats on capturing the elusive horsehead nebula! I demand a 100% crop from that portion please!

PS - that's still amazing the amount of light pollution on those shots though - you really need to get yourself somewhere really dark sometime! How about that trip to Arizona?!


Top
 Profile  
 
 Post subject:
PostPosted: Fri Dec 28, 2007 1:15 pm 
Offline
Moderator
User avatar

Joined: Sat Sep 30, 2006 4:30 pm
Posts: 9805
Location: UK
Gordon Laing wrote:
... congrats on capturing the elusive horsehead nebula! I demand a 100% crop from that portion please!
.
you really need to get yourself somewhere really dark sometime! How about that trip to Arizona?!...

It's not pretty but you asked for it! I took a crop from the same portion of the two stacked images which I had combined previously to form the mosaic. I then used IRIS to stack these so I now had effectively a stack from twelve images. Because only a small portion of the original frames was used I was able to do just a single pass to remove any sky gradient and then used IRIS' Modified Equalisation function as before. Again the image was exported to Photoshop for cosmetic tweaks. Here is the resulting 100% crop:
    Image
As I said, it's not pretty but it's just about recognisable. Even worse, I almost prefer the 100% image taken directly from the original 4MB mosaic. :shock:

Some of you may be wondering why this is called the Horsehead Nebula. To see why have a look at this clickable photo:
    Image
    Image Copyright © Greg Parker and Noel Carboni - many thanks to Greg for granting permission to reproduce it here.
The photograph was taken with a Sky 90 refractor telescope at f/4.5 with an SXVF-M25C colour CCD, Maxim DL for data acquisition, autoguiding, colour conversion and stacking. Over 12 hours exposure using 15 minute and 5 minute RGB subs, 1000 second H-alpha subs, over 12 hours of image processing (description courtesy of the New Forest Observatory site). By any stretch of the imagination this is serious kit and processing. The telescope can be had for around $2000. Add a top quality motorised mounting and you can probably say goodbye to twice as much again. Oh, and the camera alone costs around another $8000. Looking at that photograph (especially the full size version) it's easy to see why this object is called the Horsehead Nebula and also what around $15,000 and a great deal of skill and patience can do.

That this sort of work can be done with equipment available to the general public is both inspiring and humbling. The photograph was taken by Greg Parker and is from his New Forest Observatory site. I'll be sticking with DSLR based astrophotography but I have just ordered a copy of his book Making Beautiful Deep Sky Images and look forward, hopefully, to picking up lots of good tips.

Maybe the money I could save by going to the New Forest rather than Arizona could go towards that $15,000 equipment upgrade. :lol: :lol: :lol:

Bob.

_________________
Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


Top
 Profile  
 
 Post subject:
PostPosted: Fri Dec 28, 2007 9:54 pm 
Offline
Site Admin
User avatar

Joined: Tue Nov 08, 2005 3:32 pm
Posts: 9962
Location: Queenstown, New Zealand
Thanks for the crop Bob, and also for sharing that second shot - if you hadn't told me it was taken from England, I'd have suspected a far darker location - very impressive stuff!


Top
 Profile  
 
 Post subject:
PostPosted: Fri Dec 28, 2007 10:49 pm 
Offline
Moderator
User avatar

Joined: Sat Sep 30, 2006 4:30 pm
Posts: 9805
Location: UK
Hi Gordon,

No problem though publishing the crop was painful. It shows how much more improvement I need to make, although I do take some solace from the fact that Greg Palmer and Noel Carboni's picture contains a number of shots taken with a Hydrogen Alpha filter. Using such a narrow band filter must cancel out virtually all the local light pollution and, presumably, those shots can be post-processed separately and added to the image at a comparatively late stage.

It would be lovely to learn a little more about the post-processing that goes into producing such images, hence my decision to buy Greg's book. I am also tempted to give the Maxim DL software a free trial as it has an optional DSLR driver module which would allow full control of the 40D during an observing session in all respects other than, as far as I can see, manual remote focussing from the notebook PC. It's a bit of an industry standard for astronomical post-processing as well, I believe, but at around $500 it ain't cheap. :shock:

It's a shame that those H-alpha wavelengths are only really captured by dedicated astronomical CCD cameras or modified DSLRs with the UV/IR filter in front of the sensor replaced by clear glass. Unfortunately the cost of doing that to my 40D is about the same as buying a top lens and the camera would always have to be used with additional filters for more normal work. Of course, if the 40D were relegated as a backup camera... :P :shock: :P

Bob.

_________________
Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 146 posts ]  Go to page Previous  1, 2, 3, 4, 5, 6, 7, 8 ... 10  Next

All times are UTC


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to:  

All words, images, videos and layout, copyright 2005-2012 Gordon Laing. May not be used without permission.
/ How we test / Best Cameras / Advertising / Camera reviews / Supporting Camera Labs

Webdesign by Alphabase IT
Powered by phpBB® Forum Software © phpBB Group