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PostPosted: Sun Jul 22, 2007 10:28 pm 
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Hmmm, teleconverters... I hadn't thought of testing them, but could do in the future. The trouble is deciding which lenses to test them with, as each combo would represent the same testing workload as a separate lens.

So it could be very time consuming...

Let me know what sort of converter plus lens combos you'd be interested in though and I'll have a think...

As for the Canon 85mm f1.8, I can certainly vouch for its quality - it's a great lens, and great value too...

Gordon


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 Post subject: Teleconverter Testing
PostPosted: Mon Jul 23, 2007 12:33 am 
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Gordon wrote:
Let me know what sort of converter plus lens combos you'd be interested in though and I'll have a think...

Hi Gordon,

I am beginning to wonder if Canon extenders (their name for teleconverters) are a suitable candidate for review!

Canon extenders are only compatible with selected lenses. Unless one already has a compatible lens it seems to me that one can only achieve a significant cost saving by buying a lens and an extender together if the target focal length is longer than 400mm which is pretty specialised stuff given an outlay of around £1000/€1500/US$2000.

That said, if you would like to review the excellent EF 70-200mm f/4L IS USM in conjunction with a 1.4x extender you might guess from my profile that I would be more than happy. 8)

Bob.

P.S. My previous post where I considered the inadvisability of pairing the Canon EF 85mm f/1.8 USM was irrelevant as that lens isn't on the compatibility list.

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PostPosted: Mon Jul 23, 2007 6:47 am 
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The Nikon AF 80-200mm 2.8D ED VR or AF 80-200mm 2.8D ED are certainly also excellent candidates, but only reach to 280/340mm with 1.4x/1.7x converters. Both were not yet tested with tele-converters.

The other thing: Is IS really working ok with a teleconverter or are you losing much of the benefit?!

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Last edited by Thomas on Tue Jul 31, 2007 6:37 pm, edited 1 time in total.

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PostPosted: Sun Jul 29, 2007 12:57 pm 
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With regard to the "real" aperture of this lens I took some measurements and did some calculations:
- diameter of entrance pupil: 77mm
- diameter of front mirror: 36mm
That gives an area A of the entrance pupil of PI*((77/2)^2-(36/2)^2)=3639mm²
The equivalent diameter D of a „normal" entrance pupil (w/o front-mirror) then calculates as sqare-root(A/PI)*2 = 68mm
This in turn gives a calculated aperture of F=500/68=7.4. And with 8% loss caused by the mirrors you'll end up at an effective aperture of F8,0!
The aperture that is relevant for dof is F*=500/77=6.5.

But Klaus was not convinced. He questioned whether the back-mirror was fully used...

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 Post subject: Effective aperture
PostPosted: Sun Jul 29, 2007 1:28 pm 
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Thomas wrote:
But Klaus was not convinced. He questioned whether the back-mirror was fully used...


Is his concern related to vignetting?

Bob.

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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.


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 Post subject:
PostPosted: Sun Jul 29, 2007 1:33 pm 
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No. Vignetting is absolutely minimal on this lens. He was thinking that perhaps the extreme outer border of the back-mirror was not used due to adverse optical effects from manufacturing and/or mounting.
But then, as there is actually a frontlens in this construction that should already make the incoming rays convergent and not make them hit the outer border.

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 Post subject:
PostPosted: Sun Sep 09, 2007 1:25 pm 
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Bob, with regard to Ken Rockwell's testing of IS/VR:
After having had the Nikon VR 80-400mm in my hand I can say VR works, but this VR is really not too impressive. At 400mm I get a lot of fails at 1/60sec and mostly good ones at 1/90sec (but still some fails). So perhaps Ken's 1/250 is a bit pessimistic (or I'm more sedate than Ken), but still I had expect more than just 2 shutter-stops stabilization.
Seems this lens is showing its age :?
I'll report in greater detail here, as soon as I have the time for posting.

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PostPosted: Sun Sep 30, 2007 3:35 pm 
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Well, now other tests have confirmed that the VR-capabilities of the Nikon VR 80-400mm leave a lot to be desired (see here and there). So if you're after a longer affordable tele-zoom for Nikon with a good working IS, take the VR 70-300mm. It's easier to crop a 300mm shot that is sharp through both the optics and very low shake to 500mm equivalent than to make an optically sharp, no-shake, in-focus 500mm shot with the Tamron 500mm.
But it can be done! I've been out this morning to an airfield where a glider-contest was being carried out. With my 500mm mirror lens at ISO 1600 (!) and 1/2000 sec I managed to get some sharp shots. And this although the gliders were moving pretty fast and I was manually focussing :D
Enjoy the following shots (with just a little postprocessing):

Landing approach:
Image

Just before touch-down:
Image

Preparing for take-off:
Image

Again, I'm very content with the ISO-1600 capabilities of the D80 body.
See some more shot here.

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Last edited by Thomas on Wed Oct 03, 2007 5:22 am, edited 2 times in total.

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 Post subject:
PostPosted: Sun Sep 30, 2007 11:12 pm 
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That first shot is ace Thomas!


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 Post subject:
PostPosted: Mon Oct 01, 2007 6:13 am 
Great Shot Thomas!
As Gordon mentioned the 1st once Aced it.


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PostPosted: Mon Oct 01, 2007 7:50 pm 
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Thanks guys!
I love the first shot too! Have you noticed that the fuselage reflects the surrounding landscape (a green meadow and dark wood - look under the wing) :)

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 Post subject:
PostPosted: Mon Oct 01, 2007 9:02 pm 
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I just think when you capture the expression and facial details of the pilot from OUTSIDE the aircraft, you're onto a winner!

Note to self: must get telescope out during the day...! (only kidding, you can't see the pilot's mustache on a commercial plane, but you can see a lot of external fuselage detail when viewing through a scope...)


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 Post subject:
PostPosted: Mon Oct 01, 2007 9:37 pm 
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Yeah, he was almost "into my face" :D
Btw in case you hadn't noticed: #2 is still in the air (2m above ground), shortly before touch-down.

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 Post subject:
PostPosted: Thu Oct 04, 2007 9:37 pm 
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I owe you folks still one on this lens: The Siemens-star.
Well here it is, unfortunately only the 1:10 version at 5m, because the room was not large enough to step back any more. Perhaps good weather permitting I'll hit the garden and make at least a 10m/1:20 shot next weekend. We'll see...
Image
You'll have to click through to the large original to measure it all by yourself or you can believe me that the grey disk is around 15-20mm on this lens. Which is about half the resolution of what my other lenses do.
I'll also get my VR 18-200mm out and add some "scientific" resolution-measurement to this thread. So we can compare whether a shot at 200mm suitably magnified is better or worse than the original 500mm resolution.

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Last edited by Thomas on Thu Oct 04, 2007 10:31 pm, edited 1 time in total.

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 Post subject:
PostPosted: Thu Oct 04, 2007 10:31 pm 
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Mission complete: added the 18-200mm test-shots at 200 f8 here to understand how much you can get out of the super-zoom when you compare it to the 500mm mirror-lens.
So here is the result: centre-resolution of the 18-200@200mm/f8 is about double that of the Tamron 500mm. So roughly speaking you could zoom up the 200mm-shot in post-processing 2 times to get an equivalent 400mm-shot with a similar resolution to the Tamron 500mm.
But don't forget: AF and VR on the Nikon 18-200mm@200mm will add a reliability to the shots you make with this lens, that the 500mm mirror-lens sorely lacks :(
If you really want sharp super-tele shots go for the VR 70-300mm (see Gordon's test here) or the VR 80-400mm (see my review there).

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