Blown away by a scope

[Keebert]

Yesterday, I was at a local nature center and we were looking out into jungle taking photos. I mentioned to the guide that I had not seen any parrots yet and he pulled out this Leica scope on a tripod and dialed it in. This is the first time I have looked through a scope like this and I was blown away.

Firstly, the level of detail and clarity of the scope was amazing - we were looking at a parrot that was probably half a mile away but I could see feathers and great detail.

Secondly, there was this almost 3d like quality to the picture which I have never seen looking through a camera lens.

So what's going on here? How come these scopes give such a good picture in a relatively economic package (compared to a long L)? Is my eye ISO gazillion which is why the scope doesn't have to catch so much light?

I tried to take a photo but it's pathetic in comparison to what was seen by the scope:



100%

[weeatmice]

They have smaller apertures compared to telephoto lenses - less glass. They are also fixed, no aperture blades. No autofocus. No idea how they compare optically but I'd guess those things explain the cost difference.

[yoss1138]

Originally Posted by Keebert

So what's going on here? How come these scopes give such a good picture in a relatively economic package (compared to a long L)? Is my eye ISO gazillion which is why the scope doesn't have to catch so much light?

The view through a 400mm lens feels like roughly 8x magnification. A Leica scope will have a 25-50x magnification eyepiece and probably shows excellent brightness and detail all the way to 40x. That's directly to your eye, no sensor, no cropping.

[Joe Ravenstein]

Wow! If not for your 100% crop image I'd never have seen the parrot or even know where to look.

[Keebert]

Originally Posted by yoss1138

The view through a 400mm lens feels like roughly 8x magnification. A Leica scope will have a 25-50x magnification eyepiece and probably shows excellent brightness and detail all the way to 40x. That's directly to your eye, no sensor, no cropping.

Why can't they do this with camera lenses then? I'm trying to understand what the limitation is that stops us from having such reach.

Originally Posted by Joe Ravenstein

Wow! If not for your 100% crop image I'd never have seen the parrot or even know where to look.

Can you imagine - that was a shot with a 400mm so already enlarged. These guides have an incredible skill in picking out these birds from the vegetation.

[Foggiest]

Originally Posted by Keebert

Why can't they do this with camera lenses then? I'm trying to understand what the limitation is that stops us from having such reach.

The f number is worked out by focal length divided by aperture ......

So 400mm with a 100mm front element is f4 ...... now as nothing is perfect , you tend to end up with a slightly larger front element to compensate for real life losses in the system .
IE the 400mm F5.6 has front element of around 77mm .

So if a 400mm gives 8 mag and you want 25 mag ... then ... 1250 mm focal length .
If you want maximum aperture of F4 then the front element will have to be over 312mm (probably over 500mm).
This is where you start to get to the limits of cost and production problems .
IE mega money for huge ass lenses

[Keebert]

OK, so say the scope is 1250mm f/11 or something that gives you a sane front element - why doesn't anyone make lenses like this? Clearly people are making the scopes with this capability, why not put a sensor behind it?

[Hot Bob]

The exit pupil of a high magnification scope is very, very small, around 4-6mm. In order to replicate that view in a lens, the exit pupil would need to be hundreds of times larger to completely cover a sensor. Now multiply the size of the scope you were looking through by several hundred and you will see why it is not practical.

Bob

[monty28428]

Look up digiscoping -- lot's of folks use scope to take photos - some better than others.

[Keebert]

Originally Posted by Hot Bob

The exit pupil of a high magnification scope is very, very small, around 4-6mm. In order to replicate that view in a lens, the exit pupil would need to be hundreds of times larger to completely cover a sensor. Now multiply the size of the scope you were looking through by several hundred and you will see why it is not practical.

Bob

Eeek... f/250? That explains a lot...

[mhrok]

Heh.. technically there is no limit as to the size of your lens. However, for us mortals there is. BUT, if you are a sheikh in Qatar, you get personal assistants and special treatment even at Zeiss.

This is old news, but here is the 1700mm f/4 with image coverage for a medium format Hasselblad:

http://www.dpreview.com/news/2006/10/1/zeiss1700f4

And think that people here call Sigma 200-500 f/2.8 a monster..

The petrodollar-filled Qatari wanted it for "bird photography" with "the best possible image quality".. so got this ridiculous lens that weights 256 kg. However, I highly doubt it will ever be used for taking bird photos -- like the car collection of Sultan of Brunei probably is never taken to a race track, just sits there for show.