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Old Jun 23, 2004, 12:01 AM   #1
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Just a couple of our barn pigeons displaying for the horses and other birds :-)

Canon 10D - Swarovski ST-80HD at 1280mm

Lin




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Old Jun 23, 2004, 10:11 AM   #2
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Hi Lin

Nice shots.

I prefer to call them Rock Doves, or "some kind of plovers." :-)

Where does the 1280mm figure come from? I didn't know Swarovski made such an adapter.

Dave
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Old Jun 23, 2004, 11:09 AM   #3
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Hi Dave,

Swarovski actually makes two 35mm platfom adapters,one is 800mm and the other 1100mm. Because

of the Canon 10D 1.6x reduced field of view, you get a 60 percent electronic focal length addition which

makes the 800mm adapter function at 1280mm (800x1.6=1280) equivalency. With my 1DS it functions as

800mm and with my 1D, 1D Mark II and Kodak DCS-760 it's 1040mm (800x1.3=1040). With

the Swarovski astro eyepiece adapter you can use any 1.25" celestial telescope eyepiece afocal with the

little CP series Nikons (I use the CP950, 990 and 4500) and get up to 7000mm or so of usable focal length.

Best regards,

Lin

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Old Jun 23, 2004, 12:06 PM   #4
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Nice shots Lin,

One bird appears to have grey eyes and the other brown? There are some similar wild pigeons living near me although

I have not yettried to photograph them.



Since this is with the 10D did you crop this much? Are youlimited toafixed focal length with the SLRs but able to use the

zoom eyepiece with the Coolpix? You seem to have a veryimpressivecamera collection.



Dog Dave

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Old Jun 23, 2004, 12:27 PM   #5
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Hi Dave,

No crops, I just reduced to 800x533 for screen display. Yes the focal length is fixed with the Swarovski

and any SLR but as you assume, since the Nikons are shooting through the eyepiece of the scope, they have

the full use not only of their zoom range but also all electronics (autofocus, metering, aperture, etc.) available.

This is why digiscoping is really "better" with the fixed lens Nikon CP's than with dSLR's or SLR's.

Best regards,

Lin

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Old Jun 26, 2004, 9:18 AM   #6
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Lin Evans wrote:
[quote]Hi Dave,

Swarovski actually makes two 35mm platfom adapters, one is 800mm and the other 1100mm. Because

of the Canon 10D 1.6x reduced field of view, you get a 60 percent electronic focal length addition which

makes the 800mm adapter function at 1280mm (800x1.6=1280) equivalency. With my 1DS it functions as

LOL! Well, yes an no. I have both adapters, mainly use the 800. However, while you get the benefit of additional pixels, you are not actually CLOSER to the target - In other words you are 22 times closer with additional pixels. Sorry for beating a dead horse - I appreciate the cropping factor but...

Dave
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Old Jun 26, 2004, 10:39 AM   #7
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Quote:
LOL! Well, yes an no. I have both adapters, mainly use the 800. However, while you get the benefit of additional pixels,
Quote:
you are not actually CLOSER to the target - In other words you are 22 times closer with additional pixels
Quote:
. Sorry for beating a dead horse - I appreciate the cropping factor but...


Hi Dave,

Sorry, I'm not quite following what you're saying. If you are wondering about the focal length issue let me try and explain it.

The true focal length is, of course, 800mm. But the term "cropping factor" is a misnomer. So called "crop factor" sensors

function differently than a true "crop" in the photographic sense. Whever you crop a capture, whether it be from a film platform

or from a digital capture, you loose enlargement potential. Let's take a 35mm film example and see how this works. Let's say

the enlargement potential for a 35mm film capture is 16x24. Take a 35mm negative and cut it in half on the long axis to "simulate" a crop

and the enlargement potential of what is left is now 12x16 for each half. So if we indeed "crop" a 35mm full frame capture to the same

frame as a 1.6x reduced field of view sensor capture we loose 60 percent of the enlargeability whether that crop was from an

11 megapixel 1D capture, a 14 megapixel 14n capture or a 35mm transparency or negative.

On the other hand, with a "crop factor" sensor, we actually "sample" this reduced field of view with the full resolution of the sensor.

Because we vest the entire "resolution" within this reduced field of view, and because pixels are simply numeric coefficients at

this stage, when these numeric values are converted to display or print pixels they produce a full resolution display containing

information identical in size or "magnification" to what we would have had if the capture had been made with a full frame sensor

or 35mm negative captured with a 60 percent longer focal length. The aspects of depth of field and other characteristics imparted

by the optics are, of course, germain to the actual lens used, but the "magnification" has been performed electronically via the sampling

of the smaller field of view so the "effective" focal length is identical to what we would have had if we had used a lens of 60 percent

greater focal length with a full frame sensor from the identical location.

There has been too much confusion about this issue primarilyfrom those with a background in film and because of the poorly

advised term"crop factor" used to describe the event. It's indeed a different issue from the physics perspective.


Dog Dave:


Yes, I do have lots of equipment both film and digital including 5 Canon dSLR's representing all platforms, a Kodak six megapixel

dSLR,MF digial backsand a couple dozen fixed lens digicams. I shoot all platforms both digital and film, but these days use primarily

digitalprofessionally.

Best regards,

Lin




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Old Jun 26, 2004, 1:04 PM   #8
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Lin wrote:

"Yes, I do have lots of equipment both film and digital including 5 Canon dSLR's representing all platforms, a Kodak six megapixel

dSLR,MF digial backsand a couple dozen fixed lens digicams. I shoot all platforms both digital and film, but these days use primarilydigitalprofessionally.

Best regards,"



Yikes, so you are a pro photographer then... either that or a retiredorthodontist.Am I correct thenthat the SLR's mount directly to

a fixed adapter and thusprovide noopportunity for zoom?


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Old Jun 26, 2004, 1:20 PM   #9
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Yes, at least the way the Swarovski mount works. Also with a camera port on the

Mead, Celestron or other reflector scopes the scope acts like a prime lens with no

ability to zoom.

ScopeTronix just released a couple eyepiece projection adapters for 1.25 and 2.00

inch eyepieces. If the eyepieces are zoom types, then it would appear that it's possible to use the scope's zoom ability

to shoot afocal with a 35mm platform. I haven't had the opportunity to try it yet

so can't say how well it might work, but it does give the possibility of greater focal

length than with the native focal length of the tube itself (such as 1250 mm with the

Meade, etc.) Here's a link to the ScopeTronix site to check it out:

http://www.scopetronix.com/

Best regards,

Lin
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Old Jun 27, 2004, 8:00 AM   #10
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Hi Lin

This is a tricky topic. I don't want to seem in the position of denying the usefulness of the crop factor. I fully understand the benefit

of more pixels being on the target.

So the cropping factor in some ways approximates a true zoom. However in some ways it doesn't.

If you are 22 times closer to the target you resolve a certain amount of detail - That resolved detail is enhanced by the additional pixels

which the cropping factor supplys.

However if you are 26 times closer to the target additional detail are resolved simply be actually being closer. There is a trade off here.

All things being equal (which they are not) I would rather be closer to my target with a true zoom then with an increased number of pixels.

Or in other words, assuming the same number of pixels (produced by a full frame sensor that matches the number of pixels on a 1.3

sensor on the target) the true zoom will be better then the cropping factor zoom - even though the number of pixels is the same.

Dave


Hi Dave,

I understand your position, and in some ways agree, but there are a couple

considerations we need to investigate. First is the "being closer to the target".

As you know, optical magnification works by using convex and concave lenses

to gather, bend and focus light. This gives a "virtual" illusion of being closer to

the subject, but is not the same as indeed "being closer" to the subject. The

operantterm here is "gather light" so that this virtual effect lets us examine

the subject "as if" it were closer to our eyes. Optical magnification is a very good

way of apparently bringing the distant world closer to us.



Electronic magnification works differently in the relevant sense by breaking down

the already optically magnifiedimage into small, discrete, digital representations

of this light which are then "reverse" engineered to produce tiny squares of "real estate"

which are assembled into a visual representation of the whole either on screen or

on a piece of paper. By providing an increasing number of sampling sites, we achieve

greater discrimination of this real estate being sampled which results ultimately in

an image which somewhat resembles the original as our eyes might have seen it

from a closer vantage point.To some as yet undetermined limit, we canovercome

diffraction and separate discretedistant objects to some measured resolution.



The issue of optical magnification versus electronic magnification has yet to be completely

investigated, but in my experience using a wide variety of optics and cameras, I see little

practical difference within the present limits of digital evolution. Unfortunately there is no good way

at present to testour "impressions" about this becauseour only available full frame instruments

have highersampling site(resolution) counts than the "crop factor" alternatives with the exception

of the Contax six megapixelcamera which I don't have available. But one waywe can get close

is to examine resolution charts and see that there is little or no realistic difference between

the 1.3x, 1.5x, 1.6x and 1.7x "crop factor" sensorsin terms of resolving ability. That is in measured

tests, the"crop factor" cameras perform equal to or better than the Contax full frame sensor.

This would appear to indicate thatwithin the present state of technology, there is little or no

true difference betweenthe resolving ability of a crop factor sensor at 1.X and a full frame sensor using

optical magnificationto equal the crop. In my practical experience I find this to be true.

How this will eventually play out in practice, of course, remains yet to be seen.



Best regards,



Lin

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