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Posts Made By: Alan Birnbaum

June 17, 2003 10:20 PM Forum: Birding Optics and Photos

Sigma markets stabilized zoom lens

Posted By Alan Birnbaum

One more option for those looking for a 80/100 to 400 stabilized zoom lens will come from Sigma:

http://www.sigmaphoto.com/Html/news/80-400os.htm

Their 7.5" long, 58 oz. version closely parallels the Nikon offering, as both are f4.5-5.6. The Sigma will sell for about 30% less than the Nikon. An interesting question will be whether its mechanism will allow the stabilization to be used on older Nikon/Canon bodies. It is of course at least twice the price and a pound heavier than the earlier Sigma 135-400 zoom lens.

June 21, 2003 03:12 AM Forum: Birding Optics and Photos

Celestron C5: F-stop vs. T-stop

Posted By Alan Birnbaum

I pose this question mainly for Tyler Allred, who has actively been using a D100 with both conventional photo lenses, such as the Nikon 70-300/4-5.6, and the Celestron C5, most commonly with the 0.63 reducer that converts the native F10 Schmidt-Cassegrain to f6.3.

F-stop vs. T-stop refers to the relative light transmission. I.e., a lens that is very inefficient, letting through only half the light supposedly it should, would have a T(ransmission)-stop of f8, if the native lens by aperture was f5.6.

So, same scene, say bright sunlight, where at an ISO 100 setting you'd expect the 70-300/4-5.6 to result in an exposure of 1/800, and the f6.3 C5 to give an exposure of 1/640, what is the ACTUAL exposure typically indicated by the D100 for the C5?

Due to the light loss from reflecting off the primary and secondary mirrors, as well as the effect of the central obstruction, I know it has to be slower, but, I'm interested in how much slower, than the 1/640, which allows one to calculate the T-stop of the lens.

Once Tyler has a chance to respond, I'll relate further my experience today shooting a roll of ISO 400 film with a vintage 1983 Sigma 600 mm f8 "mirror" lens, trying to get some shots of a Mute Swan (who likely had escaped from someone's private pond.)

June 24, 2003 03:32 PM Forum: Birding Optics and Photos

Olympus E-1 becoming available

Posted By Alan Birnbaum

Those looking for a digital imaging system may want to take a brief look at the new Olympus E-1 "4/3" SLR system:

http://www.dpreview.com/

For wildlife imaging, the critical lens in the system is the $1200 50-200/2.8-3.5 zoom lens, equivalent to a 100-400 lens on a 35 mm camera. BUT, as the lens is NOT image stabilized, I suspect that those interested in flight photography will prefer to stick with the Canon system, where the 100-400 IS lens, while somewhat slower, is stabilized, and the equivalent FL 160-640, or the Nikon system, with its 80-400VR lens that is equivalent to 150-600. And, both of these systems also offer a 70-200/2.8 image stabilized lens.

At 24 ounces, the E-1 body looks to be much to heavy to adapt to routine digiscoping, I'd think. There is also a 300/2.8 (equivalent to 600/2.8) telephoto, along witha 1.4X converter available for it. If you used one to look down the block at the price tag on a second example, you would be able to clearly see and record "$7999." The announced price of the E-1 body itself is for now higher than the Canon EOS-10D, or the Nikon D100. Overall, I would predict only a brief look from the wildlife imaging set.


July 10, 2003 03:09 PM Forum: Equipment Talk

Orion Ultraview 10x50

Posted By Alan Birnbaum

I received two pair of the Orion Utraview 10x50 porroprism binocular yesterday, one actually being bought by one of my employees, the other intended as a birthday gift for my brother-in-law (who hopefully does NOT read this board!)

For anyone who does not yet have, or needs to recommend to a friend a basic binocular for astronomy, these are clearly a good choice. Build quality is quite good, the apparent field of view does appear to be 60°, the eyecups work nicely, and the eye relief is very generous. They feel good in the hand, with a nice wide diamond pattern knurled focus ring.

Personally, I think Orion should leave out the four individual ocular and objective caps, in favor of a single rainguard that can be attached to the very adequate neckstrap, but otherwise, for now these have become my primary recommendation for anyone who wants a moderately-priced basic binocular for astronomy, or, for terrestrial work, where a slightly heavier unit would not pose a problem.

July 22, 2003 04:17 PM Forum: Equipment Talk

Nikkor 200-400/4 VR lens announced

Posted By Alan Birnbaum

For those of you with the muscles and the budget to afford it, Nikon has just announced a new 200-400/4 VR lens, equivalent to 300-600 for the digital models. The advantage would of course be the additional shutter speed at the upper end of the range, 1/500 vs 1/250 and the like. The lens has some additional innovative features of interest, including preset focusing positions, apparently done electronically.

August 3, 2003 12:10 AM Forum: Equipment Talk

adverse report on Swarovski ATS65

Posted By Alan Birnbaum

This was an alarming report I came across, from someone who had used the Swarovski ATS65 during a birding trip to Gambia:

<
MC had the new Swarovski ATS65 scope which disintegrated on the penultimate day. First the swivelling ring went, then the focussing and finally the tripod mounting bracket broke off. In Lesbos, a year ago, the eye-piece fell out, which also happened, on this holiday, to the birder in the next room to ours. This optically superb instrument appears to be mechanically unsound. It would be interesting to know if any other birders have had similar problems.>>

Source is:

http://mysite.freeserve.com/birdingtrips/trip_report_2003.htm

I certainly hope this was an isolated experience! It does look as though the tripod foot on the ATS65 is some sort of plastic, rather than metal. If the tripod mount broke, this would adversely affect the helical focuser, which is immediately in front of it. I may contact the source, and find out what happened to the scope, as far as warranty and service.


August 5, 2003 03:38 PM Forum: Equipment Talk

Bogen #3157N mounting plate is unidirectional

Posted By Alan Birnbaum

It appears to me that the Bogen-Manfrotto small rectangular mounting plate, #3157N, is UNIDIRECTIONAL. Always check the bottom of the plate to make sure you install it correctly. If you place it onto your spotting scope or binocular mount backwards, the Bogen Junior or the #3130Q head allows definite play, which could introduce undesired vibration or worse, risk of unintentional detachment.

I noticed such this morning, while experimenting with my Swarovski ATS65 HD, whose foot will fit directly into these mounts, with and without the plate, determining that if I used the plate, in one direction is was very snug, but reversed, the mounting jiggled. For someone digiscoping, this could degrade images.

The bottom of the plate, which I believe was redesigned a year or so ago, clearly has arrows showing the correct direction. But, I'm not sure that the instructions point out this small but potentially critical matter.

August 17, 2003 05:12 PM Forum: Birding Optics and Photos

Sony DSC-F828 7X zoom, 8 megapixel camera

Posted By Alan Birnbaum

Seeing that Sony has just announced what seems to be the most advanced of the so-called "prosumer" digital cameras:

http://www.steves-digicams.com/2003_reviews/f828.html

the 7X, 8 megapixel, DSC-F828, what might its potential be for use in digiscoping, based upon any known such use of the vaguely similar predecessor model, the DSC-F717, which had a 5X zoom, and a similar physical configuration?

On the plus side, it looks as though this camera may have a lens that zooms internally, obviating some of the front element to front element clearance variation issues. On the other hand, its fairly heavy, likely about as much as a digital SLR plus normal lens.

It does look as though any such use might depend upon getting a custom bracket fabricated for it, facilitated by the tripod mount for the unit being on the underside of the lens assembly, not the swiveling viewfinder section.

Alan Birnbaum
Fresno, CA

October 20, 2003 05:14 PM Forum: Equipment Talk

of arcseconds and the NEED to know

Posted By Alan Birnbaum

I've re-read some of Steven Ingraham's articles from "Better View Desired." In particular I note his use of "NEED" measurements to quantify resolution in binoculars of various types and powers. His figures for the Nikon Superior E in the 8 x 32 are worth noting, as they compare to some 8 x 42 models. NEED seems to have superceded his earlier use of arcsecond resolution figures.

For those unfamiliar with it, a "NEED" figure represents the distance, in feet, at which one can determine that a certain "gray" tone on the back of a dollar bill is actually a series of closely spaced lines. 16 feet or so for an 8X is typical, the Nikon SE 8 x 32 does 18 feet, while the Nikon 10 x 42 SE are in the 22+ foot range. (Ed Zarenski would likely have us note that the 20% improvement can be explained by magnification alone.)

That the very best Nikon SE 10 x 42 can resolve 3.58 arcseconds is of interest, i.e., it can split a single degree into more than a thousand parts. So is his determination that a Zeiss 7x42 can do 4.50 arseconds, a split of that degree into 800 parts. But, the NEED, which is much easier done, seems more real world. (And its hard to beat the price of that government-engraved resolution target!)

Perhaps some of the debate on this web page might benefit from the illumination of actual testing, and real data. Wouldn't it be interesting for someone with access to, say, the Nikon Venturer LX in both the 8 x 42 and the 8 x 32, provide some results? Or perhaps the Swarovski EL 10 x 42 vs. the just announced 10 x 32?

Maybe we don't really NEED to know, but when it comes to arguments, might not FACT be better than FRICTION!?

November 22, 2003 04:20 PM Forum: Birding Optics and Photos

Panasonic Lumix DMC-FZ10

Posted By Alan Birnbaum

See:

http://www.steves-digicams.com/2003_reviews/fz10_pg5.html

Here's an interesting option for someone who might want to do some casual digital bird photography, with equipment under $600, in a camera weighing only about 20 oz.

With a IMAGE-STABILIZED 12X zoom that tops out an an equivalent FL of 420 mm, this edges into the range useful for bird photography, and even at that level offers f2.8. Of course, this has a SMALL sensor, 1/2.5, barely larger than that found in most pocket 3X cameras, but still that will do some work.

Otherwise the least expensive option would be a digital SLR, body alone $900 to $1500, image stabilized 80-400 or 100-400 zoom doubling that, for a total investment of $2500 to $3.000, and a LOT heavier.

As the lens reported has moderate barrel distortion at the wide angle end, likely the camera might not make a great overall camera, but at the 140-420 EFL where it would be used, it might well be all many folks want or need.