From: Bruce on
On Wed, 26 May 2010 13:08:02 -0700 (PDT), infiniteMPG
<57classic(a)gmail.com> wrote:

>> Several people would have told you not to waste your money. �You might also have had some good suggestions as to how you could spend the same money on something different, but far better.
>
>Okay, let's just rewind and ask... what could I of spent my $195 that
>would of been FAR better to get me up close and personal with stuff
>that I can't capture with my Tamron 18-250???? And my "hard earned
>money" came from selling some junk I had sitting around the house on
>eBay.


I would have spent your money on a 400mm pre-set lens from the 1970s
with a T-mount adapter for your Sony A100. You could add a 2X
converter to get you to 800mm. The cost of all this? Probably less
than $100, possibly much less.

The 1970s saw many inexpensive pre-set lenses with good performance
and excellent bang for the buck. The T mount meant that they would
fit any camera. For slightly more money you could buy one with a
dedicated lens mount for your particular brand, and an automatic
diaphragm so you didn't need to stop down manually before shooting.

The results from these lenses were surprisingly good. Far better than
you will ever get with a mirror lens, almost regardless of brand.

You could even add another 2X converter to get to 1600mm, and the
results with two 2X converters would almost certainly be significantly
better than your cheap mirror lens with its 2X converter.

For the price you paid, you might also have been able to buy a Sigma,
Vivitar, Tamron or Tokina 400mm f/5.6 AF lens with Minolta AF mount.
They all give sparkling results.

If you really must buy a mirror lens, there were Vivitar solid
catadioptric lenses in 600mm and 800mm focal lengths that gave far
better results than the rest and can sometimes be found used on eBay.
They were heavy, being made of solid glass, which is why they were
optically so much better - but they were still significantly inferior
to conventional glass telephoto lenses. There were also Tamron 500mm
and Sigma 600mm mirror lenses that, while not as good as the Vivitar
solid cat, were better than most others. Minolta made one too, and a
used example might just have fitted your budget.

Possibly the best thing would be to buy the cheapest 500mm mirror lens
you could find on eBay and use it a few times. You would quickly
realise - as most of us have - why a mirror lens is not such a good
idea and you would not have wasted very much money. If you bought
used, you would probably get all your money back.

We have all made mistakes, and I have probably made more than most, so
please don't take all this as a personal criticism. I am disappointed
that you didn't ask before buying, that's all. Other people will have
different suggestions to mine and they may well be better. But by
asking, at least you would have been able to make a choice based on
the alternatives offered.

From: Kyle Abhams on
On Thu, 27 May 2010 01:26:53 +0100, Bruce <docnews2011(a)gmail.com> wrote:

>You would quickly
>realise - as most of us have - why a mirror lens is not such a good
>idea and you would not have wasted very much money

I guess that's why so many astronomers use mirror-lens configurations.

Crawl back into your hole of ignorance.

From: Bruce on
On Wed, 26 May 2010 21:40:20 -0500, Kyle Abhams <where(a)what.net>
wrote:

>On Thu, 27 May 2010 01:26:53 +0100, Bruce <docnews2011(a)gmail.com> wrote:
>
>>You would quickly
>>realise - as most of us have - why a mirror lens is not such a good
>>idea and you would not have wasted very much money
>
>I guess that's why so many astronomers use mirror-lens configurations.


That's because, at large sizes, glass lenses become impractical.

Now crawl back into your hole.
From: John McWilliams on
Bruce wrote:
> On Thu, 27 May 2010 07:19:16 -0500, Kyle Abhams <where(a)what.net>
> wrote:

drivel.


>
> Ctrl-K ...
>
> ... and peace reigns again.

And for those using Thunderbird, letter 'k' does same.....

--
john mcwilliams
From: Chris Malcolm on
infiniteMPG <57classic(a)gmail.com> wrote:

> Also, I ordered a UV filter for the 800mm as I don't like exposed
> glass and have found with the harsh bright sun in Florida a UV filter
> really cleans up many shots.

If it hasn't already got a really long deep lens hood that could make
a big difference to image contrast.

--
Chris Malcolm
Warning: none of the above is indisputable fact.