Mirror Lens?

How does this type of thing work http://cgi.ebay.com …SCC_Pr4_PcY_BIN​_Stores_IT

Poorly.

What does it do... I'm trying to understand how it works...

Optically? There are probably better links, but this will give you an idea:

http://www.skywatchert​elescope.net/Education​TBOD.html

Instead of the reflection going to an eyepiece towards the front element, it goes through a hole in the back mirror to the camera.

would this be a good buy?

DallasG wrote:
would this be a good buy?

no.

this would be a better buy.

no no say GOOD BYE to thinking about getting that brick!

Alright, I've got ~250 to spend on a lense, I've put a lot of thought into it and I've decided I want a zoom lense ranging from around 70 or 90 to 300mm, what should I get?

I'd recommend a Sigma 70-300 APO DG if your budget is $200.
Here is a review and explanation of a Tamron's version of the mirror lens.
http://bobatkins.com …phy/tutorials/m​irror.html
Sigma currently makes one for several hundred dollars, but I would not recommend those cheapo ones from ebay.

I've had alot of experience with cheap tele lenses -mirrors,'preset' types,consumer telezooms,etc
My thoughts are exactly as others have said so far-avoid the cheap mirror lenses like the plague!
If you really want a long lens (400mm ++) then there are some types of inexpensive tele lenses can give usable performance such as these -
http://cgi.ebay.com …Z4687QQrdZ1QQcm​dZViewItem

If you want a telezoom ,the sigma lens that Tee Why links is a good one -easily the most recommended consumer zoom on this forum

The sigma APO DG macro - the one with the red stripe - is optically the best of all the consumer 70-odd to 300 zooms. It's also a very good price, and would probably leave some change out of your stated budget. these lenses are good fun to play with and with care some excellnt shots can be had. they are a good way to get to learn about your camera and about technique, and in the meantime you can save for the next lens purchase.
FWIW I sold my canon 75-300 non IS because i hardly every used the 300mm, and it gave crazy camera shake, most likely due to my technique problems, buit nevertheless I didn't like it. I put the money towards the 70-200 f/4 which is optically in a different league and in terms of focal length much more hand-holdeable than a 300mm focal length. i'd suggest holding on if you can and going for better glass in the first place.
But if you can't bear to wait, the sigma is the best of all of these.

There are mirror lenses that cost 3 times as much as the one you listed which are considerably better but still prone to the problems that plague all mirrors. I do not recommend anyone buy the cheapest ones and suggest you get quite a bit of experience using more normal gear before considering even one of the better ones. The Russian models are better as is the Sigma but none are L glass!
My Sigma mirror gallery:
http://www.pbase.com/d​ougsmit/sigma600

I used to have a Tamron SP 350 f5.6 mirror - I've never seen another copy, but I loved it. Yes, it had all the characteristics of mirrors as described above, but it was insanely sharp and did good macro. Also, it was fast enough and light enough to easily hand-hold. I personally don't have any use for a 500mm, so I've never looked at those.

Hey guys, don't be so negative about this type of lens.
Here we have a fellow photographer who wants a "big" lens for as little money as possible and who can blame him?
For 20 years I used a Canon 500mm reflex-lens (a Maksutov-Cassegrain-lens to call it exact) on a Canon A-1 body with great succes.
The only difference, and I call it a big advantage, nowadays in the digital world is the fact that one doesn't need to put in a 1000 iso or even a 1600 iso-film to be able to shoot a single picture.
With the use of an adaptor for the EOS mount I'm using this mirror lens on several occasions and going for a setting of 400 iso and less. The pictures are tack sharp and in need of a little contrast enhancement but that's all there is.
Of course there are limits to consider. Flying birds are as good as out of the question and the smaller viewer on a 350d doesn't help eighter. In short it is a difficult lens to handle. But hey it's a damn fine piece of glass and the lady is made in 1980. I use those pictures next to the ones taken with my 300mmL-lens so that's something to think about.
Now back to the DallasG-question.
Since I had this lens in a previous life, I kept it in use today. It sure is not a lens to recommend because of the single fact that it has no autofocus.
The mirror lens will provide you good supertele photos for little money but soon you'll want an autofocus.
So the next best thing is to go with the idea of Tee Why (70-300).
Alain
---------------
Canon 350d - Sigma 18-200 - Canon 300USM L IS - Canon 500 reflex - Canon 1,4II extender

I used to love my Tamron 500 mirror! Macro shots from 6 feet
away were so cool. The only thing that I didn't like was the
doughnut bokah. Perhaps they don't work as well in digital as
they did on my AE-1