Go Back   Steve's Digicams Forums > Digital SLR and Interchangeable Lens Cameras > Sony Alpha dSLR / Konica Minolta dSLR, Sony SLT

Reply
 
Thread Tools Search this Thread
Old Jul 25, 2009, 5:30 PM   #1
Member
 
Join Date: Jun 2009
Location: Lancashire, UK
Posts: 41
Default cheap 500mm mirror or 2x convertor

Ok folks I'm after a cheap way of getting a long focul length?
there are a good few cheapish 500 mm mirror lenses available for around the 120 mark, or would i be better buying say a 1.4x convertor to use with my Tamron 70 - 300mm zoom I recently bought ? i know the mirror is fixed at f8 anyway so how many stops would i loose with a convertor ?
Tazkb is offline   Reply With Quote
Sponsored Links
Old Jul 25, 2009, 6:42 PM   #2
Senior Member
 
TCav's Avatar
 
Join Date: Sep 2005
Location: Washington, DC, Metro Area, Maryland
Posts: 13,572
Default

A 1.4X TC will reduce the maximum aperture by 1 f-stop.

And while the Tamron 70-300 Di LD is a nice lens for not a lot of money, a TC will magnify the flaws, and throw in some of its own.

I have 1.4X and 1.5X TCs that I picked up off eBay for less than $50 each, and have been more pleased with them than I had been with a Quantaray 2.0X TC that I started calling "The Purple Fringe Machine." A major difference between them is that the 1.4X TC is chipped and the 1.5X TC isn't. That means that the camera gets the corrected focal length and aperture when I use the 1.4X TC but doesn't when I use the 1.5X TC. If you use a slow lens (like your 70-300) with a chipped TC, you can't autofocus at the long end, but with an unchipped TC, any lens that autofocuses without it will autofocus with it, but since the camera has the wrong focal length, the image stabilization won't properly compensate for camera shake. All 2.0X TCs are chipped, but few 1.4X TCs are.

On the other hand, unless you go with the Sony (Minolta) 500/8 Reflex lens, you won't autofocus anyway, and the image stabilization really won't properly compensate for camera shake. Plus, you'll only be able to shoot in M Mode. Catadiotric lenses are small, light, inexpensive, and provide good image quality (probably better than you'll get with your 70-300 and a 1.4X TC), but you give up a lot when you choose that route.
__________________
  • The lens is the thing.
  • 'Full Frame' is the new 'Medium Format'.
  • "One good test is worth a thousand expert opinions." - Tex Johnston, Boeing 707 test pilot.

Last edited by TCav; Jul 25, 2009 at 6:45 PM.
TCav is offline   Reply With Quote
Old Jul 25, 2009, 7:54 PM   #3
Member
 
Join Date: Jun 2009
Location: Lancashire, UK
Posts: 41
Default

so which is it to be then ? or which route would you take ? i'm still not sure whether to go for the cheap 500mm cat lens like this one
http://cgi.ebay.co.uk/Opteka-500mm-f...3A1%7C294%3A50
or go the 1.4x convertor route ?
Tazkb is offline   Reply With Quote
Old Jul 25, 2009, 7:58 PM   #4
Member
 
Join Date: Jun 2009
Location: Lancashire, UK
Posts: 41
Default

i forgot to add that particular lens is offering F6.3 not the usuall F8 which make's me think it will be a better bet, I know it's not going to compete with $1000 + lens's but unless i win the lottery my bank balance won't come near them either, for what I need it will surfice, is the extra F stops found here with this F6.3 500mm give me much better resolution than the F8 models ?
Tazkb is offline   Reply With Quote
Old Jul 25, 2009, 8:01 PM   #5
Member
 
Join Date: Jun 2009
Location: Lancashire, UK
Posts: 41
Default

mind you I also saw this advertised as well
http://cgi.ebay.co.uk/500mm-f-8-0-Le...3A1%7C294%3A50
however I feel the cat lens will probably be of better quality, what do you think ?
has anyone any real experiance of these cheaper long lens's ?
Tazkb is offline   Reply With Quote
Old Jul 25, 2009, 9:13 PM   #6
Senior Member
 
TCav's Avatar
 
Join Date: Sep 2005
Location: Washington, DC, Metro Area, Maryland
Posts: 13,572
Default

I was actually looking at the catadioptric lens myself.

Between the catadioptric lens and the refractive lens, I'd pick the cat. It has fewer polished surfaces so it will probably be sharper, and there isn't a lot of refracting going on, so there will probably be a lot less chromatic aberration.

But an f/6.3 cat lens will have larger polished surfaces than an f/8.0, and for one f-stop, you'll probably lose some image quality.

But would I put a 1.4X TC on a Tamron 70-300 Di LD, or go with a cat?

Hmmmm...

The TC will be cheaper.
The cat will probably give better image quality.
The TC will give me AE and maybe even AF.
The TC may even let me shoot handheld, while the cat will have to be supported. (tripod, etc.)

If I were doing long exposures or astrophotography, where I'd use a tripod anyway, I'd go with the cat.

If I were going birding on a budget, I'd get the TC. (Your choice whether it's chipped or not.)
__________________
  • The lens is the thing.
  • 'Full Frame' is the new 'Medium Format'.
  • "One good test is worth a thousand expert opinions." - Tex Johnston, Boeing 707 test pilot.
TCav is offline   Reply With Quote
Old Jul 25, 2009, 10:35 PM   #7
Member
 
Join Date: Jun 2009
Location: Lancashire, UK
Posts: 41
Default

yeah you have kind of mirrored my thought's exactley, the trouble is it's one or the other (i suppose idealy buying both would be good) and i need to act sharpish before my lovley wife finds my small savings stash and finds some thing "more usefull" to spend it on. I useually use a tripod for most of my shots even wildlife, or if not a tripod some sort of rest as i'm disabled, I think I will go the cat lens route, these cheap cat's are sold under a good few brand names even though they often look identical, i need to research which are the better of the cheap brand names to see if any one name comes out best
thanks
Tazkb is offline   Reply With Quote
Old Jul 26, 2009, 7:51 AM   #8
Senior Member
 
TCav's Avatar
 
Join Date: Sep 2005
Location: Washington, DC, Metro Area, Maryland
Posts: 13,572
Default

They're all made by the same company. I beleive it's Samyang.

Since the catadioptric lenses only support manual exposure, if you going for wildlife and need to pan or recompose, your exposure settings might not work fo rth enew composition.
__________________
  • The lens is the thing.
  • 'Full Frame' is the new 'Medium Format'.
  • "One good test is worth a thousand expert opinions." - Tex Johnston, Boeing 707 test pilot.
TCav is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 4:58 PM.