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09-04-2009, 03:07 PM   #16
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Orion 120ST 600mm F5


YouTube - Pentax K-7 test Orion 120ST (600mm F5) refractor in 1536x1024 *** mode

09-04-2009, 05:17 PM   #17
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Tair 300, it looks like a great lens and I've taken some test pictures will post them shortly.


By mudplugga, shot with Canon PowerShot G3 at 2009-09-04


By mudplugga, shot with Canon PowerShot G3 at 2009-09-04
09-04-2009, 05:26 PM   #18
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QuoteOriginally posted by Marc Sabatella Quote
This one is not bad, really. Other shots showed CA much worse than this one.
It's not the CA that's bothering me, it's the blurriness.
09-04-2009, 07:44 PM   #19
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QuoteOriginally posted by audiobomber Quote
It's not the CA that's bothering me, it's the blurriness.
Well, like I said, this shot is not bad for CA. In higher contrast situations, it's even worse than the Tamron 70-300.

As for the blurriness, sure, it's not the sharpest lens on the block at 600mm viewed at 100%, but for about $100 and weighing very little, one cannot expect *too* much.

Anyhow, think how much cropping you'd need from a 300mm lens to get that FOV. I kind of doubt the 55-300 would do better if you blew up a crop from it to that size. Conversely, if you downsized the crop from this lens to the same dimensions as the equivalent crop from the 55-300, I suspect this lens might win. Meaning that for a sufficiently large print or heavy crop, you'd get better results form the Quantaray. But it's probably true that for smaller prints or screen viewing of the full image from the Quantaray, the crop from the 55-300 would do just as well.

Unfortunately, I don't have either lens to do a direct comparison. But like I said, my impression is that the situation seems very comparable to the results I get in direct comparisons on my 10MP camera between my 500mm mirror and crops from my 50-200mm: the mirror is obviously not very sharp at 100% (whereas my copy of the 50-200 is much more so), but if I print big enough or do a heavy enough crop, the mirror does win.

On the other hand, it does take more cropping to get a 200mm lens to the same FOV as 500mm than it does to get a 300mm lens to the same FOV as a 600mm, and the K-7 has more resolution to spare for this, so I could easily believe the 55-300 *might* still win this comparison. Without actually seeing the images, it's really impossible to say.

09-08-2009, 01:31 AM   #20
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Just wanted to say thankyou to all the responses, they've been very helpful.
09-08-2009, 08:37 AM   #21
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Just my completely uninformed pennyworth!

Has any one gone down the route of spotting scope+adapter?

They seem to pop up on ebay from time to time - I've never used one but could be an alternative?


Cheerz MZ
09-09-2009, 09:37 AM   #22
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QuoteOriginally posted by xjjohnno Quote
Can you live with poor image quality? You have to pay for the length if you want passable results.
I see these kind of immediate responses whenever a question about these lenses comes up. Just being cheap doesn't necessarily mean it will have poor IQ that can't have passable results. The Flicr blog that the OP linked to was pretty positive and he was very satisfied with his $89 purchase. I see these lenses automaticly dismissed but never with any posted photos. 20 or more years ago lenses of this type were sold as Spiratone 400's and Tele-Astranars and got pretty good reviews back it the day with the reviewers knowing that they were only going to be useful in certain conditions (outside, good light). These oldies can sell for more now on Ebay than they did new. I bid on a couple and quit at $70 and was surprised that they always seemed to end up selling for well over $100. Not worth it to me as a brand new Opteka isn't much more.

Maybe a better question if someone has some experience using the lenses mentioned, do these current "cheapo" teles compare with some of the old vintage Spiratones, Vivitars, etc. of similar design which now seem to be sought after lenses?

Marc, thanks for posting your shots. It seems the only people that don't slam these lenses are those who own one.
09-09-2009, 10:31 AM   #23
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QuoteOriginally posted by reeftool Quote
I see these kind of immediate responses whenever a question about these lenses comes up. Just being cheap doesn't necessarily mean it will have poor IQ that can't have passable results.
I think high resolution digital cameras and the pixel peeping we're accustomed to performing now have made it much harder for people to put lenses like this into any sort of proper perspective. Sure, viewing a picture from a "refracting telescope" type lens or a typical mirror lens at 100% will show it isn't nearly as good as we're accustomed to from shorter conventional lenses, or even longer conventional lenses if we're lucky enough to be able to afford them and strong enough to carry them. Still, for a basic full screen view or 4x6 print, quality can be more than adequate. Depends on how demanding you plan to be.

For me, wildlife photography is nothing more than a very casual pursuit - "ooh, what a pretty bird, I think I'll take a picture so I can look at it again". And for that, performing a little better than a crop from a shorter lens is really all I need. On the other hand, it's also for that reason that I ended up deciding on a mirror lens instead - same "passable for my purposes" quality, but a much smaller size more suited to someone who really can't see himself carrying around a lens as long as my arm in hopes of getting bird photos. If I were that serious I'd probably suck it up and get a 400/5.6 true telephoto (which would be smaller but much heavier and rather more expensive, if not completely unreasonably so). But even though I prefer mirror lenses overall, the "refracting telescope" style has advantages over a mirror that might be important to some - better bokeh, better contrast, brighter for the stated aperture (allowing somewhat faster shutter speeds for a given ISO).

The lens I chose may be unacceptable for others with different requirements, but just as surely, the lens someone else chooses might be unacceptable to me with my requirements. Which is why I think important for any review to try to be objective about the actual tradeoffs involved, rather than simply jumping to the conclusion that happens to make the most sense to the reviewer.

QuoteQuote:
Marc, thanks for posting your shots.
You're welcome. Wish I had some others to show, but that's all I kept from the 15 minutes I played with the lens in the store parking lot.

BTW, a couple of things I should have been explicit about when posting that image.

First, it was taken handheld, albeit lying down with my arms propped on the ground if I recall correctly. Shutter speed was 1/750, so I figure I got a reasonable chance of decent sharpness, but no doubt the lens would be capable of a little better.

Second, DOF is incredibly shallow at that focal length and that focus distance, so if you were looking at anything more than the one leaf that was in focus and trying to judge sharpness that way, you were looking in the wrong spot. In the 100% crop, it's the leaf just the left of and slightly below center. That's really not bad for a 100% crop from a 600mm that barely costs $100. The more prominent leaves to the right are an inch or two closer closer and are are outside the focus zone (they are also starting to evidence of the CA that was more glaringly obvious in higher contrast situations). On the other hand, in the resized full images, even the slightly OOF leaves appear to rendered well enough for my limited purposes.

09-10-2009, 02:41 PM   #24
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In reply to Reeftool and Marc, I agree!

Also....

I have a Tamron 70-300mm LD Di etc. and an old Vivitar K mount 70-300mm (Not the same as the big long "Tubes" I know)

And to be honest the Tamron is better in many ways. Firstly it's contrast is much better (possibly due to more advanced modern coatings) secondly its better to focus with (and I'm someone who's first AF lens was the kit with my K100D 2 years ago so didn't consider it as important when buying the vivitar) - focus is difficult with the limited depth of field and no optical focus aids - thirdly it's much lighter.

However the Vivitar is a "Classic" that I'll probably never use again now I have the Tamron

I know there are much better lenses and I also know there are much better cameras but I take photos because I love too and all of my kit suits that purpose.

I don't think pursuit of ultimate quality is a bad thing either and if I could afford to I'd love the best kit.

But for now I'm happy to wrangle the best out of what I can afford!
(Plus I can always blame my cheapo kit when I get a decent shot!!

Cheerz MZ
09-10-2009, 02:53 PM   #25
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With the big old tube I got for 26, I'm amazed that even at asa1000, handheld, I can see single individual hairs in this piccie of my daughter! That's fairly spectacular value for money in my book



Btw, Marc has it spot on. DoF & focus are insanely difficult.
09-10-2009, 03:42 PM   #26
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Another first! The guy in the sky, this time with noiseninja and unsharp mask. A very very quick and dirty one, I'm pretty sure it can be improved on it's late in the Uk and I really do need some sleep

09-10-2009, 07:14 PM   #27
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consider the Sigma 170-500mm, it is reasonably good... i guess some went for around $400-500 in the market place.. and i got mine for around $225.... on a recent trip to dallas... it has AF and that for me is quite important especially considering that it is hard to focus far and moving subjects...

here is a picture i took today evening at 500mm...
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09-11-2009, 04:05 AM   #28
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Nass,

The moon shot is incredible for a big old Tube. Truly inspiring!

I have one tucked away somewhere - a 500mm long tube with a bit of glass at each end. Time to dig out and dust off I think. Got a mirror of the same focal length too that will also need an outing.

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09-11-2009, 07:37 AM   #29
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Hmmm, I should imagine the mirror will massively show up the tube because bokeh (the only thing I truly loathe about mirrors) doesn't come into the picture. If it clears up over the weekend I'll give this another shot I think, and see what happens when I use this deconvolution freebie on it
09-11-2009, 08:19 AM   #30
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QuoteOriginally posted by Marc Sabatella Quote
...

These are generally "preset" lenses, meaning they have no aperture mechanism, but instead have a fixed f-stop (usually f/8 for the 500mm, going down as the lens gets longer).

...
Hate to be pedantic Marc (but I can't help it )... Preset generally refers to an aperture mechanism which is not coupled to the camera, but is adjustable on the lens - you pre-set the aperture before shooting the picture. The common mechanism for making this happen (from the reading I've done, and the one preset lens I have (this one)) is a double set of aperture rings, one of which sets the stops, and the other manually actuates the diaphragm until it stops at the pre-set stop. In use, you would chose the aperture you want, open the lens up wide with the actuation ring, focus, then close the aperture back down to meter (if you're camera has that capability) and shoot.

See also the "Aperture control" heading in this wikipedia article.
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