[Nass]

Hello,

I'm looking at purchasing some non-mirror lenses for the 500mm+ range but the Pentax gear is just too expensive. There do seem to be some cheapo lenses on eBay that don't have the cachet of the Pentax name but if you're on a budget, I think I can live with the results. But I'm not entirely sure since I don't have one to try out Does anyone have any experience of these? There are various brands around - Samyang, Falcon, Opteka etc. I don't mind in the least that it's manual, heavy and needs a tripod!

Thanks

For reference - Opteka on Flickr

[xjjohnno]

Can you live with poor image quality? You have to pay for the length if you want passable results.

[Nass]

Can you live with poor image quality? You have to pay for the length if you want passable results.

In an ideal world, no! But my kids occasionally like to eat

[georgweb]

Hi Nass,

I'd recommend a 300mm refractive lens + T-con. You should get lens + T-Con for well under 100$:
https://www.pentaxforums.com/forums/531816-post182.html

more:
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/56246-any-expe...m-f-4-5-a.html

Don't know whether the Pentax autofocus T-Con is worth the price, but maybe it is.

A mirror lens is an alternative, but you need a good one and good PP skills (see the mirror threads in this forum section).

Best, Georg

[xjjohnno]

Great suggestion George, those Tair 300s put out decent results and probably far surpass those Samyang/Phoenix/whatever teles. I also spot quite a few for sale in the UK and EU at reasonable prices. With a little luck you might snag a non photo sniper version which seem to be a pain to use. The sniper version is built to work off a gun stock which has a focus wheel and I think some whacky aperture control.
Seriously though Nass, some of those cheaper teles are going to have you feel like you just threw good money away and be aching for something better. I can't think of the brand off the top of my head but there is a not too bad Russian mirror lens I think sold through the Zenitar website that might be also worth looking at that I've seen very decent pictures from.

[Nass]

Yeah - thanks all for the replies thusfar, it's really helpful.

[Rondec]

I was going to suggest a mirror lens -- just learn to avoid donuts.

[georgweb]

(xj)John(no) said:
The sniper version is built to work off a gun stock which has a focus wheel and I think some whacky aperture control.

I use that version on a normal tripod and find it quite nice to focus actually. The aperture is quirky but funny to use. I recommend to close the aperture to f5.6 and leave it there.

Best, Georg (the other)

[deadwolfbones]

You can pick up the Tamron Adaptall 500mm mirror for ~$250 here on the marketplace, from time to time.

[StephenMerola]

I have a rare Sigma 500mm f/7.2. I have only seen 1 for sale in my life and I bought it. I have seen some very sharp shots from others with this lens, but I have not used it enough to really comment.

[Marc Sabatella]

There are basically three kinds of long focal length lenses.

The best and most expensive kind is usually the true telephoto - one in which the optics are designed such that the actual length of the lens is less than its focal length. These are the ones one normally hear about - the DA primes and zooms, the Sigma 500mm zooms, etc.

The cheap ones you generally see under the names you list are of a different construction entirely. They are very simple optically - just one optic at either end of a long hollow tube that is as long as the focal length of the lens, like a simple refracting telescope. So they are *huge* compared to telephoto lenses, but also often much lighter. 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).

And then there are mirror lenses, which are kind of sort like the above preset lenses but using mirrors to shorten the tube, just a reflecting telescopes do. So they too are preset lenses (no aperture mechanism) that are much lighter than equivalent telephotos, if perhaps somewhat heavier than the "refracting telescope" lenses, because a mirror probably weighs more than the hollow tube it replaces. The mirrors makes them not only shorter than the "refracting telescope" lenses, but also shorter than true telephoto lenses. The mirrors also eat light (making them a bit dimmer than their advertised aperture), reduce contrast, and create funny donut-shaped bokeh at times. Still, see the Mirror Lens Club thread in this forum - even the cheap ones aren't necessarily as bad as some claim.

Anyhow, I've tested one of the cheap long preset "refracting telescope" type lenses. It was a 600-1000 zoom sold by Ritz/Wolf under their Quantaray name, so who knows who actually made it, but probably the same basic make as the ones you are seeing. I'd say it's only advantage over a mirror lens is that you don't get donut bokeh. But optical quality was no better overall - sharpness about the same, contrast a little better, but you pay for it with really bad CA. Given that price is comparable to that of a mirror lens, and it's a *lot* longer (like maybe 10 times as long!), I can't see the point of one myself. Either get a real telephoto lens if you want the best quality and don't mind the weight and cost (although certain used telephotos might be available relatively cheaply - see the other responses here), or a mirror lens if you don't mind sacrificing optical quality in order to keep cost and weight down. Again, see the Mirror Lens Club for evidence that even a $100 mirror lens (eg, the one I use, which I bought used for half that) can take some decent pictures if you learn to use it well.

[Ash]

And the Tamron 500/8 mirror is acclaimed to be one of the sharpest mirrors around.
I can vouch for that.

[Nass]

Fellas, I hear what your saying, but... well I just simply can't stand donuts in images (sorry Ash I know you love your mirrors, call it a character flaw on my part!). This limits my choices... and as I said, my kids do like to eat sometimes!.

There are 2 drop dead gorgeous Pentax 500mm sitting on shelves ready to be sold in a shop near to me. At the mere price of £999 each. Now what sort of guy would I be if I went out and bought one of them rather than pay for my little girl's riding lessons for a few months, something that she looks forward to every day

People in this forum are obviously immensely proud of their equipment and yes the Pentax stuff is fabulous, but for something that I'm only in a position to use on weekends and before/after work, and only when it's a long-distance image... well you sometimes have to make choices, even if they're sadly not the choices you would make in an ideal world

[audiobomber]

Hello,

I'm looking at purchasing some non-mirror lenses for the 500mm+ range but the Pentax gear is just too expensive.

Why not get a Pentax 55-300 and crop to a 500mm fov with all those K-7 pixels? The image will probably look better than you'll get from some old dead cheap 500mm hollow tube.

[Marc Sabatella]

Why not get a Pentax 55-300 and crop to a 500mm fov with all those K-7 pixels? The image will probably look better than you'll get from some old dead cheap 500mm hollow tube.

I'd say based on my tests with the Quantaray "cheap hollow tube" that it would probably behave *slightly* better than simply cropping, at least when doing large prints, or crops from that crop - just as my cheap mirror lens does when comapred with crops from my 50-200 on the 10MP K200D. But at typical print sizes, or just viewing the image on screen, you're right - the 55-300 undoubtedly will do as well. And the 55-300 would be a stop faster, have more DOF, support auto focus, and be a fraction the size.

Here, BTW, is the one sample I had uploaded a while back. First the (resized) full image from 600mm:



And here's a 100% crop from my 10MP K200D (14MP cameras will of course expose the flaws of the lens that much more readily):



This one is not bad, really. Other shots showed CA much worse than this one.