Where can I get a 800mm fixed telephoto lens?

I have a 400mm lens which I have used a 2x adapter with. But the loss of quality is unacceptable, my images are just not very sharp and they have poor contrast and I obviously loose quite a bit of light. So I would like something around around the 800mm, but pentax don't make one and sigma have just discontinued theirs, and only do a Zoom lens at that magnification. I have a pentax *ist D body

What lens should I buy : :

Sam

Before you buy a new lens, I wonder what sort of 800mm lens you have?

In general, with such a long lens, there will be problems with sharpness because of camera shake. You would need a very solid tripod and high shutter speeds.

At long distances aerial haze will reduce sharpness and contrast, so a UV filter may help, but it must be of the very highest quality to avoid image degradation.

Using the *istD with a 800mm would result in a 1200mm-equivalent, and this is very long lens territory indeed. I don't know how much experience you have had with such lenses, but I would expect a fairly long learning curve to get the best out of them.

I suspect that cropping would be a reasonable option.

No light loss

With 6MP to play with you can crop to 2272 x 1704 and still get an A4 print out of it.

Less need to set your tripod in concrete, no change to contrast. flexibility in composition - plent of plus points.

If you really need a long lens, there used to be a bunch of Russian (manual focus) lenses that were avaialble in PK mount - try SRS Microsystems in Watford (01923 226602) or Mr CAD in Croydon (020 8684 8282) who may know if they are still aroind.

John:
just to conferm that I was using a 400mm f5.6 smc lens, with what is a cheap 2x lens, maybe a better quality converter could solve a lot of my problems.

Terry:
cropping does sound reasonable, but the online stock website that I use most of the time, requires images greater than 3000 pixals on the longest side, which is rather limiting.

Thank you for your advice this is not a decsion I am going to make quickly

Hi,
When Pentax sold the 1000mm lens, it came with a special tripod which was very substantially built because of the reaons of lens shake already mentioned. These do sometimes come up but are not cheap. The other problem with such long lenses is haze. You are probably trying to get good detail at a far distance and you will need a very clear day to achieve it.

If you go away fom 800, there were some 1000 mirrors around at reasonable cost.

Kim

For all you long sighted folk there's a Pentax 1000mm f/8 Tele-Takumar Lens on eBay.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=4688&item=7521383425&rd=1

Just noticed this one too:
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=4688&item=75186...

I would be very carfull about the one I posted first, user has no feedback and is using the same photos as this one.

Why not just crop and then upsample to 3000 pixels? They'll never notice

Seriously, though, I'd concur with the above comments about stability and haze. If the sun's out you'll find heat haze can be really limiting at high focal lengths.

I'm in the same position myself. I've got a 400/5.6, albeit a sigma, a 300/4.5 and a 500/f8 mirror, and none of them ever seem long enough.

You could get an 800mm lens, but it'll put a massive hole in your wallet (about the size of a small car). Perhaps you should look into getting a better 2x convertor? They do vary a lot in quality, and a good convertor will show up any failings in your lens. My sigma 400/5.6 is a nice enough lens, but a 2x on the back really brings out the chromatic aberration.

Another way to go is to get something like a 300 f2.8, which would give a usable (but not exactly fast) 800mm by stacking 2x and 1.4x convertors, and be very handy au naturelle. This is probably the way I'll go, but I'll still need to save up a bit.

You can get Russian 1000mm Mirror lenses for around £100-200. Try searching for "Maksutov" on ebay. I've not used one myself, and I doubt the optical quality will be up to much, but it might be a cheap way to find out if you really want such a long lens.

Also, Pentax apparently now make a PF-CA35 adapter which will convert the PF spotting scopes into ultra telephotos. PF-65 becomes 780mm f12, and PF-100 a whopping 1250mm f12.5. It only seems to be listed on the Japanese site, though: does anyone know if it's available over here?

http://www.pentax.co.jp/english/products/sougan/scope/pf-ca35/spec.html

Even if you don't have a scope already, it might be a viable option. If anyone's used one, I'd be really interested to hear from them.

Finally, the cheapest (though not necessarily the easiest) option is simply to get yourself closer to the action.

Let me know how you get on,

Steve

http://www.siblingmedia.com/
http://www.siblog.co.uk/

A relatively cheap but decent quality option might be the Tamron SP 500 mirror lens and SP 2x Flat-Field Tele converter, not forgetting that you'll need a Pentax KA adaptall mount to go with it!
You could probably pick up all three for around £100 on eBay

was going to call Sigma and ask them about why they changed what lenses they make they now do a 300-800mm zoom, but have been busy, I think If i want the increase in quality I will have to spend the money.

Thankyou for all the advice

Sam

Spoke to sigma today, and although they didn't tell me why they had only just released 300-800, they did tell me that they are going to release a 800 fixed telephoto in the future they guy I spoke to wasn't able to give me a time frame.

Sam