Pentax-A 400mm F5.6 vs Tamron SP 500mm F8 Mirror

Hi, I've recently borrowed a Tamron SP 500mm F8 mirror lens from a friend - to assess if its the type of telephoto I'm looking for - but I'll be honest I'm struggling to get many good shots, due to the very narrow depth of field.

In peoples opinion, would the sharpness of the Pentax-A 400mm F5.6 be significantly better than the Tamron SP 500mm ?. If so, it will give me the ability to use smaller aperture (and I don't mind sacrificing the extra 100mm and cropping more photo's if it means more in-focus shots).

Also - any history of poor copy A400 F5.6 lenses ?(They do seem to come up fairly often on e-bay - but I must admit that I'm a bit nervous of buying such an expensive lens from e-bay, without knowing the full history.....)

I would expect so. I have a A400 F5.6, and it's quite a bit better than my Sigma mirror lens, especially stopped down a bit.

It's also quite a lot better than a (non APO) Sigma A400 F5.6 that I also have, if that helps any.

It's big and heavy though.

A thing of beauty, certainly, but if you're after something lightweight that you can hand-hold all day, you might consider a workout programme first.

Or you could consider a M200 F4 and 2x teleconverter. Come to think of it, thats what I'm selling at the moment

Here are some tests I did on my M400mm f5.6

link

Greg

Often poor results with the 500mm mirror come from people using it like a nifty fifty. It may be a featherweight but it is still a 500mm lens and requires careful support, focusing and so forth. Also, using some sort of magnifier to check the focusing can help.

I dare say the 400mm is a lovely lens, but you'll still need sound technique to get the most from it.

Sorry if I am teaching grandma to suck eggs here.

K.

EDIT: some useful tips here.

I totally appreciate what you are saying about needing sound technique - as I've been asking myself that exact question - is it me? or is it the lens?

So today I have been taking a few shots of static subjects, using a tripod and flash to try and remove any possibility of it being subject movement or camera shake.

I'm now coming to the conclusion that as a fixed F8 lens at 500mm - the depth of field is increadibly shallow - much less than I expected.

But I do accept that my focus accuracy does need to improve - as again, being an F8 lens - the focus confirmation indicator in the viewfinder does not always seem to be able to lock-on - so I'm relying on my eyesight to focus.

But, as the Tamron lens is just on loan, I am in the market for a long-telephoto - and although the mirror lens is compact and light - I'm tending towards a "normal" telephoto design instead.

At 10m the depth of field with a 500mm lens at f/8 is 12cm. Even at 30m it is only 113cm. With a 400mm lens it increases to 19cm and 178cm respectively.

The advantage of the 400mm, of course, is that you can open it up wider to focus and shut it down further for more depth of field.

Best wishes, K.

I have the Tamron 500mm lens and it is supposed to be better than the Sigma mirror. But you are right, it is difficult and never really can compete with my DAL 55-300mm over similar distances. In good light and with great care, some help from Photoshop it can produce some good results. I have found with the matched 2x teleconverter you don't lose that much so you can get 1000mm=1500mm 35mm for less than £150 with hardly any weight! It's not great but acceptable and fun!

at 500mm:-


Jay in garden by dcweather, on Flickr
Dave

The Tamron SP 500mm F8 mirror lens is SHARPER with the official
UV filter it was part of the design. link

I have the Tamron and it is superb when used correctly. If you are stuggling with it I'm afraid you'll struggle with any 500 if not used correctly.

There is a load of advice on here about using long lenses especially the Tamron 500.

Algi, I've never heard of this 'front' filter, mine uses 30.5 filters behind the rear element and although I have the set of NDs, the UV has never ben off.

Thanks for all the advice.

I didn't know the importance of the rear filter - so first thing I did this eveneng was check that there is one fitted (which thankfully there is).

But, now that I've seen examples like the picture above of the "Jay in Garden" I know that this SP500 lens is perfectly capable of getting much sharper images than I've achieved so far - so I'll be searching out all the mentioned entries on how to get the best from long lenses.

I've been using Pentax gear for years - so I can't believe I've only just joined this forum (But this is my first venture beyond a 200mm lens - hence why the focus accuracy and shallow depth of field have caught me out).

I should add that the Jay picture above was taken without the rear uv filter. No particular reason, I just thought why add more glass but I haven't done with and without comparisons so maybe on what has been said above I will put it back!
Dave

......... sorry, I've just checked the lens and it might have been on!
Dave

MTF increases don't always translate into sharper pictures, especially on Digital which has it's own resolution limit. It might do on film, but I expect it would be un-noticeable on a lens that isn't a top performer anyway. The filters seem very rare and would probably be expensive being 82mm multi-coated so the best thing is just forget about it. There's probably a dealer somewhere that still has these in stock