2xConverter

I have Pentax 80-320 & 100-300 AF lenses i know that if i use a converter i will loose 2 stops. Also i could loose quality at the high end using AF, but would i get a better result when working in manual mode. If so any recommendations on type/make

To be honest, I would avoid tele-converters like the plague, but that's my personal opinion. No doubt some would dis-agree. However, if you insist, try

http://www.sigma-imaging-uk.com/accessories/tele-converter.htm

The Pentax 1.7x AF Converter is a good option. I've used it with the Pentax SMC-FA 80-320 with good results. You do lose some contrast as well as a couple of f-stops, but nothing that can't be rectified in Photoshop with the *ist-D

It also has the unique advantage of having internal focus - so the AF adapter does the focus and not the lens! This means that telephoto lenses focus quicker because there's no weight to move. In addition you can use manual lenses and have focussing.

Worth checking out if you can find one
Matt

My experience is that the 4 element 2x TC's are poor but the 7 element ones are pretty good. I've got one of the Kenro ones and I've found it to be a good performer however it does introduce a bit of CA.

All the Pentax t/cs are excellent, but of course it pays to use a good lens to start with.

G

Hiya,

Converters are very much a big compromise. Even the very best ones degrade image quality quite a lot, if you just use small prints you may never see any difference, however if you enlarge much at all or use a tripod, you certainly should see the difference.
I personally am with the first respndant above and would not go near any converter unless you just use 6x4 inch prints.

Also, to suggest that photoshop, or for that matter any software can correct the problems of a converter is simply not being realistic, you cannot just 'replace' the image information lost just by a few mouse clicks. This 'sort it out' after attitude with digital users is frankly not sensible...any additional 'adjustments' in photoshop degrades the image file and you cannot correct for the inadequate optics used.

cheers Steve.

Steve,

Have you ever used a Pentax tc on a good Pentax lens?

G

I use a very cheap 2x converter for some of my motorsport shots - Teleplus 2x converter, £15 on Ebay

It's used between and Ist D and a 70-200 f2.8 EX DG APO - so losing two stops isn't really an issue for me, the autofocus is fast enough for motorsport and any reduction in image quality is pretty minimal (i shoot JPEG not RAW)

Obviously if i use that lens without the 2x (and for that matter without the UV filter on the front) then the quality is even better, but i was suitably impresed with the results.

Hi G,

I have to say no..but I did try a Zeiss one on a Contax Zeiss lens and was underwhelmed and I cannot imagine a Pentax one being better...

cheers Steve.

Well I have to agree with Steve

I have all the Pentax TC's (apart from the two "A-L" versions) and I find results less than inspiring on large prints, even using my "good" lenses like the M*300/4 or K135/2.5.

On digital I don't bother with them at all and just crop and upsize on the computer.

Just my 2p worth
Reuben0

Are you saying that a UV filter degrades the quality???

It all depends on the quality of the filter. Multicoating is important, since the filter becomes the front element of your lens system.

So don't skimp on a cheap filter. Get a B+H or Hoya multicoated filter.

ANY piece of glass will degrade the image quality - the more you have the worse the quality becomes. That's just a matter of Physics.

Even the best filter in the world will still degrade the quality of the light coming through more than no filter at all. It's all a matter of trading that off against the benefits of the filter - I shoot motorsport - so my rather large gravel catching front element will always stay protected by a UV filter

All filters affect the light passing through them (they wouldn't be called filters else). In most cases they affect the light in such a way that enhances (we think) the captured image. In some cases they affect the light in some miniscule and probably imperceivable way, but affect it, they do.

I tend to use UV filters on my lenses rather than skylight etc. for protection only and if I come across a particularly striking composition . . . I remove the filter, take the shot(s), then put the filter back. Why? I prefer to use these filters only for protecting the front element of the lens when wandering around woods, crowds etc. because I think the lens manufacturers have enough coatings on their products that are far superior to most, if not all, available filters, even multi-coated ones. So where is the sense in covering several hundred pounds worth of state of the art optics with a £5 filter ?

Many pro's, even those who crawl around jungles and through rivers with their gear, don't use protective filters, only perhaps polarizers and ND grads etc. for effect, not protection.

Cheers,

Totally agree.

The more expensive the lens, the more reason to avoid a filter because then you are compromising the superior optical quality you have paid so much for.

Protective filters are only good for protecting lenses that aren't worth protecting.

Of course, if you are subjecting the lens to unusual and unpleasant conditions, then a protective filter may make sense. But in normal circumstances, if you value the lens, don't spoil it with a filter.

G