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Graham , not much help, but FYI

According to 'Boz' http://www.bdimitrov.de/kmp/lenses/primes/wide-angle/index.html the 'FA' is optically different to earlier F , A and M series, which do allow access to the front element.

Looking at the schematic diagram, it does seem that it should be possible to separate the front element. It might be worth calling Johnsons http://www.johnsons-photopia.co.uk/ to discuss the proble. I have found the guys in thier technical department most helpful. Ask for an official Pentax PDF for the lens and hopefully that should help you on the way.

Regards - Steve

I purchased one of these screens a couple of months back, as described it is a OEM part without the box and tweezers. Mine took around 10 days to arrive.

Regards - Steve

Tim, my understanding is that there is benefit (up to a point) to be gained by using the longest hood possible that does not cause vignetting. The benefit I believe is more pronounced on digital than with film.
As to why 50mm lens hoods are not longer, a hood the length of the one supplied with the 50-135 would probably cause vignetting at the wider apertures usually associated with a 50mm lens. That aside there is a a law of diminishing returns and it would make such a lens quite unwieldly.

I agree with Stefan, in that the crop factor needs to be taken into account , when considering a replacement hood. So in the case of your 85mm Takumar I would be looking for something originally designed for a 135mm lens. I purchased one of the expandable types described in the article for use on a 35-105 lens and it does work pretty well.

By way of illustration many DA lenses will show less vignetting on a full frame SLR with the lens hood removed.

Regards - Steve

This article provides a pretty good explanation http://toothwalker.org/optics/lenshood.html

Regards - Steve

Matt, I use mine on manual as part of a remote slave set up . The zoom head and bounce allow provide added flexibility

Stefan is right, moving the zoom added from wide to telephoto will focus output and so provide additional range. My earlier comment related to no additional power being outputted from the head. Unlike the Af200T, which I also have there are no 1/2 , 1/4 , or 1/8 power settings, which do actually control power output from the head.

Regards - Steve

Hi Matt, I too have a AF240Z amongst my collection of flashes.

Regarding the swith marked 'zoom' as far as I am aware moving it does not change output power. As you say it moves the distance/aperture scale, so when using the flash in manual, you would ensure that the setting on the head matches the setting on the zomm swith and set the exposure manually.

'Boz' http://www.bdimitrov.de/kmp/flashes/non-TTL/index.html lists no accessories and I have never come across an adapter for wider than 35mm. The manual, such as it is makes no reference to a wide angle adapter.

The flash does have a slot for filters, so maybe a slide in adapter was available originally.

Regarding the Sepia filter, it was not uncommon in the 80's and possibly before to find flashes supplied with several coloured filters. I never used them myself. but I am sure someone on the forum can provide more detailed information on their use.

Regards - Steve

Since the lens is no use without its mount, heat up the mount with a hairdryer and then try removing the screws.

Not really, following the link, the text describes a lens that covers a full size sensor, presumably 135mm full frame.

At the wide end the two lenses would give roughly equivalent fields of view.

Steve

Firstly I must say that I have no experience of SDM drive lenses, but reading through the comments above, the insight that I get, is that SDM performance more than anything else is variable.

In a previous life I was a Polymer Chemist and I spent a lot of my time formulating rubber materials for use in aerospace. About 15 years ago we were developing an application that required a component to not only seal, but also provide a constant low friction interface between 2 surfaces. To cut a long story short, it proved to be one of the most difficult developments that I was involved in, we could not maintain a coefficient of friction within the tolerances required. Temperature at the sealing interface is key, but there is also another factor that is equally important. Rubber compounds contain materials in 'solution' some of which have a tendency to migrate to the surface with the subsequent effect on friction. In the case I describe this ultimately resulted in a total product redesign.

If the lenses in question require their sealing materials to behave in a similar way then I can envisage similar problems. A repair technician would not know, as they are not trained design engineers. Replacing the SDM and seals are easy options.

As Glyn alluded to, maybe the SDM motor is slightly underpowered and a combination of components at the extremes of their individual tolerances are be responsible for the problems. An interesting exercise would be to test the performance of one of the problematic lenses with its WR seals removed.

Coming back to the problems encountered, stickiness in the focusing mechanism is often sighted, particularly after a period of non use. I have a routine of regularly exercising (focus, zoom and aperture)all of my lenses to prevent such problems occurring. It was advice I was given almost 30 years ago, when I purchased I purchased my first camera SLR and it is something I have been doing since.

For those with recurring problems 'SDM' related problems this maybe worth considering.

Apologies for the long post -regards Steve