Just to add slightly to that, it's important to know what a lens has been designed for, and this avoids disappointment should our requirements be different.

The SMC Pentax-M 50mm f2 and 50mm f1.7 lenses are essentially the same and are exceptionally good. The 50mm f1.4 design appears to be designed for maximum contrast at the expense of fine resolution, and thus is probably intended for low light use and reportage, perhaps unsurprisingly....This is not to my taste, but might be just what someone else requires. The 50mm f1.2 has excellent control of point light sources (great for night shots) but its best performance comes in arounf f5.6-f8, which is where it may well be used most of the time for general purposes. Looks like another deliberate design choice.

Don't forget the SMC Pentax-M 40mm f2.8, which is also excellent!

The only difference between the Pentax-M and Pentax-A lenses is that the A lenses have an 'A' setting on the aperture ring. This enables them to be used in program and shutter priority modes with A series and later camera bodies. The depth of field tables will be the same.

If you use an A series lens on a K or M camera body, the 'A' setting on the lens cannot be used.

First, you trade it in for a Pentax *istD.....

Ironically, autofocus will be happiest when there is enough light and we could happily focus manually anyway!

I only use autofocus in portrait sessions where it is fantastic to focus swiftly on the eyes, quickly recompose and shoot. Much more reliable than manual focusing.

For everything else, I use manual focus.

Hi Malcolm,

I've not tried the 18-35 but even at its low price it should not be sharp at one side and not the other. It could be that an element is displaced or perhaps the CCD in the camera body is not aligned properly - either way a replacement lens will give you the answers.

There are two high quality Pentax lenses you could try: the 20mm f2.8 or the 20-35mm f4 zoom. I've noticed the zoom being advertised by a dealer in AP at around £320 which is a fantastic price. If you are happy with a more telephoto effect then the 24-90mm is also an excellent lens, crisper than the 18-35 according to Pentax User magazine.

Do let us know how the replacement lens works out.

Best wishes

There will be an enormous difference - the 18-35 is intended as a standard lens for the digital sensor, giving an effect similar to a 28-80 on a standard film SLR.

The 17-28 allows all the straight lines to bend outwards at the 17mm end (barrel distortion) to give a fisheye effect. This effect comes more under control as you zoom towards 28mm. Now on a CCD, which is smaller the lens will give an angle of view more like a 28-80 again, but presumably with masses of distortion at the wide end. I can't begin to guess whether this will be a desireable effect or not - if you can find a dealer with a lens I would try it on the *istD and check out the effect before buying.

Looking at it the other way round - what effect are you trying to achieve with your new lens purchase? If you can define that then the way to go might suggest itself better.

Best wishes,

This lens is the fisheye zoom, which goes from a wild and wacky fisheye effect at the short ens to a fairly normal 28mm. Should be interesting...

All modern Pentax autofocus lenses should be OK with your new camera.

I have always found that the quality of lenses is really thrown into sharp focus (!) in the black and white darkroom - maybe because we make bigger prints there, even focusing on the grain of the film and so showing up any defects.

Up until very recently I have only used prime lenses for b/w work, only within the last couple of months adding the SMC Pentax 24-90mm zoom. I have to say, despite its fine qualities the jury is still out even on this zoom lens at its huge price, partly because it vignettes quite noticeably. There is no doubting its usefullness for my "Images of England" shoots, but as for exhibition prints we will have to see!

The best lenses I have owned or own for my Pentax cameras have been the SMC Pentax 24mm f2.8, SMC Pentax-M 50mm f1.7, SMC Pentax-M 100mm f2.8, SMC Pentax-M Macro 100mm f4. The SMC Pentax-A 35-70mm f4 is also remarkably good, although at close distances it needs stopping well down.

As far as I know, the 50mm lenses retain the same optical layout that has been running since the M series. If this is so, the f1.7 version is a cracking lens, clean and sharp and delivering its best at around f5.6. The f1.4 version is faster if you need it, but has higher contrast at the expense of fine detail resolution. I didn't like the f1.4 as much but I wanted high resolution for landscape work, not high contrast for low light reportage.

The 43mm f1.9 is a new breed of high quality optics that also include the 31mm and 77mm lenses. These lenses are intended to be of the very highest grade, and the 43mm is reported to have better characteristics that the Carl Zeiss 50mm which was previously considered by many to be the best standard lens of any make. At a price!

I would suggest that if your output is to colour print then all these lenses will be equally fine. If you print large monochrome picytures then the 43mm or the 50mm f1.7. If you do a lot of low light work, then the 50mm f1,4.

The price may well also be relevant, but only you can decide...

Kodachrome used to be my favourite, but the quality of processing has got worse and worse - I'm not so sure Kodak are the slightest bit interested in Kodachrome. It's increasingly common for Kodachrome slides to have a dreadful magenta cast.

Fuji Velvia has bite and intense colour - it can look pretty fantastic in our dull, colourless winter, and at the moment we are trying out Velvia 100. I guess trying out a variety of films is the only answer - find the one you like!

For an excellent processing lab we like using Transpacolor: www.transpacolor.com