Funnily enough, so was I.

That'll teach me to pay attention...

It sounds very plausible.

The best converters are useful and cause little degradation, but the worst are truly awful.

After all what? The message was that pretty much all older Pentax lenses can be used with the DSLRs, but those of the Series or later are more convenient. This does seem very straightforward and you won't find such a degree of compatitbility elsewhere.

What did you choose to do in the end?


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I'd rather have several smaller cards than one large capacity one.

This is on the prinicipal that if a card should fail (and they do) then fewer images would be lost.

Being a JPEG sort of person (somewhat compressed, sometimes depressed) a 512 MB card will fit niocely onto a CD, also making back-up very simple indeed.

Is it possible that it has high resolution but slightly lower contrast?

Many lenses are designed to be quite contrasty and this gives a harsh but punchy result - quite unsuited to portraiture.

Maybe the 77mm just has a different balance of properties, a more subtle mix.

Only a portion of the coverage of a lens that is designed for 35mm cameras is used. A lens designed purely for the smaller sensor uses its entire covergae and is unsuitable for "full frame" SLRs.

It would be a lot more money and of debateable advantage. Noise should be lower in a full frame sensor as the individual photo diodes could be larger. But resolution would be the same, MP count for MP count, so as the manufacturers get better then the need for a full frame sensor should reduce.

Yes. A 50mm lens, for example, acts as though it were a 75mm lens in terms of its field of view.

A digital-only lens has an image circle that matches the size of the sensor. This makes the lenses smaller, less expensive to manufacture and also enables more ambitious designs to be attempted. 25 years ago a 12-24mm f4 zoom lens of professional quality would have been beyond belief. Now we have one, and at an accesible price.

Hope that helps, if you have more questions, please ask.

Pentax didn't design it that way, the laws of optics did.

If you could be more specific about what you need to know we'd be happy to try to provide the answer.

What is the bit of information that needs greater detail?

Digital lenses are designed to cover the area of the CCD, a smaller image circle than the 35mm frame would require. They also have a more telecentric design - that is, the light rays exiting the rear element of the lens are as parallel as possible.

The "crop factor" is a way of expressing what happens to the field of view. A 50mm lens will, for example, always be a 50mm lens, regardless of what format it is used on. However, compared to 35mm film format, only the centre of the field is used on a DSLR. This is equivalent to cropping the full frame image and the effect is as though it were a 75mm lens on 35mm format. This is the 1.5x "crop factor". If you think about this, it may have the field of view of a film camera's 75mm lens and hence be suitable for portraiture, but also it still has the depth of field on a 50mm lens.

This latter point has been argued to extinction on this and other forums, but in practical terms this means more DOF on smaller formats for a given field of view and less DOF on larger formats.

This is well borne out by the extremes, where a standard lens on Minox sub-min cameras is 15mm and has immense DOF and on say a large format camera 210mm with very little DOF.

In 35mm terms the ideal portrait lens is around 85-100mm. The perspective is good, the photographer doesn't crowd the subject and yet is close enough to communicate properly.

So in terms of digital a 50mm focal length or thereabouts works very well.

This makes even the kit 18-55mm lens perfectly useable for portraits. The 50-200mm also is fine. I've even used the 16-45mm with good success. The 50mm f1.4 also is excellent.

You don't need to worry too much which one you choose as the 1.5x crop factor brings all these lenses into the mix for consideration.

There's no real need for a macro lens for this either as you will not be getting that close. A macro will be a bit cruel on skin texture as well.

Welcome and have fun!