There are plenty of things I wonder how Jessops get away with. Recently my wife bought a lens for her Canon. We were in the Jessops store and noticed the store price for this lens was £80 (!) more than the online price - even if you just ordered online and picked up in store. When I mentioned this to the sales assistant he said "You only get that price if you order online first" to which I responded "I could do that on my mobile phone right now". He responded that yes I could and indeed people had actually done just that, in the store, to get a cheaper price. "Given that's the case", I argued, "why don't you just save us the bother and give us the lens for the cheaper price anyway?" Apparently they could not do that.

Fantastic customer service as it boils down to "Yes you can get it cheaper without even leaving the store but only if you're prepared to inconvenience yourselves for our amusement first".

We bought the lens in Jacobs, who matched the (lower) Jessops price, instead.

Well rightly or not, Pentax referred to 645 as "Medium Format" and have chosen to refer to the 645D as "Medium Format Digital". In the absence of a better name, I'm guessing that's what everybody else will choose to call it too. In fact that's what they are calling it already in photography magazines, websites, blogs, down the pub over a pint and so forth. So the point you are making is shortly destined to become - if it hasn't already - purely technical pedantry.

You could argue of course that it is a "crop sensor" in relation to a full sized medium format sensor, and indeed be technically correct - but since almost everybody understands the term "crop sensor" to mean cropped in comparison to the size of 35mm film that would be pretty misleading, and in all honesty smacks of being deliberately abstruse.

Makes me wonder if anybody has tried to mount one of these on a NEX. That would not look silly at all.

Actually I'd like to see one mounted on a Q!

The 645D's sensor is not a crop sensor, it is a "medium format" sensor. Although it still technically has a "crop factor" (albeit of less than 1 because it's larger than 35mm film) this can more correctly be referred to as a "focal length multiplier" to avoid the confusion - or alternatively for anybody who doesn't know what a focal length multiplier is, make it worse.

You have a point there. The whole "35mm" thing is probably inherently confusing to beginners since we're talking about focal lengths which are also measured in millimeters.

When thinking about focal lengths on different formats I actually find myself mentally converting to "APS-C equivalent focal length" rather than 35mm. To me, a 50mm lens is (for example) what the long end of my Tamron 17-50 gives me on my K-5.

But then, although I started with film I had nearly 20 years break before getting into digital! In a way I think that is an advantage because it means I can easily relate to the viewpoints of both those who started on film and those who started photography with digital.

I don't think it has so much to do with a profusion of older lenses so much as a profusion of different sensor sizes, which is becoming more and more of an issue as various different interchangeable lens systems with different sensor sizes enter the market. As long as all these different sensor sizes are around there needs to be some standard for describing field of view that people understand, and "35mm equivalent focal length" is that standard by default. Arguably "angle of view" would be a better standard because it does not rely on assuming any particular size of image circle (but it does have the disadvantage that the mathematics involved in calculating it are more complicated).

I wasn't trying to make the point that we should stop using that 35mm equivalent standard. Actually more or less the reverse - I was making the point that if we're using an APS-C camera, the field of view a lens would give us on 35mm is completely and utterly irrelevant. It is only the field of view we will get on the camera we're actually using that matters - regardless which terms we choose to describe it in.

As for older lenses, if full frame or four thirds digital cameras did not exist, or more to the point if APS-C was the only standard in town then no digital photographer who was raised on digital and had never used film would care what kind of field of view these old lenses gave on 35mm film at all. They would use those lenses if appropriate for the field of view they give on APS-C and not would bother even thinking about it in any other terms, because to do so would be largely pointless.

As an example if you're using a old 50mm lens which was designed for 35mm film on an APS-C camera, it's "35mm equivalent focal length" is actually going to be around 75mm. In a world where every digital photographer used APS-C this fact would simply be more confusing than useful. I can just imagine the reaction of a novice: "Wait a minute, you're saying that a lens which is 50mm on 35mm film is equivalent to 75mm on 35mm film... WTF?"

Excellent shots! Makes me want to go out again and have another go with longer lens.

BTW in case you can't think of a good use for a 70-200 F2.8 on ASP-C, it is perfect for shooting indoor sports where the extra stop actually makes a difference and the environment is not really large enough to need anything longer than 200mm (but 135mm isn't really going to quite cut it).

I personally can think of plenty of other uses too, considering the 55-300 is one of my most used lenses and I don't actually don't need the extreme long or short ends that often (with the exception of shooting wildlife, which tends to employ the 200-300 range) and using it to shoot anything that moves much faster than a jogging pace even in daylight could frankly benefit from an extra stop or so. Particularly bearing in mind the daylight here in Scotland tends to be dull and overcast much of the time.

I'll shut up now. I'm probably not in the best of mood to be participating in online debates, so if I have put anything in an unnecessarily confrontational manner I apologise.

In my opinion this argument has gone way off track and become increasingly ridiculous. Point one made by myself (and others earlier in the thread) is simply that 50 - 135 on ASP-C does not give you the same field of view as 70 - 200 on ASP-C.

Focal lengths on 35mm film really have nothing to do with it because we ain't using it, and more to the point because folks who were raised on digital and not on film do not have the same expectations about what makes a good range of focal lengths for their needs, because this is at least partly based on familiarity - simply what they are used to.

And point two is simply that 70 - 200 f/2.8 offerings from Sigma/Tamron sell, and the people who are buying them are buying FOR ASP-C CAMERAS! (you might recall Pentax don't do any other kind right now). Ricoh/Pentax can either compete in that area, or not. From earlier comments, I'm clearly not the only person in this thread who would tempted if they did. End of story.

I really don't see how there is any sensible argument against these points.

So 70-200 is not an great focal length for portraits on ASP-C. Granted. Most people buying them probably don't have portraits in mind. There are plenty of other uses for this range of focal lengths. The fact that Pentax do a 60-250 F/4 hardly makes the very idea of a 70-200 F/2.8 redundant. It is simply offering users more choice.

Personally I would rather have a 16/17-50, 28-70/75 and 70-200 combination all at F/2.8 than the 16-50, 50-135, and 60 - 250 dropping to F/4 combination that Pentax offer. It's not the F/4 that's the issue, it's the fact that the overlapping focal lengths low in the focal length range (17-50 to 28-70) will actually save me far more lens changing than overlapping focal lengths higher in the range (50-135 to 60-250). If I simply miss out the 50-135 altogether because, let's face it, 51-59mm is not a desperately large gap then it will not save me any lens changing at all. This will hold true unless I radically change my shooting style. Different people have different shooting styles, hence different needs for focal lengths. I'm sure Pentax's approach is more suited to some, perhaps even most... but clearly not all

...And obviously not me. So as it stands Tamron or Sigma are more likely to get my money than Pentax.

As for portraits, the middle lens in Sigma/Tamron's F2.8 range, the 28-70/75 may have started life as a 'standard zoom' a tad too short for portraits on film but it actually makes for a pretty good portrait range on ASP-C and a lot of people now use it for that purpose.