Upgrading from Kx to K5

Started Jan 3, 2012 | Discussions thread
Stefan Carey
Contributing MemberPosts: 807
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Re: Upgrading from Kx to K5
In reply to Gerry Winterbourne, Jan 6, 2012

Dear Gerry, thanks for taking the time to so elegantly and clearly explain this to me.

Much obliged.

I especially liked your point about printing, which for me helps put a lot of discussion about resolution into perspective. So it seems a KX, KR or K7 would suit my needs quite well.

cheers

Stefan

Gerry Winterbourne wrote:

Stefan Carey wrote:

If the difference in quality of a lens used on a Kx and on a K5 is so apparent, how does one work out which lens will not give good results? Is there a measure one can use? Resolution? Is it really that obvious?

I don't think the difference between K-x and K-5 will usually be very obvious. If we think in purely resolution terms the measured resolution (on Photozone) for high-IQ lenses goes up by about 20% while the linear pixel density goes up by 26%, when comparing K-5 to K10. Going from K10 (10MP) to K-5 (16MP) via K-x (12.4MP) and K20/K-7 (14.5MP) the increments are about equal. I honestly don't see a difference between my K-7 and K-5 except for really fine detail; there must be a difference from K-x to K-5 but it won't usually matter.

I worry that if I were to buy a K5 (a possibility I keep trying talk myself out of to simplify life), then would these three lenses (my favourites) be less than 'great'?: Vivitar 105mm 2.5 macro, Pentax M 50mm 1.7, Pentax 16-45mm. Has anyone tried these on a K5 and were they happy with the results?

It depends on how you think about it: at 100% any deficiency in a lens will be more obvious with a higher pixel count. However, at equal print size the difference should be invisible.

Think of it this way: imagine some sort of "perfect" resolution - as soon as you put a lens into the equation that perfection is eroded; as soon as you put a sensor into the equation perfection is eroded again. So what you see is "perfect" minus lens effect minus sensor effect.

For the same lens the lens effect stays the same; for a better sensor the sensor effect gets less. As these effects are reducing resolution, you'll get less reduction with K-5 than with K-x. What this means is that you should actually see slightly better results from K-5 than from K-x.

Every lens has its limits: the better the lens the higher the limits are. If the sensor gets better than those limits the improvement stops, but even then there is some improvement. I'd be very surprised if the lenses you list are at thir limits on the K-x.

I think the real questions come the other way: if you ignore all the benefits of controls etc and your only concern is IQ, then poorer lenses have no room to improve so the cost of a K-5 is wasted. But I doubt if you are near that posirion.

Good luck to all for the new year

And to you ...

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Gerry

First camera 1953, first Pentax 1983, first DSLR 2006
http://www.pbase.com/gerrywinterbourne

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The image is more important than the equipment.

http://www.stefancarey.zenfolio.com

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