[wim]

Hi Ian,

[quote name='IanCD' timestamp='1321880322' post='13110']

Hi Miro, (and BC & Wim)

Actually, I have got the answers I wanted, thanks to Wim, BC and others

As I said earlier, Wim, the links you provided were just what I was looking for...



Some of the difficulties which triggered me posting this thread are related to how I view the images... they look reasonably sharp at 1200 pixels wide, but they aren't tack-sharp where I want them and I see that clearly at 1:1.[/quote]

They may not be tack sharp at 100%, for a variety of reasons. AF (just like MF really) is a bit of a lottery, also called statistical variance <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='' />.



Other than that, there also is the human factor. We humans actually keep our balnce dynamically, so unless you are shooting from a tripod and MLU, you mauy find there is variation in focus just from that - humans easily sway +/- 2.5 cm when keeping balance and from tensioninf and detensioning caused by just our heartbeat.



In order to countereffect these, you will probably be at F/4 or even F/5.6 most of the time, I would think.

And as I also said, this is partly also related to the fact that I know the autofocus on my camera has become unreliable, so I wanted a rough idea of the aperture I would need to use to ensure a given amount of leeway. I hope I won't need that when the camera comes back, but it's still useful to know, nevertheless.

That is something I can't help with from here, of course, and it can happen indeed. One question, though: I assume this happens with all of your lenses?

Now, thinking about the antagonism that gets into some of the threads here at PZ from time to time and which I guess I've found as off-putting as anyone else - I specifically asked that it be avoided this time...



And, actually, though the tone between BC and Wim could be seen that way, on reflection I don't think that's what has happened this time. And, certainly, I don't think any antagonism has been intended. You're debating points of view that you believe to be right, and the way you express that sometimes gets quite passionate and, particularly BC, quite strident and robust (e.g. the CAPITALS - perceived as shouting on most internet forums).



BC, both your simple equivalence calculation (aperture and FL equivalents can both be approximated by multiplying by the crop factor) and, Wim, your - as usual - more technical, erudite, explanations are very valuable and helpful here - as well as the input from VL, Serkan and others.



Incidentally, I'm looking forward to having a lot more time for practising photography in a few months, rather than just grabbing the occasional day every few weekends (lucky me!)... one of the things I'm planning to do is to take a weekend workshop or two in landscape and portait photography... found a photography school fairly close to where I live: [url="http://www.photography-courses.com/"]Blackthorn Photography Centre[/url]



Best wishes,



<img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/smile.gif' class='bbc_emoticon' alt='' />

Ian

Wow, looks very nice indeed. I lived in Newbury for five years, working all over the place, amongst others in Cheltenham and Oxford. Beautiful area, great for workshops, for sure.



Kind regards, Wim