I was responding to your contention that I had implied some apertures
can never be used under any circumstances. I pointed out that my
discussion is limited to the effects of diffraction on aperture
selection and now you're telling me that's "nonsensical"?
You'll have to educate me on your use of the term 'usable' then. I had (perhaps naively) interpreted your argument as being that high pixel pitch restricts the range of f-stops that are 'usable', and that 'usable' means 'of use', with the deduction that not 'usable' means 'of no use'.
The phrase 'encouraged to print at a given size by the pixel density'
was a direct quote from you.
Please provide us with the date and time stamp where I wrote that.
"the vast majority of people working with high-density sensors are completely unaware of the fact that they are suffering a compromise in print resolution when they choose to make prints as large as the pixel count enccourages" Davis, M. DPReview, 17/08/08.
http://forums.dpreview.com/forums/read.asp?forum=1018&message=28982514
OK, I reported from memory (it took long enough to dig it out from the volume of your posts here), but i don't think the paraphrase was inaccurate.
And actually, the whole basis of your argument, and one of
the false axioms, is that pixel density of necessity determines the
scale at which you print,
I've never said that, either. Maybe you actually are in a different
thread and don't know it. You need to support your claims of what I
did or didn't say by giving us references.
I did. Usually it is not necessary to cite references to remind people of what they said or what is the basis of their argument.
I chose 5 lp/mm arbitrarily as an example of how to use the formula
I've provided.
Well, if the figure is arbitrary, then the formula is meaningless.
Simply taking the reciprocal of pixel density does not account for
losses induced by the Bayer algorithm and anti-aliasing filter common
to CMOS sensors.
Now, as I remember this convoluted argument (and my memory's not so good as I get older) you repudiated that you'd made any link between print size and pixel density. I was merely pointing out that that is exactly what you've done, even if you are not aware of it. Not only have you done it, you've done it repeatedly.
Where did I write that one should always print at 360 dpi? Go find
it. Happy hunting...
360 dpi was simply the required image resolution to match a desired
print resolution of 5 lp/mm. The formula I provided does not mandate
ANY desired print resolution. I used 5 lp/mm and the corresponding
360 dpi as an example, not a mandate.
But if your formula is to support your contention that diffraction limits the range of 'usable' f-stops, then you must be making assumptions about magnification and 'usable' print resolution. I'd assumed as much. now you say you're not, in which case your formula is an arbitrary and not very useful mathematical relationship. If you look down to the quote of yours I've used to support another point, you'll find that the 'arbitrary', 'for example' figure comes up quite frequently in your posts.
optimum aperture and print larger.
Nothing in the above statement refutes anything I've said.
Yes, it refutes your definition of 'usable' or 'useful' or whatever was the precise word you used.
I'm only talking about diffraction here. You're absolutely welcome
to use any stop on your lens if you don't give a hoot about
diffraction inhibiting a desired print resolution.
I think you must approach photography in a rather different way from me. Generally, I don't look at a scene, think how large I'm going to print it, work out my desired print resolution and get the calculator out. Don't you find that the subject's p|ssed off by then, even if it's a landscape? Maybe I need to go into action photography, just as soon as I get myself a laser speed gun, so I can use the calculator to work out which shutter speed to set. What I tend to do, in my troglodyte way, is learn from my past practice the type of settings that I need in particular situations, to get a variety of effects that I've found successful in the past. Oh well, we live and learn.
Why, because I actually take some photographs now and then?
No, because the above statement is off-topic. I'm talking about the
impact of diffraction. I'm not writing a dissertation on all the
factors one should take into account when shooting landscapes or any
other subject matter.
And you're not talking about diffraction because you think it's one of the factors one should take into account? Sorry, my foolishness for assuming that the point of your post was to aid the practice of photography.
I never gave the advice you claim I gave. Find it. Quote it. It
doesn't exist.
"Less than about 110 pixels/mm: You can typically use all but the smallest f-Number available on the lens without compromising your desired print resolution at the anticipated enlargement factor.
Up to about 200 pixels/mm: You can use better than half of the f-Numbers made available (same qualifications as above).
Greater than 400 pixels/mm: You'll be stuck with using the widest one or two apetures (smallest f-Numbers) offered on the lens (same qualifications as above).
At greater than 600 pixels/mm: It's highly unlikely that any f-Number offered on the lens can be used without compromising the desired print resolution of 5 lp/mm at the antipciated enlargement factor had when the print is scaled to the equivalent image resolution of 360 dpi." Davis, M. DPReview, 17/08/08.
http://http://forums.dpreview.com/forums/read.asp?forum=1018&message=28992239
That wasn't advice? It was just a neutral statement of fact? Again, my apologies for assuming that you were trying to contribute some useful knowledge to this thread.
--
Bob
