Pool on Snelsmore Common

David M

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James says "...the format makes no difference..." and he seems to know what he's talking about. May I add that it makes no difference on the negative? The degree of magnification needed to make a print must be a factor in how we perceive sharpness. Ian's pictures show how the effect of wind can be much greater than any optical blurring of edges.

Martin, you put your finger on it with your comment about friendly suggestions and ideas. We all learn, even as bystanders.

If I might add a follow-up question on the printing, increasing the contrast would push the sunlit tips of the branches over the top and into blank white. Increasing exposure to correct this would make the print rathe darker. They are too tiny for burning. Would a darker print be better, and is this a candidate for print flashing?
(This is assuming a darkroom print. Digital procedure would be different – a tiny curvy tweak?)

I'm asking because I'm curious. Visualising other interpretations seems like a good way to learn.
Although, as I've said, I'd crop the image a bit (bit off the bottom, corresponding bit off the RH edge), I rather like the present tonality, but I can't insist on it. In these matters, everyone can be right.

My apologies to James if we are embarrassing him with this discussion on his first posting.
 

James T

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James says "...the format makes no difference..." and he seems to know what he's talking about. May I add that it makes no difference on the negative? The degree of magnification needed to make a print must be a factor in how we perceive sharpness. Ian's pictures show how the effect of wind can be much greater than any optical blurring of edges.
Properly what I should have said is focal length make no difference, i.e. if diffraction is the limit then the number of features per mm that can be distinguished on the sensor (film or digital) is the same at a given f-ratio irrespective of whether the lens is a 600mm wildlife monster or a 20mm wide angle. As the sensitive surface gets bigger more features can be resolved in the image at the same diffraction-limited f-ratio -- hence the advantages of large format. BTW: some of these very high pixel count phones that are coming onto the market are verging on pointless as even with a lens of about f/1.2 the Airy disk is comparable to the Bayer cell in size.

Sorry if I'm getting horribly technical, but I've spent most of the last 2 years trying to model Fresnel diffraction in coronagraphs.
 

martin henson

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A bit over my head James, but I take your word for it, a lens for me is just a tool in whatever way I use them, leave the rest to you tech gurus :)
 

David M

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James,
Thank you for your exposition. From working with pinholes, I'd somehow gathered that diffraction was related to the absolute size of the aperture, not the f-number. Not much use in the field, but good to lose a misconception.
Now we know how much you know, we shall probably be asking questions...

(Fresnel lenses in astronomy?)
 
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