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Forum: Pentax News and Rumors 11-08-2018, 10:13 PM  
Irix Dragonfly 150mm Macro
Posted By Class A
Replies: 156
Views: 24,898
Thanks! I'll send you a a PM.
Forum: Pentax News and Rumors 11-08-2018, 03:18 AM  
Irix Dragonfly 150mm Macro
Posted By Class A
Replies: 156
Views: 24,898
Let me know if you are looking for a buyer. :)
Forum: Pentax News and Rumors 09-25-2018, 07:29 PM  
Irix Dragonfly 150mm Macro
Posted By Class A
Replies: 156
Views: 24,898
So?

Newtonian mechanics are an approximation of Einstein's special and general relativity. Nevertheless, we continue to use Newtonian mechanics very often despite the errors entailed. Or are you considering time dilation, length contraction and relativistic mass when calculating properties of a car trip?

The reason why we can neglect the ramifications of special and general relativity in a lot of situations is because the terms that make a difference make extremely small contributions when speeds are low and space curvature is nearly flat.

The same applies to specialised DOF formulas. For very large and very small distances certain contributing terms become so small that it is entirely safe to ignore them.


No.

Absolutely no risks involved. The errors implied by using the approximation are so small that they can be neglected.

Already at portrait distances, the error is in the 1% range. The whole DOF concept is so fraud with (outdated) assumptions and approximations even for the exact formulas that it doesn't make any sense whatsoever to warn about "risks" when using the magnification-based approximation DOF formula for macro photography.
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