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My medium format digital journey - Fcousing

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Article Index
My medium format digital journey
raw images for download
Where do I stand now
The experience
Color Profiles
Resolution Tests
Real World Samples
Color rendition
Dynamic Range
Moiré & aliasing
DoF and diffraction
More real world images
Three format comparison
Diffractio series
The lenses
Fcousing
The Bad News
Capture One or LR 4.4
Some comments on Phase One business model
The Ultimate Platform?
All Pages

Focusing


I have three different focusing hoods. The standard focusing hood:



The PM5 - prism viewfinder

The PM5 can be combined with a Zeiss Victory 3x12 monocular, this combo yields a 9X magnification and the monocular can be adjusted to individual eyesight.



The Hartbley 4X loupe is very good and can be adjusted to individual eyesight.





Clearly, my favorite is to use the PM5 with the Zeiss monocular.

The image belows shows a crop of a large image with a small USAF-type test target. I looked at USAF-target in the viewfinder which group could be clearly resolved in the viewfinder.

PM5 - red frame
Hartbley - blue frame
PM5 + monocular yellow frame 



The standard viewfinder loupe actually worked very well, but I cannot give a figure for that one.

Clearly, lens/sensor has much higher resolution than the viewfinder, even with the 9X PM5/monocular combo. So focusing will not be based on resolution alone but on conceived contrast. 

My viewfinder has also a split edge. This is probably very accurate as it takes help of the vernier acutance of human vision. The split edge is very consistent with the PM5+monucular combo. The problem with split edge is the it needs very good and clear edge to focus on, like a flagpole. It landscape photography it is pretty difficult to find such good edges. This is an area where live view manual focus at actual pixels has a great advantage. On the other hand, most lenses may have residual aberrations and even focus shift making live view focus harder.

Discussion

To me it seems that my findings essentially confirm what could be expected from the MTF curves published by Zeiss. The Sonnar 150/4 is excellent at all aperture while the other lenses need to be stopped down for good corners. Mostly I shoot at f/11 - f/16, because I want good DoF, that will probably loose some sharpness at center but makes fo decent corners. Stopping down also reduces moiré (acts as an aliasing filter).



Last Updated on Thursday, 08 August 2013 12:38  

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