CheshireCat Posted January 11, 2013 Share #1 Â Posted January 11, 2013 Advertisement (gone after registration) Just bought a brand new Voigtlaender Heliar 12mm f/5.6 II. Checking the aperture, looking at the back of the lens, I see that the blades are still very visible wide open. No round aperture at all. Conversely, on my old Heliar 15mm f/4.5 the blades totally disappear wide open. Â Is this normal ? Link to post Share on other sites More sharing options...
Advertisement Posted January 11, 2013 Posted January 11, 2013 Hi CheshireCat, Take a look here 12mm Heliar aperture problem ?. I'm sure you'll find what you were looking for!
trylab Posted January 11, 2013 Share #2 Â Posted January 11, 2013 On my brand new 15mm Heliar M, I also see 1mm of the blades wide open at f/4.5. Â Best Regards Link to post Share on other sites More sharing options...
Lindolfi Posted January 11, 2013 Share #3 Â Posted January 11, 2013 Yes, that is normal in the Voightlander 12/5.6. It is the same in super wide angle lenses in large format photography (Schneider and Rodenstock) Â When you remove both caps, turn to f/5.6 and hold the lens in front of you, while turning side to side, looking though the lens from the front, you will see that the aperture seems to move, hardly changing in shape but becoming larger when the lens is tilted. This is due the design. All is part of the fight against light fall-off in this super wide design. Â If the aperture would have been larger, it would get obstructed partly when tilting the lens, enhancing light fall off. Â If you really want to know if f/5.6 in this lens is truly f/5.6, simply photograph a white surface, keeping the exposure so that the histogram has a peak in the middle. Maintain that exposure and phototograph at f/5.6 with a 50 mm for instance and check whether the histogram of the middle section of the image is in the same area of brightness values. (You can do this in PhotoShop). Â After that, go and take photographs with this wonderful lens. Link to post Share on other sites More sharing options...
Lindolfi Posted January 11, 2013 Share #4 Â Posted January 11, 2013 Just performed the experiment I suggested above with the 35/2.0 Summicron ASPH and the Voigtlander 12/5.6, both at f/5.6. Same exposure time and ISO. Indeed, the means of the histograms of a section from the middle are less than 1 bin apart. Â http://www.photoplaza.nl/lindolfi/compareaperture35and12.png Link to post Share on other sites More sharing options...
CheshireCat Posted January 11, 2013 Author Share #5 Â Posted January 11, 2013 Thank you guys ! Great suggestion about the histogram check. Will test the lens tomorrow. Link to post Share on other sites More sharing options...
tobey bilek Posted January 12, 2013 Share #6 Â Posted January 12, 2013 My screw mount 12 has perfectly round blades wide open and you can see a considerable amount of them. Â I manually code as 21 28 pre ASPH on the M9 and get no cyan corners, but they do vignette some. Usually I will overexpose 1/2 stop and pull the center back. That way the corners do not get noise. Â If you change nothing, the center will be perfect with dark corners. The 15 is a better lens in this regard, but my screw mount version still gets dark corners. Link to post Share on other sites More sharing options...
jankap Posted January 12, 2013 Share #7 Â Posted January 12, 2013 Advertisement (gone after registration) My screw mount version also shows a (very) round f-stop at 5.6 by turning the lens from side to side. We should not forget, that an f-stop of 5.6 at 12mm means an opening of only 2.1 mm (12 div 5.6). It is a nice lens (for the Ricoh), but the DOF markings are too optimistic. Jan Link to post Share on other sites More sharing options...
honcho Posted January 12, 2013 Share #8 Â Posted January 12, 2013 ....It is a nice lens (for the Ricoh), but the DOF markings are too optimistic. Â It's also a nice lens on my MP. Â With a focal length of 12mm and detents at .5 and 1m on the focus ring, the dof scale could be in Chinese for all I care. Â (OP: The diaphragm blades and round hole you see at f5.6 from the rear is as it should be). Link to post Share on other sites More sharing options...
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