ZHNL Posted February 4, 2017 Share #1 Posted February 4, 2017 Advertisement (gone after registration) I have a question about Leica S APO_ELMAR 180mm, at WO f3.5, when I hit the DOF preview, I can see the aperture blade actually close some instead of WO. To verify further, I tried at f4, it is indeed close a little bit further and each stop will close more. Can you guys who have this lens check. I took an image WO, and look through the lens, I can see the aperture indeed close a little before shutter close. From what I guess, if the exposure indeed at f3.5, the lens most likely f2.8 if not close. The reason I find this out is I notice bokeh light source ball is not fully rounded at WO. Link to post Share on other sites More sharing options...
Advertisement Posted February 4, 2017 Posted February 4, 2017 Hi ZHNL, Take a look here Leica S APO_ELMAR 180mm aperture. I'm sure you'll find what you were looking for!
John McMaster Posted February 4, 2017 Share #2 Posted February 4, 2017 Looking at the lens, I can see the same on mine...... john Link to post Share on other sites More sharing options...
jip Posted February 4, 2017 Share #3 Posted February 4, 2017 The lens is probably a bit wider than 3.5 and to make the exposure equal on all lenses they stop down the lens super slightly to get to exactly 3.5 (the 35mm Summicron-M ASPH. has the same, you can turn it a bit below f2.0 and you can see the aperture widen up even a bit more.) More lenses have this... Link to post Share on other sites More sharing options...
ZHNL Posted February 4, 2017 Author Share #4 Posted February 4, 2017 The lens is probably a bit wider than 3.5 and to make the exposure equal on all lenses they stop down the lens super slightly to get to exactly 3.5 (the 35mm Summicron-M ASPH. has the same, you can turn it a bit below f2.0 and you can see the aperture widen up even a bit more.) More lenses have this... Thank you guys for your reply. If it is mainly for exposure consistency, Then why not a f2.8 lens from beginning? M lens I see having this is 75mm summarit, that lens aperture physically not fully opened. This one is different, it was designed full opened but only close at the time you made exposure. The lens has insane performance, it is not just sharpness, the fidenlity is best of S glasses I have seen. But bokeh highlight will be handicapped because of this. A pity. Link to post Share on other sites More sharing options...
jip Posted February 5, 2017 Share #5 Posted February 5, 2017 Because this is not an M lens but SLR lens having the tiny bit of extra brightness while focussing is a pro, not a con. So they designed it this way that it only stops down to the exact f/3.5 when you make your exposure. Link to post Share on other sites More sharing options...
Paul J Posted February 5, 2017 Share #6 Posted February 5, 2017 I agree, it's off putting i the aperture isn't round on a lens of such calibre. Link to post Share on other sites More sharing options...
ZHNL Posted February 5, 2017 Author Share #7 Posted February 5, 2017 Advertisement (gone after registration) Because this is not an M lens but SLR lens having the tiny bit of extra brightness while focussing is a pro, not a con. So they designed it this way that it only stops down to the exact f/3.5 when you make your exposure. That is not tiny bit, I feel it is about half~one stop there. I don't think bright a little bit is a 'pro' compare to a true f2.8 lens if the design is f2.8 capable. I am surprised because most Leica tele lens will be able to cover bigger sensor, so for whatever technical reason, limit it at f3.5 is a surprise for me. Especially, at certain condition, Bokeh will be suffered, not to mention a little more exposure freedom. Anyway, the intention of the thread is asking if it is normal for the lens, I get what I need. Thanks. Link to post Share on other sites More sharing options...
albertknappmd Posted February 7, 2017 Share #8 Posted February 7, 2017 I never noticed it before but.. given the lens' stellar optics and performance.. I don't care!!! Albert Link to post Share on other sites More sharing options...
BernardC Posted February 7, 2017 Share #9 Posted February 7, 2017 The fact that the aperture mechanism stops-down a bit at 3.5 doesn't necessarily mean that the lens is faster than 3.5. It could be that the aperture mechanism is slightly bigger than the optical diameter of the lens. One possible reason for this is that they use the same part in other lenses, such as the 100/2.0. There is no benefit in designing, manufacturing, and stocking two different aperture mechanisms that differ by a few millimetres. Link to post Share on other sites More sharing options...
jip Posted February 8, 2017 Share #10 Posted February 8, 2017 There is no benefit in designing, manufacturing, and stocking two different aperture mechanisms that differ by a few millimetres. At this price point it would be beneficial as to achieve full round aperture wide open, if what you are saying is indeed the case. Link to post Share on other sites More sharing options...
alan.y Posted February 8, 2017 Share #11 Posted February 8, 2017 I seem to remember the Summicron-S (I no longer own it) being slightly "stopped down" at f/2 also. Link to post Share on other sites More sharing options...
ZHNL Posted February 9, 2017 Author Share #12 Posted February 9, 2017 I seem to remember the Summicron-S (I no longer own it) being slightly "stopped down" at f/2 also.I checked that my 100cron doesn't do that. It is not really close any more at f2 when you do DOF preview. Link to post Share on other sites More sharing options...
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