Voigtländer Nokton 25mm F0.95 Corner Sharpness
Sunday, December 5, 2010 at 16:58 ;)
crop sizes and locationsWide open and at moderate apertures, the Nokton's images display an abrupt loss of sharpness in the extreme corners of the frame. Of course there needs to be fine detail in the corners and the corners have to lie within the zone that's in focus before it's noticeable. Is it a problem? That depends on how you want to use the lens. The blurring doesn't extend very far into the frame, so cropping is one solution. I intend to use this lens wide open or stopped down slightly most of the time. In that scenario the part of the image that's in focus is so shallow that the corners are irrelevant. Most of the time I wouldn't use the Nokton for scenery where corner sharpness is an issue. I have more compact and wider lenses for that. The Voigtländer Nokton is a low light specialist.
I did, however, want to determine how far the Nokton would have to be stopped down before corner blurring becomes negligible. It's good to know for those – even if rare – photos where corner sharpness is relevant. The test sequence was done with the camera on a tripod using the self timer. I also did a comparison with the Lumix 20mm F1.7 pancake lens which is known to be quite a sharp lens. Obviously, with the wider angle of view, I had to move closer to the subject in order to frame an area similar to what the Nokton's 25mm were capturing.
100% cropsThe 100% crops above (all developed in Lightroom 3 with the same, fairly neutral settings) show an incremental increase in corner sharpness upon stopping down. At which point it becomes acceptable will vary depending on who's scrutinizing the photos. Viewing the entire photo on my 24” screen, I'd say that corner blurring is reasonable by F5.6 and barely noticeable at F8.0. Again, I'm not judging zoomed in, 100% crops like the ones posted above but photos displayed to fill the screen.
The central crops above show that the Voigtländer lens is sharper than the Lumix lens. This is even true over the majority of the frame. Only the extreme corners are worse in photos taken with the Voigtländer Nokton.
For those interested, I've posted all the RAW files that the above crops were taken from.
Lumix 20mm at F4
Nokton 25mm at F4
Nokton 25mm at F5.6
Nokton 25mm at F8
Nokton 25mm at F11
Reader Comments (4)
Bjorn, take a look at Luminous Landscape review of the lens.. very interesting. $900 vs. $300 lens.
Hi Joan. Yes, I've seen Michael Reichman's first impressions review.
These crops don't tell the whole story of course. The Nokton is a specialized lens and I could also do image quality tests with the Lumix at F1.7 and the Voigtländer at F0.95. That would result in quite a difference in ISO and DOF. I like both lenses a lot. One for quick snaps on the "street," the other for more considered low light shooting and/or shallow depth of field shooting.
I want to be able to use my fast lens not only in the dark but also as a normal lens for general use. For example, when traveling you probably don't want to carry several 25mm lenses...
So, for me this was an informative and interesting entry. Thank you.
You're welcome, Jonas. Personally, I wouldn't hesitate to travel with only the Voigtländer.