07-26-2012, 02:41 PM
(This post was last modified: 07-27-2012, 07:38 AM by Ballonseide.)
Hi there,
I recently bought a (new) Voigtländer Nokton 58/1.4 from Hong Kong (Pentax mount). It's a great lens, but I am puzzled by its behavior at large apertures. Maybe someone here can help me understand this.
The problem: Images shot at f/1.4, f/1.6 and f/1.8 look identical. I noticed this because (1) the size of background highlights doesn't change anymore when you stop further down from f/1.8, and (2) f/1.4 gives noticeably underexposed results. I first thought this might be a defect of my copy, but if you look at the bokeh test images in the [url="http://www.opticallimits.com/nikon--nikkor-aps-c-lens-tests/360-voigtlander-nokton-58mm-f14-sl-ii?start=1"]Photozone review[/url], they show the same thing concerning highlights. Even the difference between f/1.4 and f/2 is negligible in those test shots.
I went on and shot a series of images with only the aperture varying between shots. f/1.4 through f/1.8 expose identically, for all practical purposes. Yet visual inspection (i. e. looking into the lens while shooting) shows that the aperture opens up completely at f/1.4, a little less at f/1.6 and less again at f/1.8. So both a mechanical defect and a problem with the electronic aperture control are unlikely. (I can't reproduce the effect manually since the aperture ring does not allow a value between f/1.4 and f/2.)
Does anyone have an explanation for this? I was already about to send the lens in for service, but if this is "normal" behavior that probably wouldn't do much good.
Best regards,
Sebastian
I recently bought a (new) Voigtländer Nokton 58/1.4 from Hong Kong (Pentax mount). It's a great lens, but I am puzzled by its behavior at large apertures. Maybe someone here can help me understand this.
The problem: Images shot at f/1.4, f/1.6 and f/1.8 look identical. I noticed this because (1) the size of background highlights doesn't change anymore when you stop further down from f/1.8, and (2) f/1.4 gives noticeably underexposed results. I first thought this might be a defect of my copy, but if you look at the bokeh test images in the [url="http://www.opticallimits.com/nikon--nikkor-aps-c-lens-tests/360-voigtlander-nokton-58mm-f14-sl-ii?start=1"]Photozone review[/url], they show the same thing concerning highlights. Even the difference between f/1.4 and f/2 is negligible in those test shots.
I went on and shot a series of images with only the aperture varying between shots. f/1.4 through f/1.8 expose identically, for all practical purposes. Yet visual inspection (i. e. looking into the lens while shooting) shows that the aperture opens up completely at f/1.4, a little less at f/1.6 and less again at f/1.8. So both a mechanical defect and a problem with the electronic aperture control are unlikely. (I can't reproduce the effect manually since the aperture ring does not allow a value between f/1.4 and f/2.)
Does anyone have an explanation for this? I was already about to send the lens in for service, but if this is "normal" behavior that probably wouldn't do much good.
Best regards,
Sebastian