Voigtlander 25mm at varying f-stops

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Barry_Green

Moderator
Sometimes people say the Voigtlander gets "soft" at wide-open, and on chart testing I can verify that it's not quite as sharp, nor has it got quite the same contrast as when stopped down. But how much difference does it really make? Got curious, so I put it through its paces. First picture is at F/0.95, second is at F/1.4, etc., all the rest are successively one stop deeper. I used the shutter speed to compensate for exposure.

I did have to fudge a little with the f-stop to get it to exactly match the brightness of the previous shot sometimes, but ... eh, it's in the ballpark...

Anyway -- is the Voigtlander unnecessarily soft at wide open? How much difference does an f-stop or two make as far as contrast, sharpness, and DOF? Here's some pix, make your own evaluations. :thumbsup:


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The background is horribly soft at wide open Barry! :Drogar-BigGrin(DBG)


Quick question: for the f0.95 shot (and others) did you focus on the eyes or if not where was your exact focal plane set to?
 
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Shooter said:
It concerns me that you have one of these to do this test with Barry !
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As said before, I ran out of daughters, they all grew up and moved away, so when I get it in my head to run silly tests, this thing is what I use. Thirty-five bucks off ebay.
 
To me f1.4 looks as sharp as f2.8

Unfortunately with f0.95 because the dof is so short and the image is a bit darker one cannot say how the sharpness compares to the others. It does look slightly softer but is that because there are only a few spots in the image that are actually in sharp-sharp focus?

I have shot at f0.95 many times and am very happy with the results. I've said it again and again - I love this lens in fact it's pretty much the one I use the most.
 
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Okay, so here's the weird thing -- the shot at f/0.95 isn't any darker. It was exposed at the exact same level, as determined by the 70-ire zebras on her left cheek. The darkening that you see isn't due to illumination, I don't think. It's more likely due to the contrast getting all washed out. But at f/0.95 things are just ... different. Look at the color of the skin -- on all the other shots it's quite consistent, but on the f/0.95 shot it gets just a little bit more magenta. And the background is noticeably darker on the f/0.95 shot than on any other. It's weird.

And yes, at 1.4 it seems to me like it's as sharp as it gets.
 
You know what's weird... but at f0.95, aside from the color cast you are seeing, it looks like the image is vignetting. How is that even possible? But, it does appear to my eyes that way.

Would love to see the waveform of f0.95 VS f1.4 if you still have the shot set up.
 
Steve Kahn said:
You know what's weird... but at f0.95, aside from the color cast you are seeing, it looks like the image is vignetting. How is that even possible? But, it does appear to my eyes that way.
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Appears to mine that way too...

Would love to see the waveform of f0.95 VS f1.4 if you still have the shot set up.
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It's long since gone, but you can drag the jpgs into Premiere or FCP or whatever and look at what its waveform tells you.
 
Take your V outside and point it at the sky, and use the ND filters to reign it in, and check out the waveform at 0.95 and at 5.6... you'll see the same thing. It has a bit of a porthole effect at maximum wide open.

Now, let's keep in context that our other choices for 0.95 are the Leica at $10,000 and the Noktor which does get substantially softer, and I still think the Voigtlander is a screaming buy. But there does appear to be a little bit of loss of quality when absolutely wide open. Of course, every lens I own behaves similarly (they're never as good at wide-open as they are a stop or two down from wide open).
 
You used the shutter to control the exposure in conjunction with the iris.

Maybe its a Reciprocity Factor?
 
The periscope effect is very odd.

Another question Barry: is this with or without the screw-on lens shade?
 
Digital sensors are designed to be sensitive to rays of light hitting at a perpendicular angle. The rays that such a wide aperture "add" to the exposure hit the sensor so obliquely that they don't even get registered by the photosites. This is called sensor light loss, when super fast lenses start getting into diminishing returns. The Canon users who bought the 50mm f/1.2 wishing to add half a stop over the f/1.4 paid 1000$ difference for light that gets lost at the sensor and are actually getting an additional iso boost (with whatever noise this causes) to hide this fact.
That's the ugly truth http://www.luminous-landscape.com/essays/an_open_letter_to_the_major_camera_manufacturers.shtml
And that's what I think might be happening in your first shot. It doesn't look like a deal breaker over such a beautiful lens anyway.
 
Light at the periphery is getting lost, but on the subject, no -- it really is a full stop faster than when at f/1.4. But yes, there's some manner of portholing or vignetting of light at the edges.
 
Thanks Berry for doing this test. I can live with the image at 1.4. Not liking 0.95. I will avoided it. The color can be fixed but the vignette is tough.
 
The Voigtlander is two lenses in one.

From f/1.4 up it is a lovely standard prime lens, nice and fast, nice and sharp.

At f/09.5 it has a lot more "character", shall we say. I'm biased, I happen to like it (I often add vignette in post!)

Yes, it vignettes. It also has appreciable coma causing glow around light sources- see some of Michael Reichmann's shots at:
http://www.luminous-landscape.com/reviews/lenses/voigtlander_f095_25mm_micro_43_nocton.shtml

These are common characteristics of many lenses, especially ultra-fast lenses, when they are wide open. The amazing thing is how wide the Voigtlander goes given its bargain basement price.

But also take a look at MR's shot of the girl framed by the pillars. That's just beautiful.

I say embrace the character of the lens and accept that at f/0.95 it is a whole different animal from what it is at f/1.4. It'll give your footage a different look but it'll also let you capture stuff that would otherwise be out of reach. If you don't like the way it looks- just stay away from that last stop on the aperture ring. You still have a beautifully made mechanically focussed optically sweet fast standard f/1.4 25 mm lens in native micro four thirds mount, much faster and cheaper than a CP.2.

Cheers, Hywel
 
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