Fred Miranda wrote:
---------------------------------------------
The lens appears well corrected for spherical aberration, but there is still some off axis "coma" visible. What you are seeing in the extreme corners is coma rather than ghosting or flare. Combined with a bit of astigmatism, it creates that particular look. For reference, less corrected designs like the Voigtlander Classic 35mm f/1.4 Nokton and the Leica 35mm f/1.4 Summilux show even stronger coma in the far corners.
That Classic is a good visualization of a hard night out on the town
Fred Miranda wrote:
---------------------------------------------
The lens appears well corrected for spherical aberration, but there is still some off axis "coma" visible. What you are seeing in the extreme corners is coma rather than ghosting or flare. Combined with a bit of astigmatism, it creates that particular look. For reference, less corrected designs like the Voigtlander Classic 35mm f/1.4 Nokton and the Leica 35mm f/1.4 Summilux show even stronger coma in the far corners.
Well the result of coma is ghosting and „flaring“ of point light sources. Nikon engineers often describe it as „off-axis flare" or "sagittal coma flare“ in their 1001 nights stories. We all mean the same thing, but yes coma is probably the most precise term
I don't ever do tests like this on my lenses, but I threw some distant houses into a similar test on my 40/2 Ultron just to see how it behaves wide open. Impossible to say if it's better or equal to the Septon without A/B shots, but I'll get to that in April. Either way, looks fairly similar.
This looks like the perfect lens for the A7CR. I don't know what focus aids you get with Sony, but that is a match. It may also be the only CV lens that looks better in Sony mount than Z...
I wish Nikon had a 1lb/500g full frame body (with dials) to go with this. It would still look like a it has a manhole cover stuck on, but it'd be a handy rig.
Odd I know, but I would be interested to know how the E-mount version performs adapted to Z-mount. My E-mount CV 50/1.2 works fantastically well, but I haven’t had much luck with wider lenses. My Sigma 35i in particular seems to perform markedly worse at wider apertures on my Zf than it does on my A7IV.
It’ll go good with the rumored Z3, full frame Z30/ZR mini.
taildraggin wrote:
This looks like the perfect lens for the A7CR. I don't know what focus aids you get with Sony, but that is a match. It may also be the only CV lens that looks better in Sony mount than Z...
I wish Nikon had a 1lb/500g full frame body (with dials) to go with this. It would still look like a it has a manhole cover stuck on, but it'd be a handy rig.
I wonder why used A7RII for image quality test instead of A7CR?
The lens seems has decent center sharpness for portraits at F2, and at f5.6 has the peak sharpness with quite excellent results considering the lens size. This is the kind of lens I'm truly thirsty on e-mount, a pancake lens with high build quality and good optical performance.
Still miss a the photographic centric A7CR with high resolution EVF and high res. tilting screen, added eye assist MF.
That makes sense in terms of sagittal flare, so sure!
fjablo wrote:
Well the result of coma is ghosting and „flaring“ of point light sources. Nikon engineers often describe it as „off-axis flare" or "sagittal coma flare“ in their 1001 nights stories. We all mean the same thing, but yes coma is probably the most precise term
Lukacs wrote:
I wonder why used A7RII for image quality test instead of A7CR?
The lens seems has decent center sharpness for portraits at F2, and at f5.6 has the peak sharpness with quite excellent results considering the lens size. This is the kind of lens I'm truly thirsty on e-mount, a pancake lens with high build quality and good optical performance.
Still miss a the photographic centric A7CR with high resolution EVF and high res. tilting screen, added eye assist MF.
Hi Luka,
My A7CR has been converted by Kolari Vision to a Leica M sensor stack, so it’s no longer suitable for resolution tests or any evaluations with E mount lenses. Because of that, I use the Sony A7R II 42MP body exclusively when testing E mount glass.
Maximilian wrote:
Did Fred ever make a review of the Sony G 2,5/40mm?
I cannot find any in the archives.
I owned the Sony 40mm f/2.5 G in the past but never formally reviewed it. It's a great AF lens, but f/2.5 is much closer to f/2.8 than to f/2 in real light transmission and depth of field.
Since I already own the TTArtisan 40mm f/2, I chose to test that one against the new CV 40mm f/2 instead, especially since the same lens is also offered in Nikon Z mount, just like the Voigtlander Septon.
Infinity Resolution and Contrast on Sony A7R II (42MP) compared to Voigtlander 40mm f/2.8 Heliar
The Voigtlander 40mm f/2.8 Heliar is fundamentally an M-mount lens, designed to be used on E-mount bodies with Voigtlander's close-focus adapter to work as a helicoid. It's carefully optimized for the Sony E-mount sensor stack, and it performs impressively given its super-compact pancake form and minimal element count, much like the Septon, which follows the same philosophy: very small and lightweight, yet delivering strong image quality.
Comparing the Heliar to the Septon is interesting. Since I own the Heliar, I wanted to see what Cosina achieved relative to the Septon. Overall, the Heliar holds up well, but the Septon has an advantage in both center and edge performance. The Heliar performs better in the mid-field, which could be a result of field curvature, a factor I plan to test next.
The extreme corners never quite reach their best with the Heliar, whereas the Septon delivers excellent corner sharpness once stopped down after f/4.
Below is the full image thumbnail indicating the area shown at 1 to 1 magnification.
Distance: Infinity
Camera: Sony A7R II
Focus: Center - Best of three @ 12.4x magnification
Infinity Resolution and Contrast on Sony A7R II (42MP) compared to Voigtlander 40mm f/1.2 Nokton at f/2
The Voigtlander 40mm f/1.2 Nokton is a much larger lens, so it's perhaps not a completely fair comparison to the new Voigtlander 40mm f/2 Septon, especially since the Nokton will be compared stopped down to f/2, which naturally improves performance. Still, the Nokton is a lens many shooters own and love, so it makes a useful benchmark for what to expect from the 40/2 Septon.
To my surprise, the Septon keeps up very well with the 40mm f/1.2 Nokton at f/2, even though the Nokton is stopped down. They are very similar across the frame, though the Nokton shows less vignetting in the corner crops. This is not surprising since I did not correct for vignetting or color aberrations and the Nokton is stopped down from f/1.2 to f/2 while the Voigtlander 40mm f/2 Septon Aspherical is wide open.
The Nokton only shows a real advantage in the mid-field at f/2.8 and smaller apertures, not wide open, and in the extreme corners at wider apertures like f/2 and f/2.8. By f/4, their performance is very similar across the frame, except for the mid-field difference, which I suspect is due to field curvature and still needs to be tested.
This says a lot about the pancake Septon. I honestly expected the Nokton to outperform it by a wide margin, but that clearly is not the case.
Below is the full image thumbnail indicating the area shown at 1 to 1 magnification.
Distance: Infinity
Camera: Sony A7R II
Focus: Center - Best of three @ 12.4x magnification
At Mid-field Infinity Resolution and Contrast on Sony A7R II (42MP) compared to Voigtlander 40mm f/1.2 Nokton at f/2
Here you can clearly see some field curvature, possibly with a wave-like shape at this distance, as the focal plane in the Septon crop appears to shift closer to the camera.
The Voigtlander 40mm f/2 Septon Aspherical shows an interesting field curvature pattern, which I suspected from the resolution and contrast tests where I focused at the center and did not refocus for the mid-field or corners. The mid-field appears weaker compared to other 40mm lenses, and the reason is field curvature.
That is actually good news. If you focus on the mid-field area, the weakness disappears. It is not a lack of resolution, but a change in the shape of the focal plane depending on subject distance. Pancake lenses usually compromise field flatness, so this is not a surprise.
At close range, I see a more outward curvature with a slightly wavy character. As you move toward mid and longer distances, that wave shape, almost like a W, becomes even more apparent. The best way to understand it is to visualize the field curvature from 0.7m to infinity in small increments in the GIF animation below:
For anyone who enjoys well-defined sunstars, the Voigtlander 40mm f/2 Septon Aspherical shines. Like most Cosina lenses, it features straight aperture blades, and thanks to precise manufacturing tolerances, the sunstars it produces are clean and evenly spaced.
Well-formed sunstars begin to appear as early as f/2.2, just a third of a stop from wide open, though their definition improves noticeably from f/2.8 onward. At f/2, the sunstars are soft because the blades are fully open, while at the smallest aperture, f/22, they become chaotic and unattractive. Every aperture in-between produces some level of sunstar definiltion.
The series below illustrates the sunstar shape from f/2 to f/22 in one-stop increments (Also f/2.2 and f/2.5 intermediate ones). With 10 straight blades, this lens produces 10-point sunstars that remain symmetrical and visually pleasing.
Flare control is very good but not exceptional. Some ghosting occurs when pointing the lens directly at the sun or bright light sources, but it is moderate and rarely distracting.
This series also provides a look at vignetting and how the lens handles flare across different apertures.
