NEX-7 Part 2: Corner Performance with Zeiss Biogon T* 35mm F2.0 ZM
Saturday, January 7, 2012 at 13:05 ;)
Central and corner crop locationsThis is my “brick wall.” It's a little more colourful and has the benefit of a lot of unobstructed space in front of it. Still, I'll admit that it's not that much more interesting than endless rows of bricks. But it serves a purpose: I'm trying to find out if corner image quality deteriorates when using the Zeiss Biogon 35mm F2.0 on the NEX-7 as opposed to the NEX-5N. It's been reported that the NEX-7 sensor has more difficulty with some wide angle, Leica M-mount lenses than the sensor in the NEX-5N. The 35mm Biogon isn't really that wide, so it shouldn't pose too many problems for the NEX-7. Others have reported reduced corner resolution and a magenta colour cast with wider lenses though.
The purple facade isn't really suitable for checking for the magenta colour cast, but there's a lot of fine detail for evaluating sharpness. I haven't really noticed any objectionable colour casts in the other photos I've taken with the 35mm Biogon on the NEX-7 though.
To find out if there is a discernible difference between how the Biogon performs on these two cameras, I took advantage of the unexpected break in the poor weather take a series of test photos. Photos with both the NEX-7 and the NEX-5N were taken as RAW files, with the cameras mounted on a tripod and the self timer was used to release the shutter. The exposure settings were identical on each camera, with only slight variations in light levels between photos. But that's par for the course when you want to avoid difficult to relate to photos of paint brushes and test charts. To reduce focus errors, I took 3 photos at each aperture with each camera, refocusing in between shots. Processing the RAW files in Lightroom, I selected the sharpest photo of each set. The RAW files were then exported as TIFF files and I resized the NEX-5N images to match the pixel dimensions of the NEX-7 image (6000 x 4000).
If you want to use a different method to compare the output, you can download the original RAW files under each of the corner crops.
The following 100% crops are from the central portion and upper right corner. The F2.0 images are overexposed since I hit the 1/4000s second shutter speed limit.
;)
The NEX-7 F2.0 (not posted here) and the F2.8 corner crop above are very similar. Do I see a slight magenta colour cast? This is the extreme corner and therefore the worst possible case scenario. Things improve rapidly as you move into the frame.
NEX-5N + CZ Biogon 35mm F2.0 at F2.0 RAW file note: possible focus error
NEX-5N + CZ Biogon 35mm F2.0 at F2.8 RAW file
NEX-7 + CZ Biogon 35mm F2.0 at F2.0 RAW file
NEX-7 + CZ Biogon 35mm F2.0 at F2.8 RAW file
;)
Above: marginal differences at F4.0
NEX-5N + CZ Biogon 35mm F2.0 at F4.0 RAW file
NEX-7 + CZ Biogon 35mm F2.0 at F4.0 RAW file
;)
Above: NEX-7 corner is sharper from F5.6 compared to the "uprezzed" NEX-5N file.
NEX-5N + CZ Biogon 35mm F2.0 at F5.6 RAW file
NEX-5N + CZ Biogon 35mm F2.0 at F8.0 RAW file
NEX-7 + CZ Biogon 35mm F2.0 at F5.6 RAW file
NEX-7 + CZ Biogon 35mm F2.0 at F8.0 RAW file
;)
;)
;)
Above: the central portions of the NEX-7 image show more detail from F4.0 compared to the same crop from the "uprezzed" NEX-5N files.
Conclusion: The Carl Zeiss Biogon T* 35mm F2.0 ZM delivers excellent sharpness on the NEX-7. While the extreme corners and, to a lesser degree, the left and right edges of the frame are softer at large apertures (F2.0/2.8), the increased resolution over most of the frame makes up for the softer corners. Corner resolution is not usually all that field relevant at large apertures anyway. At F4.0, the 24 megapixel sensor is no longer at a disadvantage in the corners and at F5.6 and F8.0 the NEX-7's images have superb levels of detail throughout the frame.
The corners of the NEX-7 frame also show a stronger magenta cast, especially at larger apertures. In some case the color shift is objectionable and I have to correct the images in CornerFix. The magenta cast becomes visible if one or more of the corners are very light and have little color of their own.
Still, overall I think the Zeiss 35mm F2 Biogon remains a good choice for the NEX-7. I continue to be impressed by the sharpness as well as the contrast, colours and character of the images produced by this little Zeiss lens.
Reader Comments (19)
Thanks for the test Björn, looks like the NEX-7 will not work for me if even a 35mm lens needs stopping down to f5.6 to get acceptable corners.
Can't see the CV 15mm, the GR 28mm and even the CV Nokton 35mm f1.2 working on the NEX-7 but we can try these out next time we meet.
So far the GXR seems best for M lenses but the NEX-5n could make for a nice backup camera. Will wait to see what else is coming out from Fuji and so on.
Excellent work Bjorn...Very useful...Just what I expected...But you have confirmed it.
Thanks Barry. Maybe over time there will be more and more comparisons and sample images produced by manual lenses on NEX cameras. That way we can be better prepared when the urge to buy another lens strikes again.
Cristian, I don't think I'd want to see what the CV 15mm looked like on the NEX-7. But I'll take you up on your offer to try the CV Nokton 35mm F1.2. Just remind me to give it back to you at the end of the evening ;-)
Personally, I find the corners of CZ 35/2.0 Biogon acceptable at F4.0. My crop shows the extreme corner; resolution improves very rapidly only a little further in. In everyday shooting it's virtually impossible to notice the difference. At F2.0 and F2.8, it's a different story and you need to be careful if you have corner detail in the plane of focus.
The Ricoh GXR is designed for use with M-lenses, so one would expect them to perform well. With the 5N I guess it's more of a fortunate coincidence. Still, I needed more direct control of exposure parameters and the less cramped ergonomics of the 7N. Since the Biogon isn't the worst offender of the M-mount lenses and it's also my only M-mount lens, I compromised some corner performance wide open for the extra features of the 7. I could have gone for the GXR, but I find the tilting screen too useful to buy another camera without one.
I still like the look of the images produced by the NEX-7 and the Biogon, using it just takes a bit more care. My other most used lens, the E-mount Zeiss Sonnar 24/1.8 is designed for NEX and has no such limitations.
The center of the image on the nex 7 certainly looks a lot more appealing to me than the 5n. Much crisper. Thanks for sharing. Still waiting and waiting for my nex 7 which i pre-ordered on August 23rd!
Rishio, yes it's amazing how much fine detail this lens can resolve on the NEX-7. Hang in there, the wait will be worth it.
Yes - i'm set on the Nex 7. I mostly shoot with a 35 and 85 in Full frame so the 24/50 set for the Nex series is perfect for me. I'm pretty much selling off my large Canon gear for this..
I also ordered this $30 35mm f/1.7 fotasy lens for the nex 7 (see review here http://www.seriouscompacts.com/f41/bang-buck-sony-nex-3-fotasy-35mm-f-1-7-a-3294/). It's a fun lens, but I do hope Sony get's to releasing a 35 f/1.4 native soon.
The new Fuji looks like great combination - I'm sure it will get Sony up on their feet. The fuji camera is quite a bit bigger however (see my visual comparsion here: http://forums.dpreview.com/forums/read.asp?forum=1020&message=40260109), looks like it lacks the tilt LCD (a big deal for me!), and probably not as good in video mode which is important for me. I also much prefer the tri-navi handling - makes a lot of sense to me!
Rishio; expertly done visual comparison. For me the new Fuji is too large. Sony are masters at miniaturization, and NEX-7 is pretty much an optimum size and weight: less cramped than the NEX-5N but still small and light enough to have with you all day without making its presence known in a negative way. It's amazing how many features Sony has managed to pack into this little camera. I agree with you, a tilt screen is a vital feature for me as well. There's absolutely no reason why such a large and expensive camera like the Fuji X-Pro 1 shouldn't feature one. But it should, like you say, motivate Sony to release more enthusiast targeted NEX gear.
Hi Bjorn
I don't think I thanked you for sharing - As I do understand the amount of work you put into doing all this....”VERY MANY THANKS”.
Putting my pixel peeping hat on. These are my observations for what they are worth, having downloaded your RAW images and studied them at great length now in LR 3.6 and as DNG in CS4.
My RAW/DNG conversion of the AS SHOT may have been slightly different from yours - ie. Like the amount of sharpening applied etc...So I will remark on what you have taken, rather than my results (not that mine were really any more different from yours).
It was instantly apparent to me that the purple fringing was much more pronounced on the right hand corner shots of the NEX-7 and dissipated itself nearly by F5.6 (Probably partly due to the lack of micro-lenses in the NEX-7 sensor).
Interpolating the NEX5N (16mp's) up to the NEX-7 (24mp's) size images...An increase of 50% (8mp's) of non image detail which is no mean amount when viewing at 100%, should naturally result in slightly softer looking images from the centre to the corners for the NEX5N, with a somewhat reduced masking of the noise. However the NEX5N looked better in the corners all the way up until F5.6 where I suspect the uprezzing of the NEX5N then started to pay the penalty.
The centre of the NEX-7 looks a clear winner - But again I suspect the softness is part due to the uprezzing of the NEX5N images.
My findings were that if you analysed the two of them by reducing the NEX-7 images down to the original NEX5N size there was nothing much between the two of them...If anything the NEX5N was the winner! (but if you owned the NEX-7 why would you want to do this, unless making small prints was the norm I suppose).
As you know I was particularly interested in your results having just purchased the NEX5N and 35mm f2 ZM Biogon this week...I was dithering for a long while between buying the NEX5N or waiting a week or two later for the NEX-7 to arrive in the UK. Based upon downloading NEX5N and NEX-7 images from a variety of places and agonising over the comparisons on the screen and in 24”x16” print form, I decided that the NEX5N was the camera for me, well at least for now. It would be a good stop gap until they have ironed out some of the NEX-7’s sensor problems in future NEX release cameras. Then I could either stay with Sony or even jump ship to Fuji without to much of a financial loss.
The appeal of the NEX-7 to me was in the way the camera handled and that integral EVF. Not so much in any improved IQ (Well not in real world term prints up to 24”x16” - Viewed from the correct distance) as I believe that is swings and roundabouts between the two of them. Thanks again Barry.
Barry,
Yes, it is quite an effort to put something like this together. It starts with standing out in a field with a tripod and having to constantly re-shoot long sequences of images because the light changed. Of course I got to enjoy the good weather for a little longer this way. Comparisons like this help me to understand how I can get the best out of the system I'm shooting with. Sharing the results here is nothing more than what many others have also done for me. I pored over a lot of reviews and user reports before deciding to get the Biogon.
Your strategy of downsizing the NEX-7 images to match the 5N is just as valid an approach. If anything, you can take from my comparison that our Biogon is still more than a match for the latest generation of high resolution sensors. I rarely need that kind of detail, but it's still impressive to see. In any case this lens should be a good investment; not all lenses work well with ever higher resolution sensors. Like you say, maybe over time changes in sensor architecture will improve corner performance.
But I didn't get the NEX-7 for its ability to resolve finer detail. Stronger yet, I was even prepared to take a small step back in image quality to gain the user interface and more comfortable ergonomics. I do an awful lot of shooting, sometimes with paid assignments, and I need better controls and a hot shoe on my main camera. At the same time, I'd still like my kit to be light for everyday use and especially while I'm travelling. Weighing only 575g with the E-mount Zeiss 24mm F1.8, the NEX-7 packs a lot of image quality and a good interface into a light package. I can carry it around my neck all day if necessary without it interfering too much with my other activities. I agree with you 100% when you say that the appeal of the NEX-7 is in how it handles and, of course, the integrated EVF (I'm already finding that an improvement over the clip on one). Image quality might be a little better here, a little worse there, but it's not the main issue.
Well said Bjorne,
Precisely the same reasons I am interested in the Nex 7. While the current image quality meets my requirements, I'm not too worried about those details because I'm buying into a system - not a camera. Sony has the fundamentals (compactness, handling, image quality, technology) right with this camera. More so, Sony knows how to make sensors so no doubt they will improve. Even if the Fuji Pro sensor is way better, it'll be a cat and mouse game and sony will not stand still. More lenses will be added to the lineup as time goes on but the current 24mm f/1.8 and the upcoming 50mm f/1.8 completes the most fundamental pair of lenses that I use (I do wish the 50 f/1.8 was black - but on the bright side, it'll make it clear when i switch lenses which one is which by a quick glance). The only other supplementary lenses I'd like would be a 12mm wide prime, a 35mm f/1.4, and a 90mm telephoto prime. The telephoto is on it's way 2012 according to the roadmap. People are complaining about the Nex lenses, but Sony's getting it right with the introduction of the 24 and 50 (though I would have liked to see the 24 priced closer to $700).
Look forward to getting this camera and putting my post Canon 5d work out there!
Hi Rishio,
There's always a lot of hype when a new sensor technology is introduced. Seldom is the benefit as great as proclaimed nor free of free of any sort of compromise.
Sony will have their own answer. They produce quite a large volume of sensors and have the R&D resources. Like you say, you are buying into a system and Sony has the fundamentals. In my opinion, one of their biggest strengths is their expertise in miniaturization which they've exploited with the NEX camera bodies. Take for example the tilting screen which is flush with the rear of the camera and doesn't appear to make the body any thicker. Or the large, high resolution EVF which doesn't protrude from either the front or rear of the camera (only the removable eye cup).
I like your thinking about the silver color of the 50mm F1.8 lens, even if you're not 100% convinced. Anything that helps when you're fiddling around with lens changes is a plus, whatever it looks like. One of the biggest advantages of the 50/1.8 is the fact that it's stabilized, the only lens of its kind that is (excepting primes on bodies with sensor stabilization).
I agree with you on the need for a wide prime and a the short telephoto that's already on their road map. I fear though that we'll have to wait for the former since Sony will announce a wide zoom first. A 35/1.4 would be very nice although I suspect that Sony will use this focal length to give everyone the pancake lens they've been clamoring for. So perhaps it will be F2.0 or worse.
Looking forward to seeing your shots with the NEX-7. Hope you get it soon.
Hi Bjorn.
Thank you for great test. I am very close to buy Nex 7 with Biogon C 35mm f/2.8 .
Please, could you post any thoughts and ideas about this combo perfomance.
Boris, I haven't used the Carl Zeiss Biogon 35mm F2.8. From what I've seen though, I would opt for the F2.0 version instead - unless you get a very good deal on the F2.8 lens. According to Photozone.de, the 35/2.8 didn't perform as well on the NEX-5 as the 35/2.0. Given that neither the price nor the size and weight differ significantly between the two lenses, I'd opt for the faster one.
Barry, I don't understand your comments about resizing. It's difficult to impossible to compare different sensors at different file sizes. Comparing 100% of Nex 5 to 100% of Nex 7, for the same image, would result in two different views in the crops. Downsizing Nex 7 to match the Nex 5, you are purposefully throwing away resolution, so no surprise that the Nex 5 would be as good at that point. I think most of us probably are happy enough with the resolution of the non-Nex-7 cameras, but there's no denying that more detail can be had from the Nex-7 for those that want it.
Hi GaryW
I thought I had explained it quite well...
I was merely pointing out an alternative way of doing the test for the same size image comparison of the 2 cameras with the same lens (with no cropping) - Either as Bjorn had explained...Which results in adding 50% of non resolution to the NEX5N or by removing 1/3 of the resolution from the NEX7...Neither method is ideal or results in any real truthful comparison...But it is the best we can achieve.
I hope that explains it better for you.
Hi Bjorn.
Finaly get nex 7 and Biogon 35mm f/2. Looks great. Thank you very much for advice.
Unfortunately I couldn't screw completly at B+W 43mm uv filter.
Is this a problem?
Hi Boris,
Congratulations on your new NEX-7 and Biogon. I see you got the F2.0 version after all.
As to the filter, you're probably using a version with a different thread pitch; one meant for 43mm threads on Leica lenses. If it helps, I'm using the B+W 43 010 UV - Haze 1x MRC F-PRO. That fits beautifully.
I would love to hear what you think of the Biogon 35/2.0 and the NEX-7. Have fun shooting.
Hi Bjorn.
I have changed the filter to B+W MRC and it is working fine. Thank you once more.
After few days with Nex7 and Biogon 35mm f/2 I am very happy :
Compact, nice and light combo, Sharp images, Very convinient manual focusing.
Good luck
Glad that's worked out with the filter, Boris. Enjoy your new camera and lens and if you ever post some of your photos, I'd love to see them. Cheers