Camera Labs

Quick test on the focus transition region... Canon 50mm f/1.8 II placed on tripod. Focus on text near its minimum focus distance. Repeat shots with Zeiss with tripod unmoved. Crops from middle of shot.



Canon at f/1.8, f/2.0, f/2.8, Zeiss at f/2.0, f/2.8.

Warning: I didn't get the focus exactly the same in these shots. It is slightly more forward on the Canon than Zeiss. Also ignore the white balance differences between the shots. The sun was playing hide and seek with the clouds during this shoot.

That makes it a bit harder to compare as you can't just look at the same part of each image between the two sets, but have to try and match up the focus zone manually. I think the LoCA of the Canon is less strong than the Zeiss, but the Zeiss has better sharpness in the focus region here. I'll have to re-do this under more stable lighting later to eliminate any contribution from white balance that might influence the subjective colour.

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Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.

AF accuracy next! Well, focus assist accuracy I guess is more correct.

On the 450D I did a test at around 39cm and 90cm according to the lens distance scale. On test shots, I was getting front focus of around 5mm and 15mm respectively. Time to get the 7D out to try the AF microadjust.

Repeating this it was possibly slightly worse on the 7D. Experimentally I settled on a setting of +16 for these test distances. There might be a very slight front focus remaining but its within the DoF now. For comparison, I used values of +3 on EF 35/2, +8 on 50/1.8 and +5 on 85/1.8.

The problem was at these distances, the DoF at f/2 is very thin, in the ball park of mm/cm as shown above which was perhaps around 50cm focus distance. Even tiny movements in the focus ring shifted the focus plane by a relatively large amount at that point.

This is not really much different from any other big aperture lens. If you do use them wide open, the wafer thin DoF is challenging to get absolutely spot on. With the adjustment on the 7D hopefully I can get a better hit rate manually.

Strangely enough, this error is less significant at very close focus distances, as it seems the error magnitude gets reduced along with DoF so they appear to converge. Now I just need to test it for more distant focus too.

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Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.

To wrap up the previous post on focus, the new AF micro adjust seems to work well at distances up to around 30m or so. It still front focuses beyond that. I note that for terrestrial viewing, the lens does seem to hit infinity accurately enough on its end stop. On the previous night star test, I did have to adjust the focus slightly to make point sources appear so.

Next up: astigmatism/coma. I find it hard to tell between the two and as they have a similar impact in the corners.



Canon 50mm f/1.8 II at f/1.8, f/2.0, Zeiss at f/2.0.

How's this for pixel peeping? I needed a point source approximation, and the easiest way I could make that was to make a black image apart from one white pixel lit up on my monitor. I then placed this approximately 10% away from the corner of the captured image. I adjusted the focus to make the captured point as small as possible. The Zeiss here does reduce to a small point, but the Canon I could not focus in such a way to make it go to a point. To one side, it looked like a line radiating from the centre (as shown) and if I put it the other way, it starts blurring perpendicularly to that. I think this fits the definition of astigmatism where it has varying tangential and saggital focal planes.

While this isn't a point I considered before ordering, it is useful to know as it makes the Zeiss more suitable for higher quality astrophotography than the Canon.

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Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.

I just done a more real world but still at home test between the lenses. I got the focus marginally out on one set at moderate distance with the Canon invalidating that comparison (just a few mm!) but another set closer up was ok. That set was taken near the MFD of the Canon and kept in same position for the Zeiss.

At f/2 to f/4 the Zeiss is noticeably sharper in centre regions. There was no subject at the borders for comparison. It was almost equal at f/5.6 but with a pixel peeping slight edge remaining to Zeiss, swapping over to Canon at f/8.

LoCA was about the same intensity on both, maybe fractionally worse on Zeiss but hard to tell. This is roughly in line with the earlier test.

Canon showed polygon bokeh shape already at f/2.8, the Zeiss doesn't until f/5.6 and even then less obviously so. Bokeh, excluding the shape, was about the same.

I couldn't see any significant difference in colour rendition.


With that, I think I can make a tentative conclusion. Where the focus range overlaps, there is no significant difference in image quality other than bokeh shape between the cheap Canon EF 50mm f/1.8 II and Zeiss 2/50 Makro-Planar as long as you don't pixel peep. If you do peep, you do find the differences but in the big picture they're going to be quite minor. The Canon does have a fractionally bigger aperture and AF. So as a general purpose 50mm prime, you can probably find better value elsewhere.

Of course, the Zeiss does have the ability to focus much closer giving more magnification, so there is nothing to compare with the Canon unless I break out extension tubes. This is an area I have yet to explore in detail.

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Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.

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Hmm. With the Zeiss costing about £1000 and the Canon costing under £100 you could buy the EF 50mm f/1.8 II and the EF 100mm f/2.8L Macro IS USM and still have plenty of change left over for a slap up family Christmas dinner. And when you took pictures of the turkey both Canon lenses could AF.

popo, you're not convincing me the Zeiss is particularly good value.

Bob.

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OM-D E-M5 + ED 12-50mm, H-PS14042E, H-F007014E, L-RS014150E, M.ZUIKO DIGITAL 45mm 1:1.8.
Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.

My need was a somewhat unique one. Having a Canon cheap prime trio (35/2, 50/1.8, 85/1.8) I did want something a bit nicer at 50mm in particular. As I also have the Sigma 150mm macro, I didn't need a full on macro, but I did want more close focusing capability than the regular 50mm primes, while maintaining the possibility of shallow DoF from big aperture.

The only other considerations in the similar ball park are the ancient 50mm f/2.5 compact macro which seems really unexciting and past it's "best before" date. The EF-S 60mm macro I'm not convinced is quite enough wide open, and pre-empts any future upgrade to full frame. Similarly there's the Tamron 60mm f/2 macro, but the focus ring on that also gets a pretty bad review.

I did think long about getting a regular 50mm prime which have their issues. The Sigma f/1.4 suffers from focus shift with aperture which is an instant deal breaker for me. Canon EF f/1.2 if memory serves me correctly uses focus by wire, which I can't stand even if I swallowed its even higher price, and it also has a focus shift. That only leaves the EF f/1.4 which is the closest to a viable alternative. That doesn't really focus close without external aids though.

So by process of elimination, the Zeiss is the only one to tick all my boxes. On the other side, while I always knew the 50mm f/1.8 II was a good lens for the price, I think we can upgrade it to being a good lens full stop (ignoring the plastic build and noisy AF anyway...)

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Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.

In a quick look today, I tried the Zeiss on the 1D to see what it looked like through that viewfinder. At that point, I wondered two things: what does it look like with the wider image circle, and secondly, how does it compare to the Canon if we increase its magnification to match?

Experimentally I had to put a 21mm extension tube on the Canon to get enough magnification, with focus on that set somewhere between MFD and infinity. Both apertures at f/2, I pointed it at my monitor with the point of focus in the middle of the frame. It was at a slight angle so the lower part of the frame was closer than the top.

The Zeiss returned what you would expect from an ideal lens. The in focus band running straight across the frame with edge sharpness comparable to the middle as far as the subject was concerned. Unfortunately the monitor pixels were quite a lot bigger than the sensor ones even on the low resolution 1D, so I can't talk about this in fine detail. The Canon was noticeably degraded in comparison. The middle was apparently sharp too, but the focus region formed a slight curve downwards (closer to camera) and at the edges it was very smeared.

I'll repeat this another time under more controlled conditions on the APS-C body, but this appears to be where the Zeiss earns its true value. Of course, I am operating the Canon outside of its intended operation region, so it is not a major surprise if it doesn't perform there. A fairer test might be one of the 50mm macro lenses, but no other will match the aperture of the Zeiss.

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Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.

Finally, have had a quick side by side look at macro performance. You could argue this is a bit of an unbalanced comparison, but it's what I have to had...

All lenses were set to give about 0.5x magnification. The Zeiss is assumed to be correct at MFD. I set the Canon I put on an extension tube and adjusted focus to approximately match the Zeiss. The Sigma 150mm I set to indicated 0.5x magnification on focus scale. 100% crops from camera jpeg.

Caution: the test setup had a window behind which might be contributing to the contrast reduction on the Canon and Sigma which don't have the "hood effect" of the Zeiss recessed front element construction. Samples taken near the image centre. Also to hold the target in place I stuck it in a DVD case, and the plastic film may have provided some unwanted reflection too.


Zeiss at f/2 and f/5.6



Canon at f/2 and f/5.6



Sigma at f/2.8 and f/5.6

What I don't show here is the corner performance. The DoF is so thin I found it too difficult to get the image plane perfectly aligned. Even with that consideration, the Canon does behave worst characteristic here, where the image softens quickly going away from the centre.

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Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.

Tonight I pointed the Canon and Zeiss at Orion for a comparison on their performance, particularly where points of light are involved.

On each line, the first 3 images are on the Canon, last 3 are from the Zeiss. Stars are Alnilam, Betelgeuse and Rigel, which are middle of belt, top left and bottom right (as seen from Northern hemisphere).

All are 100% crops taken on the 7D. I fixed at 4 second exposure to minimise trailing. I varied ISO to keep exposure constant, with ISO200 at f/2.0. Manual focus on Alnilam to minimise the visible spot size.

f/1.8


f/2.0


f/2.8


f/4


f/5.6


Up to f/2, the Zeiss is clearly better as the Canon doesn't do well as soon as you go away from the middle of the image. From f/2.8 onwards they're pretty close, although the fewer straighter aperture blades of the Canon induces diffraction spikes more easily.

While I did test at higher apertures, the results are not interesting since it doesn't further improve the image and you're throwing away light in this application.

Although the performance at f/2 is much better on the Zeiss, it is still not a great setting for high level astrophotography as vignetting across the frame is still significant.

For context, this is the whole frame resized showing the positions for the Canon shot at f/2.0. As I was using a fixed tripod the stars did shift as I was taking the images.

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Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.