Saturday, July 16, 2011

24TSE Mk I vs Mk II

I had always been happy with the Mk I lens on my cropped camera (30D)--okay maybe there was a bit of chromatic aberration (CA), but it was manageable--but I just wasn't happy with it on my 5D2. The Mk II version of the lens was reputed to be better, but my question was: is it enough better to justify the extra expense?

So, on a recent trip to the mountains, I borrowed a Canon 24 TSE Mk II to compare against my Mk I version on my full frame camera (5D Mk II). The weather on the trip ended up being less than wonderful, but I did get a chance to make a pair of test shots. The whole frame (reduced in size, of course) is shown below for both lenses (both on the 5D2). I have done nothing to the images beyond running them through RAW conversion in ACR 5.7. This includes a small amount of capture sharpening. But there is no further processing, and no output sharpening. CA was not addressed in any way.

The images below were taken with the camera horizontal, and the lens shifted upwards by 6 mm (on the scale on each lens). Yes, I know I cut off the top of the mountain--I did that so there would be some detail at the top of the frame.
Mk I

You can't see much in those web-sized images. So I'll show some 100% crops below. The first two are from near the top of the image--since the lens is shifted up, this means these are from near the edge of the lens' image circle.
Mk I

The next crops are from much lower down in the image--i.e., from closer to the middle of the image circle (recalling that the lens is shifted up).
Mk I
Mk I

For the images at the edge of the image circle, there is a world of difference, both in sharpness and in CA. The Mk II lens is most definitely improved over the Mk I! Near the middle of the image circle, however, there is almost no real-world difference in sharpness. The Mk II has essentially no CA in these images, while the Mk I has only a tiny amount.

Conclusion: For a 5D2 (or other full frame camera), the Mk II version of the lens is definitely superior. For a 1.6 crop camera, however, a Mk I version in the used market would be a very good value and most users would be happy with the results.

Other points:
1. The Mk II is noticeably larger and heavier (780 g vs. 570 g -- a 37% increase in weight).
2. The filter size is 82 mm on the Mk II as compared to 77 mm on the Mk II. I have other lenses with a 77 mm filter size, but none with 82 mm, so this means buying more (probably a circular polarizer and a ND filter) and also carrying them in the the field (even more weight).
3. The Mk II has the ability to adjust the tilt and shift planes independently of each other, while the Mk I had them 90° apart. (Okay, you could modify the Mk I so they were in the same plane, but this was not something for the faint of heart, and certainly not in the field.)
4. The Mk II has a lock lever to lock the lens at a tilt of 0°. Like the Mk II, there are still tightening knobs to "lock" the tilt and shift at any position, but the positive lock at 0° tilt is a welcome addition (speaking as one with lots of field experience with the Mk I lens).

The weight and increased filter size are a downside, but the overall quality is excellent. While I didn't test the lens with filters (I don't have any 82 mm filters), I strongly suspect that the larger filter size will reduce or eliminate vignetting when a filter is in place and the lens is fully shifted.

I still maintain that the Mk I version of the lens is very good on a 1.6 cropped camera. (Minor CA can be dealt with in processing.) But on a full frame camera, the Mk II is far superior, despite the extra weight and need for larger filters.


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