Karl S writes on choosing a macro lens for high magnification photography:
I am a big fan of your site, thank you very much for your efforts. The reason for my email is to ask you a question about two of the lenses on your site.
I am interested in purchasing a 100mm macro lens for my Canon 5DMII to be used in my medical research in addition to my photography hobby. If I were purchasing the lens for my photo hobby, your website strongly suggests that I purchase the Zeiss 100 F2 Macro. As a former user of Leica M and Mamiya 7, I am naturally drawn to this manual focus old-school lens anyway.
The reason for emailing you is that I noticed the Zeiss has a magnification ratio of 1:2, whereas the Canon 100 2.8L has a magnification ratio of 1:1. The medical research project I am working on involves photographically counting microbubble ultrasound contrast agents. The ultrasound contrast agents consist of 1 to 5 micron sized microbubbles. These bubbles normally would require a microscope to visualize, let alone count (they are about half the size of a red blood cell), but they can be photographed with a 100 mm lens when illuminated by a laser, as they scatter light so efficiently that their illuminated size is larger than their actual size. That said, it would be optimal to use the entire area of my FF sensor to maximize resolution, and this is the reason I a looking for a magnification ratio of 1:1 or greater.
I have attached two images to this email. One of the images show a full-frame image of the cuvette containing echo contrast illuminated by a green laser, and the other image shows a digital zoom of the region of interest. These images were taken with a borrowed Canon 100 2.8L. Even with this lens, the laser illuminated region of interest is only about 1/6th of the entire frame at the minimum focal distance. Of course, the laser illuminated area would be even smaller with the Zeiss lens.
The solution seems to be the use of extension tubes, especially with the Zeiss lens. My questions for you are as follows:
1. Will the quality of the Zeiss (or Canon) lens be seriously degraded with the use of an extension tube?
2. B&H lists only one Canon extension tube in stock (or even available), the Extension Tube 25 II. B&H lists two other vendors that have a set of extension tubes that look like they have the necessary electrical contacts to allow for aperture adjustment (and autofocus with the Canon macro lens). One manufacturer is Dot Line" and the other is Kenko . The problem is the set of "Dot Line" extension tubes look incredibly cheaply made, and the B&H photo of the Kenko tubes do not show the electrical contacts. The question for you is how can I decide of the Canon Extension Tube 25II is the right size for my intended use? Would it be better to purchase the Dot Line or Kenko set of tubes? Do you have experience with any of these tubes? Is there another manufacturer of source of these tubes that would be better than B&H Photo?
DIGLLOYD: consider the Canon Macro Photo MP-E 65mm f/2.8 1-5x Manual Focus Lens for EOS, specifically optimized for your high magnification goal.
Extension tubes don't by themselves degrade image quality, but any time you go beyond the native range of a macro lens, optical quality is likely to degrade, because such lenses are optimized for particular magnifications. However, the degradation should be gradual and it’s only when moving well beyond the design range that one need be concerned, and with high magnification, many other challenges are likely to be more problematic (e.g. focus and lighting). Of more concern might be operational characteristics and any slop/wiggle in the connection of the extension tube to lens and camera.
The other issue is working distance and lighting, and Karl covers this well:
I pulled the manual for the Canon Macro Photo MP-E 65mm f/2.8 1-5x Manual Focus Lens off the Canon website, and indeed this lens looks like it is the best candidate for the job at hand.
As a personal note: I have a nice selection of Canon lenses, including TS-E, and I was looking forward to trying a Zeiss lens. I had waited a long long time for Zeiss to bring out a 35 1.4 for EOS, and over a year ago I gave up and purchased the Canon 35 1.4. I have to say that I have been very happy with this lens, but I am still sad that I missed the Zeiss.
As a side note, the focusing distance for 1:1 reproduction with a 65 mm lens will be shorter than for a 100 mm macro lens. Luckily, this lens does not appear to change the focusing distance too much as the magnification ratio is zoomed, but it is enough that a focusing rail will likely be needed. This results in two practical problems: (1) getting close enough, and (2) lighting the subject at the short focusing short distances, especially when shooting wide-open. In my case, the short working distance will be OK, as I need the whole apparatus to fit in a dark box, and also my subject is self illuminated with a laser, which is even better than an electronic ring flash. Thanks again for your help in this matter.
Don C comments:
For a greater working distance requirement I wouldn't rule out Canon's 180mm f/3.5 macro. I realize it's not your (Lloyd's) favorite lens, but I'm very happy with my copy and get good results with it.
I also have the Zeiss 100mm Makro-Planar - which is a sharper lens than the Canon 180mm - and the Kenko extension tubes. The Kenkos are full EF mount compatible and support pass-through for the electronics.
DIGLLOYD: absolutely, a longer focal length is helpful for working distance, but that is not a requirement in this case (indeed it could be a bulkiness problem), and the Canon 180/3.5L (about $1500) still only goes to 1:1. It’s a bulky and heavy lens that I never liked, nor was I was impressed with the samples I tried several years ago (two of them). The Canon MP-E 65mm f/2.8 is a better choice here because it’s designed expressly for the magnification involved.