What is It?
The Laowa 25mm f/2.8 is a unique lens, so hang on, this is going to be a bit of a wild ride.
Most macro lenses are typically 1:1, meaning that they capture things at life size. The Laowa breaks well beyond that right from the get go: it’s a 2.5:1 to 5:1 lens. It doesn’t focus, it “macros.” By that I mean that there is one ring on the lens, and it simply changes the magnification ratio (marked at 2.5, 3, 3.5, 4, 4.5, and 5:1). Focus itself is at a fixed distance that varies with magnification. Note also that as you magnify, the lens gets longer.
And while the lens is marked as 25mm, that’s a little deceiving, too, as the angle of view it takes in is not 82° diagonally, but about 10° when looked at from the image sensor! Coverage is for the full FX sensor.
Yes, things are all starting to get confusing, so let’s back up a bit.
In terms of construction, we have a metal lens barrel that tapers to the front (front smaller than rear). At the very front is an aperture ring with click stops from f/2.8 to f/16 using an 8-blade diaphragm. There is no filter ring on the front. Inside the lens are 8 elements in 6 groups. One element is low dispersion. Length of the lens unextended is 4.5” (114mm), fully extended to 5:1 it’s 6.5“ (165mm). Weight is 14.1 ounces (400g).
When the lens is at 2.5:1 the focus point (fixed, remember?) is just under 9.2" (234mm). At 5:1, it’s 6.8” (173mm). But remember, that’s from the sensor. Working distance (front of lens to subject) varies as you magnify and is about 2” at 2.5:1, while at 5:1 it’s maybe an inch. Can you stack images with this lens to get deeper focus? No, because it has a fixed focus at any given magnification. If you change the magnification, you can’t stack the images together. You'd have to use a focus rail, very carefully, to do focus stacking with this lens.
The Laowa 25mm f/2.8 is made in China and retails for US$399. Besides the Z-mount version, you can find versions in the EF, RF, F, E, L, and K mounts. Laowa sells an optional tripod collar and front LED ring light for the lens.
Source of lens: purchased
How’s it Handle?
This lens handles you, you don’t handle it.
Hand-holding is next to impossible. Here are a couple of attempts at that:
You may be saying, oh Thom, don’t use f/2.8! Nope, I’m not doing that. I’m at f/11 or f/16 in these examples. Which should start to tell you just how ridiculously close you are to your subjects and how thin your depth of field is going to be. We’re talking about the bottom end of the microscope range with this lens used at its extreme.
How’s it Perform?
I can’t give you my usual information here, as I don’t have charts and subjects that will allow me to fully flesh out test values for this lens. Moreover, even the tiniest bit of camera motion would be influencing such numbers if I could capture them accurately. 5:1 is a little less contrasty than 2.5:1, that much I can see and measure.
I’ll say that the lens seems reasonably and consistently sharp, from center to edge (not quite into the corners). I see a very small amount of astigmatism. Laowa’s MTF charts seem to suggest that, as well. You’re actually going to struggle to get everything this lens can deliver in terms of detail. You need a rock steady tripod and you need to remove all motion from the camera (shutter slap, etc.). When you do, the results look very, very good.
Vignetting is surprisingly low, and linear distortion is too low for me to measure. It’s nearly impossible to discern longitudinal chromatic aberration because the depth of field is so thin at f/2.8, but I do see some, I think. Likewise, lateral chromatic aberration seems reasonably under control, though I could provoke a tiny bit at wide apertures.
Frankly, though, focus blur (and diffraction) are going to be the things you fight the most, as at f/2.8 and high contrast subjects, the focus blur will spill over edges.
This lens works best with flat (and small!) subjects while using a focus rail, but with patience, you can make it work for three-dimensional objects.
Final Words
This is a specialty lens, obviously. If you think about it, 5:1 on a full frame camera means your subject is 36/5, or about 7mm across. Even at 2.5:1 your subject is only about 14mm across. In other words, a quarter of an inch to a half inch!
So basically this is a lens for taking photos of small things at close distances. There's certainly a need for such lenses, but it's a specialty need, and you're going to need to be very patient with this lens. When I was testing this lens I was away from the office and didn't have access to a focus rail, which would have been immensely useful.
The lens seems very well made and it produces really nice results when you can get the focus plane where you want it and the subject lit. I won't go so far as to recommend it, as it really is a specialty lens, but if you have the need, patience, and the discipline, I'd very much say this is a lens that should be in your macro arsenal.
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