I prefer artificial light from electronic flash units rather than continuous light sources such as LEDs. That being said, when the working distance between lens and subject is small, a lens-mounted LED ring light makes sense to use.
Minimum focusing distance versus working distance
The “minimum focusing distance” is the distance from the subject to the focal plane. The “working distance” is the distance from the front of the lens to the subject. For macro photography, usually the latter is more important than the former.
According to Venus Optics (Laowa), the minimum focusing distance for the “Laowa 25mm f/2.8 2.5-5x Ultra Macro lens” is 23.4 cm at 2.5x magnification and 17.3 cm at 5x. According to several Web sites, the working distance is 45 mm (4.5 cm) at 2.5x and 40 mm (4.0 cm) at 5x, or a range of working distances from ~1.8 to ~1.6 inches.
Adding one or more extension tubes reduces the working distance and increases magnification. For example, adding a Kenko 12mm extension tube reduced the working distance from 45 mm to ~30 mm at 2.5x.
And it’s worth noting that adding the Laowa “Canon EF lens to Fujifilm X mount camera adapter” to the lens further reduces the working distance — the adapter is ~26 mm wide, essentially equivalent to adding a 26mm extension tube. Combined with the 1.5x crop factor of Fujifilm X-Series cameras such as the X-T1 and X-T3, it’s no wonder the magnification of the lens is increased dramatically when used with select Fujifilm cameras!
Ultra Macro Lens
The first two photos, courtesy B&H Photo, show the version of the Laowa lens for Canon EF. For what it’s worth, f/4 is the “sweet spot” for this lens.
Product image courtesy B&H Photo.
Look closely at the front of the lens. Notice a “flange” (one of two) that is visible around the outer rim of the lens. Those flanges are used to mount the Laowa LED ring light on the lens.
Product image courtesy B&H Photo.
LED Ring Light
The next two photos, courtesy Allen’s Camera, show the Laowa LED ring light.
Product image courtesy Allen’s Camera.
The LED ring light ships with a USB power cable. A power source for the ring light is NOT INCLUDED. My next blog post will feature a discussion of the pros/cons of the power source solution I decided to use.
Product image courtesy Allen’s Camera.
LED mounted on lens
The last photo shows the Laowa LED Ring Light mounted on the Laowa Ultra Macro Lens that is mounted on my Canon 5D Mark II digital camera. The USB power cable is connected to the LED ring light but not connected to a power source. (Don’t mind the clutter in the background!)
Notice the face of the LED ring light extends ~5 mm beyond the front of the lens, thereby reducing the working distance by ~5 mm (~0.5 cm). Plan accordingly.
Laowa LED and 25mm Ultra Macro lens mounted on Canon 5D Mark II.
Related Resources
- Have you ever wondered…? [a blog post by Walter Sanford (Hey, that’s me!) related to minimum focusing distance and working distance]
- Laowa 25mm f/2.8 2.5-5x Ultra-Macro – Review [lens-specific information regarding minimum focusing distance and working distance]
- Laowa 25mm f/2.8 2.5-5X Ultra Macro [Venus Optics (Laowa) Web site]
- Allen’s Camera [My first experience with Allen’s Camera was very positive. Rob, the sales associate with whom I spoke by telephone, was knowledgeable about the Laowa product line and very helpful.]
Copyright © 2020 Walter Sanford. All rights reserved.
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