For aquarium macro photography, is internal focusing better than an extending-barrel macro lens?
Asked 3/10/2016
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I want to photograph fish through aquarium glass, so my usable distance is limited by the space between me and the tank plus the tank’s depth. I’m comparing macro lenses such as different Tamron 90mm versions, where one uses internal focusing and another extends while focusing. Even though both can reach 1:1 at about the same minimum focus distance, does internal focusing actually help in this situation, or should I be looking at something else like focal length and working distance?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
10y ago
2 Answers
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Keep in mind that the focus distance is measured from the sensor plane to the subject. The distance from the front of the lens to the subject is called the working distance. You might have two lenses with the same Minimum Focus Distance that have widely varying Working Distance.
The Tamron SP AF 90mm f/2.8 Di Macro Lens (Tamron lens ID 272) has a working distance of only about 3.6 inches.
The Tamron 90mm f/2.8 Di VC USD Macro Lens (Tamron lens ID F004) has a working distance of about 5 inches.
The Tamron 90mm f/2.8 Di VC USD Macro Lens (Tamron lens ID F017) has a working distance of about 5.5 inches.
The Tamron 180mm f/3.5 Di Macro Lens (Tamron lens ID B01) has a working distance of about 9.6 inches and might be better suited to your use case.
Also keep in mind that the refractive properties of the water in the aquarium and, to a lesser extent, the glass of the walls of the aquarium will affect focus distance, working distance, and maximum magnification. In this case the water should work to your advantage.
Originally by user15871. Source · Licensed CC BY-SA 4.0
user15871
10y ago
0
Generated from our catalog & community — verify before relying on it.
What matters most here is not whether the lens is internal-focusing by itself, but the lens’s working distance at the magnification you need. Minimum focus distance is measured from the sensor plane, while working distance is from the front of the lens to the subject. Two lenses can have similar minimum focus distances but very different usable space in front of the lens.
From the answers, the older Tamron 90mm macro has about 3.6 in working distance at 1:1, while newer 90mm versions are around 5 to 5.5 in. So yes, an IF design can help if it gives you more working distance, but IF is not automatically the main advantage. A longer focal length macro is often better for your use: for example, a 180mm macro was noted at about 9.6 in working distance.
Also, lenses with more focus breathing can change effective focal length at close focus, which may affect magnification and framing.
Bottom line: for shooting fish in a tank, prioritize working distance and focal length, not just whether the barrel extends.
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