Road to Macro

Macro lenses come in all sorts of focal lengths. The most notable ones for full-frame tend to land around the 100mm or 105mm focal length (I'd even throw Tamron's 90mm in there since it's similar).

Nowadays, macro lenses come in all sorts of focal lengths and shapes. Some lenses offer a infinity focus, as well as good macro magnification, while a probe-type lens might be geared specifically for macro work, and may not offer utility outside of that.

On paper, a lens longer than 100mm may make for a better macro lens, since the longer focal length makes for higher magnification, but a lot of our longer vintage primes actually have poor close-up performance. That's when I thought:

What would it take to turn these lenses into proper macro lenses?

Here's a picture taken with my Sears 135mm (Pentax K mount) lens set to its closest focus distance:

In theory, we'd just need to add space between the lens and camera; we just don't know just how much space we need to add. As a baseline, we'll aim for a 1:1 reproduction ratio. We'll start with a DLX Stretch adapter, since it can improve close-focusing distance:

While it cuts down the 1.5m minimum focus distance down to 943mm, it's not nearly enough. I added a simple extension tube, as it's an affordable way to achieve some macro functionality. If the entire configuration is too long, we can always the segments.

Though apparently, that's a non-issue. Even with all of the section and components, we still have quite a bit to go. My next best option is a macro bellows. The base extension is less than the full bellows set, but at its longest length, it's nearly twice the added distance.

With full extension, we go a little past 1:1, which is good news, if you're looking to maximize your magnification. Definitely going to need a tripod for this setup, as hand-holding will net some shaky results at lower shutter speeds.

For the 1:1 ratio, I needed an extension of 152.47mm. With that much distance added, there's bound to be some light loss.

At the least amount of distance (the DLX stretch, fully retracted), a centered exposure is taken at f/2.8 and 1/30th of a second. With the setup at a 1:1 focus, the centered exposure is instead at f/2.8 and 1/4th of a second. This equates to three stops of light loss.

Is this a better way to get macro than a dedicated macro lens? Probably not. If the goal is to keep the setup as small as possible, then a lens designed for macro is your best bet. But if you have time to slow down or want to use some of your other lenses or don't want to shell out for a macro lens, this is a good way to bridge that gap.