Testing the limits of any lens we get our hands on is both fun and instructive. Sometimes you can stumble upon unexpectedly delightful discoveries.
In the previous review, we tried a fun experiment with ordinary magnifying glasses sold in stationery stores. We attached a magnifying glass—the simplest structure that can be used as a lens on a camera—to the front of a bellows and took photos, examining the optical issue known as “chromatic aberration.”
Let’s make a camera lens from a magnifying glass
After quite a long break, I want to take the same topic a bit further. I couldn’t bring myself to wrap things up without asking, “If even an ordinary magnifying glass can take pictures, what kind of photo would the best magnifying glass I own produce?”
Macro photography is perhaps the field with the greatest optical variety. With the mindset of “I’ll find a way to use it,” I toss anything I get my hands on for photography into a drawer. When I think about what counts as a quality magnifier, the first things that come to mind are Raynox close-up filters.
Strictly speaking, Raynox units aren’t simple magnifying glasses. Their construction is a bit more complex. Instead of a single piece of glass, they’re made of a layered design, which helps reduce optical aberrations.
As one of the loudest cheerleaders for these filters, let me remind you briefly. One of the best ways to force a lens to focus closer is to mount a Raynox on the front. Besides being small, light, and sharp, it attaches to the front of the lens rather than the back, so it doesn’t cut communication between the body and the lens. Anyone who wants aperture control or autofocus won’t run into issues. You can check out the post linked here for macro-specific use of the Raynox.
There are three models in our scope of interest: DCR-150, DCR-250, and MSN-202. Since I only have the DCR-150 and DCR-250 on hand, we’ll run our tests with these two.
Raynox DCR-150
The DCR-150, the smaller member of the family, is a relatively weak optic with a 4.8 diopter rating. Its main purpose is to turn telephoto lenses into macro lenses. If we mount a stronger Raynox on telephotos, things get a bit complicated and tougher.
Let’s think of the DCR-150 as a lens and look at its optical values. The diopter formula is defined as 1000/f. Small diopter values correspond to high focal lengths, i.e., telephotos. For 4.8, we find the focal length as 1000/4.8 = 208 mm.
For the aperture measurement we’ll look at the diameter of the glass. The Raynox’s rear mount filter diameter is almost exactly the same as the glass diameter. So without even using a ruler we can call it 43 mm. To convert this to an f-number, we divide focal length by diameter. We get 208/43 = f/4.8. The aperture happens to come out the same as the diopter value, though the two formulas aren’t actually related.
Our lens is 208 mm f/4.8.
When mounting the Raynox on a bellows, adding an external aperture is a good idea. Friends who don’t have an aperture, don’t worry—it’s not mandatory. But if you do have one, placing it right behind the lens gives you extra aperture control. Being able to dial in the ideal values and have full control depending on the situation is preferable.
With my gear, the connection formula works out like this.
Body + Sony-to-Pentax adapter + Pentax bellows + M42 adapter + M42 aperture + M42 reverse 49 mm adapter + Reversed Raynox
To focus the DCR-150 at infinity, we need to set the sensor-to-lens distance to 208 mm, which means opening the bellows quite a lot. Of course we don’t have to measure this. We’ll play with the bellows length until we can focus where we want. Not every bellows opens this far. With shorter bellows you’ll need to add some extension tubes, because to focus on nearer subjects you’ll need even more than 208 mm of extension.
In the first attempt I mounted the Raynox to the front of the bellows in its normal orientation—that is, with the 43 mm side attached to the bellows…
The result… well, how should I put it—it’s got a “dreamy” effect! A bit soft, with ghostly halos around subjects. I wouldn’t want to use it like this. Stopping down helps a little, but not enough. Time to try mounting the lens reversed. Mounting it on a reverse lens adapter with the 49 mm side facing the bellows is also easier to do.
Now we’re talking. Sharpness is on point. There’s a smooth bokeh. Time to continue the shoot with a real model.
For those looking for a portrait lens around 200 mm, the Raynox DCR-150 makes for a sharp alternative. That said, it isn’t exactly easy to use. Because we open the bellows so far, the setup becomes big and unwieldy. By day’s end, your wrists may ache. Still, it’s a lot of fun.
Personally, 208 mm feels a bit much to me. The wider-angle DCR-250 looks like it’ll have more potential. Let’s jump right to it.
Raynox DCR-250
The DCR-250 has served me well. After my first macro lens, this was the next add-on. Since then it’s pulled off surprising feats in very different areas. If I list the ways I’ve used the DCR-250:
- As a close-up filter (its intended use)
- As a tube lens for infinity-corrected microscope objectives
- In relay-lens systems to gather image spilling outside the lens
- As a “focal reducer” behind a lens
- And as a standalone portrait lens (the subject of this article)
For now, we’re killing five birds with one stone. More than enough.
For the DCR-250 we again start with measurements. The lens is rated at 8 diopters, so the focal length is 1000/8 = 125 mm. For the aperture we measure the same diameter, 43 mm. Plugging into the formula gives 125/43 = f/2.9.
As a lens, the Raynox DCR-250 comes out to 125 mm f/2.9. It looks like it’ll make a terrific portrait lens. Knowing that a normal mount wouldn’t give good results, I’m testing it reversed again.
The details look fantastic. Let’s zoom in at 100%:
As I suspected from the outset, the DCR-250 is better suited to this than the other model. Since it corresponds to 125 mm as a lens, you don’t need to extend the bellows as much. It can be used comfortably even with short bellows.
I haven’t mentioned the external aperture at all yet. So how does aperture affect depth of field and sharpness? Does it help?
Note: Yes, there’s an issue in the cat’s eye that looks completely black, and unfortunately it’s nerve damage that won’t heal. And yes, in the photo above you can see the same cat before the accident. That one is an older photo.
The effect of aperture is obvious. I tested four distinct steps. As you turn the aperture ring, it changes with a smooth transition. Without measuring we can’t name the exact values. At top-left, wide open, you get very creamy bokeh and a narrow plane of focus. Bottom-right is stopped all the way down. Nearly everything is in focus, but overall sharpness has dropped significantly. In the last photo the aperture opening is about 1 mm in diameter. So even without calculating the numbers, when you crank it all the way down you’re hitting an extremely small f-number.
After wrapping up the tests I kept enjoying my new lens and used it a ton.
I can say it’s especially well-suited for portraits. Without an aperture, having a sharp center but a gentle softening toward the edges pulls attention inward. What used to be considered a lens flaw adds motion and playfulness. It’s genuinely fun to use.
The Raynox DCR-250 has joined the list of lenses I can reach for when I want a slightly flashy portrait look.
