Testing the limits of any lens we can grab is both fun and instructive. Sometimes beautiful unexpected discoveries can be made.
In the previous article, we did a fun experiment with ordinary magnifying glasses sold in stationery stores. By attaching a magnifying glass, the simplest structure that can be used as a lens in a camera, to the front of a bellows, we took pictures and examined the optical problem called “chromatic aberration”.
After a long pause, I would like to expand a little further on the same topic. I didn’t feel like closing the topic without asking, “If even an ordinary magnifying glass can take a photo, what kind of photo can the best quality magnifying glass I got take?”
The macro branch of photography is perhaps the field with the most optical diversity. I throw everything I can find in the name of photography into the drawer with the logic that I will use it somehow. When I think about what is included in the scope of quality magnifying glass, the first thing that comes to my mind is Raynox close up filters.
Raynoxes are not exactly a simple magnifying glass. They are a bit more complex. Instead of a single piece of glass, they have a layered structure. This means less optical distortion.
I would like to briefly remind you again being one of the people who praise these filters the most. One of the best ways to force a lens to focus closer is to attach a Raynox in front of it. Apart from being small, light and sharp, it’s a great attachment that doesn’t get in between the body and its communication with the lens because it’s attached to the front of the lens. Those who want to use aperture control or autofocus will have no problem with this. You can take a look at the link article on the use of Raynox for macro purposes.
There are 3 models that interest us: DCR-150, DCR-250 and MSN-202. Since I only have DCR-150 and DCR-250, we will conduct our tests with these two models.
The smaller member of the family, the dcr-150, is a relatively weak lens with 4.8 diopters. Its main purpose is to turn tele lenses into macro lenses. If we attach a more powerful Raynox to tele lenses, things get a bit complicated and difficult.
Considering the DCR-150 as a lens, let’s take a look at its optical metrics. The diopter formula is defined as 1000/f. Small diopter values correspond to high focal length, i.e. tele lenses. For 4.8, we find the focal length as 1000/4.8 = 208mm.
We will look at the diameter of the glass to measure the aperture. Raynox’s rear connection filter diameter is almost exactly the same as the diameter of the glass. So without using a ruler, we can say that the diameter is 43mm. We divide the focal length by the diameter to convert this to an aperture value. We get 208/43 = f4.8. The aperture coincidentally turned out to be the same as the diopter value, in fact the two formulas are not related.
Lensimiz 208mm f4.8 değerinde.
It would be a good idea to add an external diaphragm when connecting the Raynox to the bellows. Those who do not have a diaphragm should not worry, it is not necessary. But if you have one, we can get additional aperture adjustment by putting it right behind the lens. It is preferable to be able to set the ideal values according to the situation and to have full control.
The connection formula with my equipment looks like this.
Body + Sony-Pentax adapter + Pentax bellows + M42 adapter + M42 bellows + M42 reverse 49mm adapter + Reverse Raynox
In order to focus the DCR-150 at infinity, we need to set the sensor-lens distance to 208mm, i.e. open the bellows quite wide. We don’t measure this value, of course. We will play with the length of the bellows until we focus where we want. Not all bellows can be opened this much. You will need to use some extension tube with the bellows for small bellows. Because we will need even more than 208mm of aperture to focus on nearby objects.
On the first try I connected the Raynox straight in front of the bellows, so that the 43mm side is connected to the bellows…
The result… I mean, what can I say, it’s like dreaming! It’s a bit blurry and objects glow like ghosts. I wouldn’t want to use it like this. Closing the aperture helps a bit, but not enough. I need to try the lens reversed. It is also easier to mount it on the reverse lens adapter with the 49mm side facing the bellows.
Yeah, that’s it now. The sharpness is there. Soft bokeh. Then we need to continue shooting with a real model.
For those looking for a portrait lens around 200mm, the Raynox DCR-150 is a sharp alternative. I have to say that it is not easy to use. Because we open the bellows too much, it becomes a big and bulky piece of equipment. Your wrists may ache at the end of the day. Still, it’s quite fun.
Personally, 208mm is a bit too much for me. The wider-angle DCR-250 model seems to have more potential. Let’s move on to it right away.
The DCR-250 has served me well. It was the next upgrade after my first macro lens. Since then it has done amazing things in many different tasks. The areas where I use the DCR-250:
- As a closeup filter (this is the manufacture purpose)
- As a tube lens in infinity microscope lenses
- In relay lens systems to redirect the projection that has been scattered outside the lens
- As a “focal reducer” behind the lens
- And as a stand-alone portrait lens (the subject of this article)
We’re killing five birds with one stone for now. That’s good enough.
For the DCR-250, we start with measurements in the same way. The lens has a diopter value of 8. So the focal length is 1000/8 = 125mm. We measure the same diameter value for the aperture, 43mm. Substituting it in the formula, we find 125/43= f2.9.
The Raynox DCR-250 is a 125mm f2.9 lens. It looks like it will be a great portrait lens. Since I know that normal mounting will not give good results, I test it in the same way with reverse mounting.
The details look very good. Let’s take a closer look at 100% magnification:
As I guessed at the beginning, the DCR-250 is better suited to this task than the other model. Since it corresponds to 125mm as a lens, it is not necessary to open the bellows too much. It can also be used easily with small bellows.
I didn’t mention the external diaphragm at all. So how does aperture play a role in depth of field and sharpness? Does it work?
Note: Yes the cat has a problem with one eye, unfortunately it is a nerve damage that will not heal. And yes, the photo above shows the same cat before the accident. That is an older photo.
The effect of the diaphragm is very obvious. I tested it at 4 different stops and it changes with a smooth transition as you rotate the aperture. We don’t know its value. In the upper left corner, a very soft bokeh and a narrow focus is obtained with the aperture wide open. The bottom right corner is with the aperture turned all the way down. Almost everything is sharp, but the sharpness is significantly reduced. In the last photo, the diameter of the aperture hole is around 1mm. In other words, although we don’t know the number, we get an exaggeratedly high aperture value when we turn it all the way down.
After the tests were completed, I continued to enjoy my new lens and used it a lot.
I can say that it is a very suitable lens especially for portraiture. When used without a diaphragm, it provides a sharp center but a soft effect towards the corners, drawing attention to the center. This situation, which used to be seen as a lens defect, adds movement and creates fun. It is really pleasant to use.
The Raynox DCR-250 is one of my lenses of choice when I’m looking for some cool portraiture.