Photographing Insects: Raynox DCR-250 vs. Extension Tubes
Comparing the Raynox close-up lens with extension tubes
There are two different ways in which you can increase the magnification of your lens: extension tubes and close-up lenses. Here I compare the two, using the popular Raynox DCR-250 as close-up lens.
An extended version of this article has appeared in my free book My Journey into Insect Photography that you can download here.
Extension tubes
Extension tubes are rings that you place between the lens and the camera body. They put the lens further away from the sensor, changing the focal length of the lens. You can get closer to your subjects and, as a result, the magnification increases.
So the main effect is that extension tubes decrease the minimal focus distance. However, they also decrease the maximal focus distance, so you can no longer focus on infinity. Extension tubes come in different sizes. The longer they are, the smaller the focus distance becomes and the higher the magnification. I combined two tubes from Meike, that together are 31 mm long.
The increase in magnification depends on the focal length of the lens. The smaller the focal length, the higher the magnification. See my previous article on extension tubes for details.
So to get the highest magnification with extension tubes, use a small focal length and focus as close as possible.
Close-up lenses
A close-up lens is a magnifying lens that you put in front of your lens. You can buy very cheap ones but those can have a rather negative effect on the image quality. So you are recommended to get a more expensive one that has higher quality. Here I use the popular Raynox DCR-250. It cost around 70 euro.
Close-up lenses work completely different from extension tubes. They work best when the focal length of the lens is large. So if you use a zoom lens, use maximal zoom for maximal magnification. Also, you should preferably focus on infinity (which is actually some 11 cm with my lens; see below).
So to get the highest magnification with close-up lenses, use a large focal length and focus as far away as possible.
The results
I did some extensive experiments. I used my Canon R7 APS-C camera together with the RF-S 18–150mm kit lens. Note that, because this is an APS-C camera, you automatically get an extra magnification factor!
In the following tables, I look at the maximal and minimal magnification you can get at different focal lengths of the camera. Let us first look at the lens without any tubes or close-up lens.
For each focal length the table show the minimal width in cm of the area you can photograph, the minimal focus distance from the lens, also called the working distance, at which this is obtained (in cm), and the corresponding magnification factor. Focal lengths smaller than 50 mm are not useful as the magnification factor goes down again.
As can be seen, the lens alone already achieves a very good magnification factor of 0.78 at a focal length of 50 mm. This is due to the APS-C sensor. With a full-frame sensor this would be close to 0.5, which is still rather good.
Now let us look at the effect of adding 31 mm of extension tubes.
As can be seen, you can now achieve a magnification factor of 1.38 at focal length 70 mm. For smaller focal lengths the distance to the subject become unworkable. Note though that this is achieved at a distance of 3 cm from the lens. For higher focal lengths the magnification goes down a bit, but the distance increases considerably, making it easier to approach the subjects.
I also include the maximal focus distance that is still possible, and the corresponding width of the area and the corresponding magnification factor. Note that the range in which you can focus is rather small for a low focal length (between 3 and 12 cm) but increases considerably for a larger focal length. This is useful. For example, when photographing butterflies I typically use a focal length of 150. You can stay far enough away from the insects, and the magnification is perfect for such a large insect.
Now let us look at the Raynox DCR-250. The effect is rather different.
As can be seen, the largest magnification of 1.89 is now achieves at 150 mm focal length, focusing as far away as possible. The distance from the lens to the subject is then 11 cm. As was expected, you better always focus as far away as possible. You get a comfortable distance to the subject of 11 cm and very good magnification.
However, notice that the focus range is very small, only between 7 and 11 cm at 150mm focal length. That requires some practice, in particular when shooting handheld. When you are not in that range the image very quickly gets too blurry to even find out where the insect is. This sometimes makes it really hard to locate the insect in the viewfinder.
All these numbers are nice, but the effect is easier to see with some images. In the following four images you see a flower at the maximal magnification you can achieve, with the lens at 50 mm without anything, with extension tubes at 70 mm, with the Raynox at 150 mm, and with both the tubes and the Raynox (see below).
You can clearly see the increased magnification and reduced depth of field.
Extensions tubes or close-up lens?
So how do they compare?
- Magnification. This is good for both of them. The Raynox gives a somewhat larger magnification. This could also be achieved by using some longer extension tubes.
- Minimal focus distance. For the Raynox, the minimal focus distance at high magnifications is considerably larger than for the extension tubes, which makes this the winner.
- Flexibility. The extension tubes, together with the zoom lens, give a lot of flexibility. You can go from a magnification of 0.35 all the way up to 1.38. So you can capture both large and small insects. For the Raynox, the range goes from 0.92 to 1.89, which means that it is impossible to photograph larger insects.
- Ease of use. You can easily add or remove the Raynox. It simply clicks on the lens. Removing extension tubes is more work, and you do not want to do that too often because you might get dust on your sensor.
- Price. Both are rather cheap. The extension tubes were 45 euro on Amazon and the Raynox DCR-250 was 70 euro. So tubes are cheaper (and there are even cheaper ones).
Of course, a very important other factor is image quality. I did not do extensive testing here, but other sites report similar image quality, with a possible slight advantage for the Raynox.
Combining them
What about using both extension tubes and the Raynox? You would expect an even better magnification. Here are the results.
You indeed get a somewhat better magnification factor of 2.12 at 150mm, with still a decent focus distance of 10 cm. But the difference with just using the Raynox is not very large and you loose a lot of flexibility.
There is however a use-case for this. If you want the flexibility of the extension tubes (larger range of magnification factors) but sometimes need a higher magnification, you can simply click on the Raynox and get the extra high magnification for a particular shot.
The following image of a plant bug of less than 1 cm shows the effect of combining extension tubes and the Raynox to get maximal magnification. Note the shallow depth of field though. Not using the Raynox and doing a digital crop would yield a similar image, but with a larger depth of field.
Longer lenses
What happens when you use a longer lens? To answer that question I tried extension tubes and the Raynox 250 on my Canon RF 100–400mm lens (again on the Canon R7 APS-C camera). Without tubes or Raynox, this lens achieves a magnification of 0.71 at 400mm, while the distance is still 77 cm.
For extension tubes the results are not very spectacular. That is to be expected as extension tubes work best with small focal lengths. But they can still be useful if you need to keep your distance to the insects. At 400mm, with the 31mm extension tubes, the magnification factor becomes 1.03 at 65 cm.
The effect for using the Raynox 250 though is quite amazing. I only checked at the maximal focus distance, as this is what you should use anyway. Here are the results.
As you can see, the magnification factor goes up to a whopping 5.14 while you are still at 11 cm distance from the subject. And combining it with extension tubes you can increase the magnification to 6. The depth of field at such a magnification though is extremely small so you must use a tripod, focus rail, and, most likely, focus stacking. Also, I have no idea what the image quality will be. I will check this out in a later article.
In the field
To test thing further, I took the equipment out to the field and tried to photograph some insects. I quickly noticed that just using the Raynox was not very useful when photographing handheld. Using extension tubes was considerably easier. But I did use the combination of the tubes and the Raynox.
Focusing handheld with the Raynox seems to be much harder than using extension tubes, also at the same magnification. This applied to manual focus but in particular to autofocus. I am not exactly sure why. It seems the depth of field is smaller with the Raynox (while focusing). Also, it might have to do with the fact that moving the camera to and from the subject has a different effect on the magnification. What was surprising was that using the Raynox together with the extension tubes seemed easier than just using the Raynox.
I normally use a flash and use TTL (with some flash exposure compensation). I noticed that with the Raynox this did not work very well. Images were regularly over-exposed. I could correct that with the flash exposure compensation, but this was not very consistent. Using just ambient light worked fine. I am not sure what causes this. I should experiment a bit more with manual flash settings. (I did already set the flash zoom to manual, so that cannot be the issue.)
Conclusions
So should you use extension tubes or the Raynox? I think the Raynox is great if you incidentally need more magnification. It is easy and fast to click on the lens, and you are ready to go. For continuous extra magnification, use extension tubes. Here are some use cases:
Macro lens. If you have a good macro lens, using extension tubes does not make much sense. The Raynox though helps to get an extra push in magnification when needed.
Normal lens for macro. If you use a normal (zoom) lens, I recommend to use extension tubes if you go out to shoot insects or macro. You can still incidentally combine it with the Raynox for extra magnification when required.
Casual photography. If you are shooting all sorts of stuff (not just macro) but want to do occasional macro shots, extension tubes are a hassle. In this case the Raynox can be handy.
Controlled environment. If you photograph insects in a controlled environment, like indoors, with a tripod and possibly a focus rail, you can use a long lens with the Raynox to get maximal magnification.
So will I continue using the Raynox? Yes, but as an addition to using extension tubes, until I get myself a true macro lens, in which case I might drop the tubes.
Next: Lessons Learned
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Mark Overmars is a dedicated insect photographer that loves to share and regularly publishes about his work and about photography in general. You can visit his website at www.insectphotography.org. Download his free insect photography book at www.insectphotography.org/book.
