Extension tubes or close up filters

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callumboath

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Callum
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Hi I was looking for a bit of advice. I am trying to get into macro photography and I am currently using close up filters on my Nikon 50mm f1.8 . I use a +10 normally and sometimes add a +4 as well. I shoot at at f18 to keep sharpness sometimes with pop up flash and seem to get reasonable results . Is it worthwhile investing in extension tubes? will they be more powerful magnification than what im using or focus from further away as sometimes i spook the insects I'm photographing as I'm only about 10cm away . I am looking at a set of auto ones with a 12mm ,20mm and 36mm for £56 Would I be better with these or stick with my filters as I cannot afford a macro lens at the moment. A couple of samples


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8 by urbexcallum, on Flickr

DSC_0090 by urbexcallum, on Flickr

DSC_0223 by urbexcallum, on Flickr
 
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I would recommend getting a raynox 150... the first shot has really bad CA and this is normally caused by those screw on close-up filters.

Extension tubes are fine too but can't fault the IQ on the raynox so that is what I'd personally go with.
 
Hi Callum!

My guess (and it is only a guess, I've never really played around with filters/achromats) is that extension tubes would reduce your working distance further, and probably wouldn't increase your magnification significantly, certainly on a 50mm lens. You may also have light loss to consider.

10cm seems a reasonable working distance to me. The best way to attack this issue is to improve your "field craft" otherwise known as "ninja skills" and your ability to approach subjects without spooking them. Move slowly, quietly and try to approach them from underneath rather than above. If they do fly off, wait a while (they may return to their favourite "perch" depending on the subject). Try getting up early and hunt them as they are just waking up and haven't warmed up fully.

If you still want to increase your working distance, the best way to do this is by increasing your focal distance. Try your filters on one of your larger lenses (if you have any), or the extension tubes may come in handy here. Failing this, then you probably need to look at getting a dedicated macro lens, but if you get your field craft up to scratch there should really be no need, even if you have to suffer through rather a large amount of frustration initially.

As a separate bit of advice, I would look to improve your lighting. This will have a huge impact on the level of detail and overall image quality, and be much more noticeable than changing how you achieve your magnification. Read up about macro flash diffusion, try some basic setups with your pop up flash (empty pringles tubes, spare polystyrene plates are a couple of examples of cheap construction materials that can deliver very effective results). Looking through your flickr page, you have some mixed results with your current setup. There are some very good ones (excellent in fact! The second image posted here is a good example), but others where the harsh lighting detracts. I can only imagine this is due to the changing ambient light, and you've "got lucky" in some cases. Understanding exactly what is going on here and finding the solution to control your lighting will be the quickest way to improve. You have everything you need to progress so you don't have to invest in any new kit at the moment.
 
Seeing Bryn and Tim's replies, I did a few measurements which I've documented in the tables below.

Notes on some terms used in the tables:
  • The "working distance" is the distance from the end of the lens (or filter if you are using one) to the subject.
  • "Achromats" are like closeup filters but are made from two or more pieces of glass so as to reduce chromatic aberration. The Raynox 150 mentioned by Bryn is an achromat. I use the Raynox 150 a lot, and also the more powerful Raynox 250 and the less powerful Canon 500D (a closeup lens, not a camera), both of which are also achromats. As well as achromats from Canon and Raynox, achromats from Marumi are quite popular I think.
  • All measurements are approximate, especially the smallest distances.
  • All magnifications are expressed in terms of Canon APS-C sensors, which are 22.5mm wide, so a scene of width 22.5mm is 1:1, a scene of width 45mm is 1:2 and a scene of width about 11.5mm is 2:1.
  • I don't own a 50mm lens, so I had to use my zoom lenses at around 50mm instead.
Extension tubes (see first table below) provide a lot of magnification with shorter focal length lenses, like your 50mm lens, but as Tim says the working distances get quite small. How much magnification you can get, and how small the working distance becomes, depends on how close the lens can focus.

For example, at 55mm focal length my 18-55 lens will focus at a working distance of 110mm. In contrast, at 55mm focal length my 55-250 lens has a minimum working distance of 680mm. This is why, as you can see from the first table, when used with extension tubes the 18-55 can achieve much higher magnifications at 55mm or so than the 55-250 at 55mm. The downside is that the working distances are much smaller.

Tim mentioned losing light. The "effective aperture" of the camera lens gets smaller when you use extension tubes, the more extension you use, the smaller the effective aperture gets (and the less light falls on the sensor). For example, using the 36mm tube may decrease the effective aperture by about a stop so if you set f/16 on the camera you will actually be using an ("effective") aperture of f/22. This means using a longer exposure or a higher ISO if using natural light, and it will also increase the loss of sharpness from diffraction.

Alternatively, you can decrease the aperture set on the camera. For example, if you want to use f/16 but are using 36mm of extension tube, you might set the aperture on the camera to f/11, and the 36mm extension tube will bring the actual ("effective") aperture back to f/16.

Achromats work best with longer focal length lenses. They work particularly well with telezoom lenses. I use my achromats with a 55-250 lens on my Canon 70D and as you can see from the second table you get a reasonable range of magnifications and quite manageable working distances, such as around 100mm working distances at around 2:1 magnification.

Achromats don't change the effective aperture and so they don't lose light and they don't increase the loss of sharpness from diffraction.


0689 01 Working distance and magnification with extension tubes on Canon 70D by gardenersassistant, on Flickr


0689 02 Working distance and magnification with achromats on Canon 70D by gardenersassistant, on Flickr


0689 03Minimum working distances on 70D by gardenersassistant, on Flickr
 
Thanks for that much appreciated
 
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