Macro photography is the taking of images representing the subject in larger than life size. There are specific lens made for this that have at 1:1 or better magnification factor (the subject appears the same size on the sensor as it does in real life) these are the best solution but when starting off there are much easier ways to start. Depending on what you are shooting macro photography can be one of the easiest discipline in photography to do at a moments notice. You don’t need to get someone to model or help, you can build a tiny studio on a table somewhere and store it away easily, if you are shooting indoors its weather and time of day independent so its very easy to start and stop. The only possible issue is getting interesting subjects to shoot, flowers are great and easy to obtain, I find insects the most interesting but for better or worse Ireland does not have that many interesting insects.
There are a few factors that dictate the magnification factor of a given lens, its ability to bend light (focal length) and it minimum focusing distance as the two most important things. Of these the easiest thing to change is the focusing distance, if we can focus on the subject closer it will be larger on the sensor and we will get a bigger image of the subject. There are a few ways you can do this – you can use a close up filter which is a secondary lens that screws into the filter thread of a lens or you can use an extension tube to move the lens further from the sensor to achieve the same effect.
Of these options I prefer the extension tube because its basically an empty space while the close up filter is an actual optic element that can introduce its own problems. You can also use the same extension tube on all your lenses but since a close up filter needs to match the filter size of a given lens. The great thing about the extension tubes is that they are cheap being mostly plastic and an empty space.
Extension Tube Example
The example I’ll work through will use the Canon 18-55mm USM Kit Lens @55mm and f8. I also used a LED light ring because this was done in a dark room with the camera blocking the main light but you don’t really need this. The extension tube I was using was a Neewer set that has a 13mm, 21mm, 31mm tubes that can all be stacked too, it was similar to this one but had plastic threads. I did this by focusing on card using auto focus as close as possible then switching to MF and focusing closer positioning the camera until the card was in focus. Once done I left the focus as is and used that setting for all other shots because AF doesn’t really do well at macro distances even on dedicated macro lens and extension tubes make this worse.
No Extension Tube (~0.7x magnification)
Various Different Extension Tubes
The Downsides of Macro
When taking macro images – you need to pay a lot of attention to depth of field. Just like normal photography depth of field is the effect that blurs the background, its based on the distance of the subject from the lens and the aperture. The closer the subject is to the lens and the wider the aperture the narrower the depth of field. Since we have our subject very close to our lens (the example of above with all 3 tubes combined was practically touching the front of the lens) our focus plane (the area of the image in focus) is razor thin.
To illustrate this check out the following images, I must have bumped the zoom ring when taking the above because the following images were taken at 38mm rather than 55mm but they are good enough to show the DOF effect
There are also other differences on ISO etc but the thing to focus on is the amount of the image in focus. You can see from the above just how thin the focus plane is, its less than a cm @ f5.
When taking images like this you need to keep in mind that while really high f numbers will give you better depth of field they also introduce softness due to diffraction so while more of the image is in focus you give up sharpness throughout the image. You also start to run into ISO issues here too as the amount of light entering the lens @ f32 is tiny especially because the lens has a tendency to shadow the subject because its so close to it so you need to increase ISO and shutter speed to compensate. This can really impact final quality especially is your subject can move faster than a SD card. There are ways to deal with this which I will cover in another post.