Extension tubes and supplementary lenses - Photography course - Lesson 10

Photo by JD Hancock
This article is part of the online digital photography course.

These accessories are used for macrophotography, usually they are used by novice amateur photographers that have a limited budget, a macro lens is usually pretty expensive, therefore it’s right to explore this genre trying to spend the less we can with remarkable results before deciding if it is going to be the genre we want to perform or not.

Let's begin talking about supplementary lenses, they are mounted on the reflex lens to raise the magnification factor, while for compact cameras you need to buy a ring adapter.

You can combine together more lenses to increase more the magnifying capacity, but you have to pay attention and mount first the lenses with the higher rating.

If you don't want to mount more lenses the best choice would be a single lens with an higher capacity.

Supplementary lenses have usually 2 advantages:
  • They don't absorb light
  • They make the object appear closer.
Unlike supplementary lenses, the extension tubes raise the enlargement of the object and lower the minimum focusing distance increasing the space between the lens and the sensor (they have to be placed between the lens and the body of the camera), they are without lenses and are sold in sets of three pieces of different length, using longer tubes or combining more elements together the amount of light that hit the sensor decrease.

Extension tubes are provided of electric contacts that allows the reflex and the lens to communicate in order to keep the automatisms of exposure and autofocus.

Photo by Pascal
Disadvantages of extension tubes:
  1. To mount them you need to disassemble the lens exposing the sensor to dust.
  2. The brightness decreases of about 1 or 2 stops.
  3. The focusing will be harder because in the viewfinder the scene will be darker.
While summarizing the supplementary lenses they present these advantages:
  1. They are cheaper than extension tubes.
  2. They don't reduce brightness.
Photo by Guy Sie

Pay attention, supplementary lenses must be of a good quality or you'll experience aberrations that will influence the image quality. Aberrations increase with the increase of diopters and add up mounting more lenses together.

The best lenses are made of achromatic doublet stick together.

Between +1 and +3 they may work fine also with single lens cause of the minor aberration but with a +4 it's easy for a chromatic aberration to show up.

Translation by Nina Kozul

1 comment:

Rachel D. said...

Perfect time: I just bought macro lenses and enjoying macrophotography !
Cheers Marco