[simons-photography]

thanks thats very useful

[Geekybiker]

4. extension tubes increase the distance between lens and film/sensor, reducing at the same time the distance between lens and object. They are an easy means to accomplish highly magnified macro shots. Their advantages are ease of use and a good rigidity. But increasing the lens-sensor distance also implies a considerable loss of light or better the illumination of the sensor will be reduced with the square of the increased distance. Double the distance between lens and sensor and the illumination will fall to a fourth!

Very good write up! Thanks.

Just one comment on 4- double the distance and you get 1/4th the light 2 stops just like a 2x TC.

So in terms of light TC and Extension tube seem to work identically?

[Canada_Rockies]

Very good write up! Thanks.

Just one comment on 4- double the distance and you get 1/4th the light 2 stops just like a 2x TC.

So in terms of light TC and Extension tube seem to work identically?

The extension tubes are focus range extenders. The teleconverter is an image multiplier. They are not directly comparable.

However, in your statement above, the answer is, "sometimes". If you put a 50mm extension tube on a 50mm lens, you will lose 2 stops, when the lens is focused at infinity (total extension is 100mm, lens node to film/sensor). You lose more still when you focus closer, because all the focus ring does is extend the lens even further. This is very noticeable when I put my 100mm macro on the front of my 50mm extension tube, then focus in to minimum focus.

[rvannatta]

The extension tubes are focus range extenders. The teleconverter is an image multiplier. They are not directly comparable.

However, in your statement above, the answer is, "sometimes". If you put a 50mm extension tube on a 50mm lens, you will lose 2 stops, when the lens is focused at infinity (total extension is 100mm, lens node to film/sensor). You lose more still when you focus closer, because all the focus ring does is extend the lens even further. This is very noticeable when I put my 100mm macro on the front of my 50mm extension tube, then focus in to minimum focus.

which is precisely the reason that a functional ring flash is so important to macro work. Wide open the depth of field is less than a fly's behind and if you are going to get an image at or near full stop down, you do need to turn on the light.

[Canada_Rockies]

which is precisely the reason that a functional ring flash is so important to macro work. Wide open the depth of field is less than a fly's behind and if you are going to get an image at or near full stop down, you do need to turn on the light.

Actually, I would prefer a flash that allowed only some of the sectors to light, on demand. Ring flash photos seem flat at times. I have never owned one, but the images I see are quite often very flat. Great for documentation of a flower or bug, but I prefer a bit of contrast in the image.