More on extention tubes
Discussion
_dobbo_ said:
I guess I don't understand extension tubes, as I thought they were 2x or 3x, rather than 21mm 31mm etc.
I think you're thinking of teleconverters, which have a fixed effect on the lens they're used with. Extension tubes are different (no lenses) - by moving the lens further from the body, they allow macro photography but you can no longer focus on infinity.
Macro is about magnification, which is a combination of focal length and distance.
_dobbo_ said:
I guess I don't understand extension tubes, as I thought they were 2x or 3x, rather than 21mm 31mm etc.
What's the effective focal length you end up with here?
extention tubes do exactly that. they move the lens further way from teh camera which reduces minimum focus distance at a loss of infinity focus and DOF. they are sized by how far the move the camera out. better than clus up lenses because there is not glass involved
poah said:
better than clus up lenses because there is not glass involved
Good close-up lenses (and the best ones are expensive and have a couple of elements to them - Canon certainly used to make an L-series one) are better than extension tubes precisely because there is glass involved. When you put extension tubes on a lens you are going beyond the original specification of its optical design and sharpness or resolution will suffer. The exception obviously being dedicated macro lenses which are designed to perform best at close object distances.
Despite that, extension tubes are a good, cheap and very versatile way of getting a powerful close-up capability. I have an EOS-fit Jessops set and use them regularly. Because there is no glass in them I felt no compunction to buy the Canon ones, which are much more expensive and less versatile, although far better built.
SGirl said:
I just bought a set of extension tubes. They look lovely. But how do I light my shots with them on the camera?
Light? If you mean metering and your tubes don't couple the lens to the camera, I think you'll have to use Manual metering.
Modern cameras and lenses swap a lot of data between them and if you got manual tubes, that's all buggered, to use the technical term
>> Edited by simpo two on Thursday 9th March 15:49
SGirl said:
But - um... to put it in a less technical fashion: it's all dark when I peer into the viewfinder. How do I make it less dark? I tried setting the camera to manual mode, but it's still all dark in there.
Mode won't make any difference to what you see in the viewfinder; that's always at full aperture for viewing purposes. I don't know if extension tubes would make it a bit dimmer, possibly.
Does the front of your lens have the name of a camera maker emblazoned across it in silver letters? If so I have the answer
>> Edited by simpo two on Friday 10th March 08:43
simpo two said:
Mode won't make any difference to what you see in the viewfinder; that's always at full aperture for viewing purposes. I don't know if extension tubes would make it a bit dimmer, possibly.
Well, I tried taking a photo or two, and unless I have a strong light source shining on whatever it is I'm trying to capture, it all comes out dark. I set the thing to manual and everything. What would be good settings to start off with? Should I change the ISO and stuff as well?
simpo two said:
Does the front of your lens have the name of a camera maker emblazoned across it in silver letters? If so I have the answer
Hm, cute idea.
But no. I remembered that bit. Just setting it to Manual (manual exposure, not manual focus) will make things worse - you then need to adjust aperture and/or shutter speed manually until you get the exposure correct. Luckily with digital this is easy, it just takes a few goes.
>> Edited by simpo two on Friday 10th March 15:21
>> Edited by simpo two on Friday 10th March 15:21
SGirl,
If you really are as novice as you say you are then do the following.
Set the camera to P and take a photo of your given subject without the tubes, and make a mental note of the shutter speed and apature chosen to take the shot. Next put your tube/tubes on and set the camera to Manual, then set the shutter speed and apature to those from before. The tubes will cause you to need more light to make a correctly exposed image so choose to slow the shutter down or widen the apature and adjust the setting to suit...about 1/2 a stop per tube is a good starting point. Take the shot, check the histogram, and adjust again if necessary, and repeat untill you have a perfectly exposed image. You will get better at it the more you practice, so we expect to see lots of nice insect and flower photos in the very near future
If you're not a novice...I just wasted 5 minutes of my life
Martin.
If you really are as novice as you say you are then do the following.
Set the camera to P and take a photo of your given subject without the tubes, and make a mental note of the shutter speed and apature chosen to take the shot. Next put your tube/tubes on and set the camera to Manual, then set the shutter speed and apature to those from before. The tubes will cause you to need more light to make a correctly exposed image so choose to slow the shutter down or widen the apature and adjust the setting to suit...about 1/2 a stop per tube is a good starting point. Take the shot, check the histogram, and adjust again if necessary, and repeat untill you have a perfectly exposed image. You will get better at it the more you practice, so we expect to see lots of nice insect and flower photos in the very near future
If you're not a novice...I just wasted 5 minutes of my life
Martin.
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