p.1 #1 · Can someone please explain extensiion tubes (searched but could not find appropriate info)
I would like to do a little macro photography but I would prefer not to invest in a new lens. I read somewhere that u could use an extension tube. I saw that B&H has two Kenko tubes for the canon camera. One is 12 and the other is 25. What exactly is the difference between these two? The B&H website says they magnify the same but the af will not work on the 12. Is this true? Is Kenko the brand to get?
p.1 #2 · Can someone please explain extensiion tubes (searched but could not find appropriate info)
The idea behind extension tubes is similar to that of a magnifying glass. As you move the magnifying glass farther from your subject, it appears larger and more magnified. The same is true with tubes. The farther you move the lens from the film/sensor, the larger the projected image (at the expense of loss of light).
Kenko tubes are popular because they're much cheaper than their Canon counterparts. Since there's no glass in them, and the extension tube passes the lens/camera pin connections straight through, there's nothing that would make the Kenko tubes "worse" than the official Canon ones.
p.1 #3 · Can someone please explain extensiion tubes (searched but could not find appropriate info)
I would go with a set of tubes so that you can change the magnification by changing the combination of the tube.
The other option is to use a macro filter such as Canon 500D. It should work with your 70-300IS well. In such case, you might want to get 77mm one and step down(up?) rings to attach your lens unless you have no plan on buying 77mm filter lens in the future...
p.1 #4 · Can someone please explain extensiion tubes (searched but could not find appropriate info)
Namflow wrote:
I saw that B&H has two Kenko tubes for the canon camera. One is 12 and the other is 25. The B&H website says they magnify the same but the af will not work on the 12.
Wrong and wrong. Where did you get this incorrect information? The B&H website clearly states:
"The Kenko Auto Extension Tube Set DG contains three tubes of different length - 12mm, 20mm, and 36mm - which can be used individually or in any combination to obtain the desired magnification. Actual magnification effect changes with each specific lens.
This DG Extension tube set has upgraded "Gate-Array IC" circuitry to work better with digital SLR's and some of the digital SLR lenses*.
Extension tubes are designed to enable a lens to focus closer than its normal set minimum focusing distance. Getting closer has the effect of magnifying your subject (making it appear larger in the viewfinder and in your pictures). They are exceptionally useful for macro photography, enabling you to convert almost any lens into a macro lens at a fraction of the cost while maintaining its original optical quality.
The extension tubes have no optics. They are mounted in between the camera body and lens to create more distance between the lens and film plane. By moving the lens father away from the film or CCD sensor in the camera, the lens is forced to focus much closer than normal. The greater the length of the extension tube, the closer the lens can focus.
When using the camera's TTL metering system, no exposure compensation will be required."
It says nothing about AF not working with one of the tubes because AF works with all of them, in any combination. When using them with a macro lens, you should be using manual focus, tripod, mirror lock-up, and cable release (or timer, or remote) anyway.
p.1 #6 · Can someone please explain extensiion tubes (searched but could not find appropriate info)
From the B&H website under 12mm Kenko Extension Tube Features:
"The Kenko 12mm UniplusTube DG (extension ring) is an accessory exclusively designed for use with standard AF lenses to shoot subjects at closer distance with higher magnification. Magnification ratio for TUBE 25 is about 1/2 with 50mm standard lens.
Provides perfect coupling with automatic aperture, TTL metering and AE mechanism. Does not support AF operation.
This DG Extension tube has upgraded "Gate-Array IC" circuitry to work better with digital SLRs and some of the digital SLR lenses. "
Notice the last sentence of the 2nd paragraph!!!!!!!
ALSO- look at last sentence of 1st paragraph. Now I will post what the website says about the 25 mm Kenko tube:
"The Kenko 25mm Uniplus Tube DG (extention ring) is an accessory exclusively designed for use with standard AF lenses to shoot subjects at closer distance with higher magnification. Magnification ratio for Uniplus Tube 25 is about 1/2 with 50mm standard lens.
Provides perfect coupling with automatic aperture, TTL metering and AE mechanism.
This DG Extension tube has upgraded "Gate-Array IC" circuitry to work better with digital SLR's and some of the digital SLR lenses.
"
I was not looking at the package of tubes as it was/is more than I want to spend.
To me, these paragraphs say the two different tubes have the same magnification of a 50 mm lens.
p.1 #7 · Can someone please explain extensiion tubes (searched but could not find appropriate info)
Namflow wrote:
From the B&H website under 12mm Kenko Extension Tube Features:
"The Kenko 12mm UniplusTube DG (extension ring) is an accessory exclusively designed for use with standard AF lenses to shoot subjects at closer distance with higher magnification. Magnification ratio for TUBE 25 is about 1/2 with 50mm standard lens.
[...]
To me, these paragraphs say the two different tubes have the same magnification of a 50 mm lens.
I think that should read 1/4 magnification with a 50mm lens.
mag = extension/focal length
12/50 = 0.24x
25/50 = 0.50x
50/50 = 1.0x
and here magnification means: "ratio of to a lifesize image on the sensor".
