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01-20-2014, 02:43 PM   #1
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Teleconverter Effects?

I understand that a teleconverter reduces the amount of light that makes it to the sensor: a 1.4x will reduce by 1 stop, a 2x will reduce by 2 stops. Thus, at a particular f setting, proper exposure requires 1/250 without the teleconverter, with a 1.4x the proper exposure will be 1/125 and with a 2x it will be 1/60.

My question is: what happens to the DoF? If I set the lens at f/2.8 and employ a 1.4x TC, does my DoF still look like it would at 2.8 or is it basically what it is at 4?

01-20-2014, 03:11 PM   #2
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You will effectively get F 4. That's why fast primes cost more. Kudos for using the teleconverter. It can turn a box of old lenses into a whole new adventure.
01-20-2014, 04:43 PM   #3
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QuoteOriginally posted by MadMathMind Quote
I understand that a teleconverter reduces the amount of light that makes it to the sensor: a 1.4x will reduce by 1 stop, a 2x will reduce by 2 stops. Thus, at a particular f setting, proper exposure requires 1/250 without the teleconverter, with a 1.4x the proper exposure will be 1/125 and with a 2x it will be 1/60.

My question is: what happens to the DoF? If I set the lens at f/2.8 and employ a 1.4x TC, does my DoF still look like it would at 2.8 or is it basically what it is at 4?

DOF is as if it was the longer focal length at the smaller aperture. DOF actually gets smaller.
01-20-2014, 04:51 PM   #4
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What happens with the DOF? Because your F stop increase, you can think that the DOF will increase to. But is not the case, because in the same time the focal lens is increasing to, and this has the result a decrease of DOF. What is must important?

Use a DOF calculator, and you will see that DOF decrease.

You can find such a calculator here:

Online Depth of Field Calculator

01-20-2014, 11:43 PM   #5
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Just remember that depth of field is a function of final image size. Using a 2x TC is the same as enlarging the image to twice the size. What was acceptably sharp in the native mode will be just as I sharp when doubling the size
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