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Forum: Pentax SLR Lens Discussion
11-05-2017, 11:20 AM
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There are some tests they do using expensive equipment to test lenses. These lens tests however are flawed. It's on those lens testing protocols that these theories are based.
Given the tests are good for what they are good for but they are also not perfect and result in a lot of wrong ideas.
I'm not an engineer by any means but if I'm not mistaken they replicate a camera with a mount and sensor only that sensor is ultra sensitive and calibrated to measure rather than record light.
Then in a lab test they expose the same type of light of the same intensity across various lenses.
Naturally if you have a lens designed for a crop sensor in an absolute test it won't transmit as much light. This is because it's designed not to do that. The circle of light behind the lens is inherently by design smaller.
If you take scientific tests like that and publish absolute results it's going to show a difference.
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Forum: Pentax SLR Lens Discussion
11-05-2017, 10:40 AM
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These tests don't measure depth. They measure total volume.
Hence the flaw.
And the resulting 10,000 false teachings on the Internet.
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Forum: Pentax SLR Lens Discussion
11-05-2017, 10:15 AM
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Tony Northrup is full of crap.
Your lenses have f stops and t stops. F stops are a physical character of the lens. IE exactly how big is the aperture.
T stops measure how much light the lens can transmit from the front of it to the sensor. This is more a measure of efficiency of the design.
A full frame lens will transmit whatever amount of light that it is able to do.
The problem and mistake in his theory is that they are measuring at the sensor.
A smaller sensor will naturally record less light volume wise sheerly because of size.
A bigger sensor will naturally record more light because it's bigger.
There is a big flaw in his theory and methods.
If you put a 5 gallon bucket in your back yard and right next to it you put a kiddie swimming pool.
When it starts to rain which one will capture more rain? Naturally the kiddie pool will have a larger volume of water in it.
Tony Northrup on the other hand is asserting that this is because it it rained less over the top of the 5 gallon bucket.
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