# What is mFT FoV?

Started Jan 27, 2013 | Questions thread
Re: practical measurement with 20mm
1

Anders W wrote:

Sure. But a I am already satisfied with 6.7% accuracy, and I would rather spend the time on figuring out the lighting for my next project, instead of figuring out how many inches I can fit in the frame to the first decimal.

Why did you do the exercise in the first place then? The error you made is sufficiently large to explain the entire discrepancy between the official specs and the value you found. And had the discrepancy been real, it would have been large enough to suggest that the official specs refer to the FoV before rather than after correction (which is not the case). So what was the point of your test as a response to gollywop?

In physical sciences a significant fraction of measurements and calculations is done approximately, rather than exactly. One continually weighs the expense of an accurate calculation vs. the practical advantage of the added accuracy. Gollywop said that the corrected image is significantly smaller than the uncorrected one. I got a quick, but approximate estimate of the AOV of the corrected image, and found it insignificant for my purposes (under 10%). At that point there was no reason for me to go on with a more accurate estimate.

If you wanted to help answer gollywop's question, which is what I thought you wanted, then your assessment of what is significant and not needs to be adapted accordingly. As I pointed out, the discrepancy you found (on incorrect grounds) is large enough to change the answer to the question gollywop raised. Consequently, it is significant rather than insignificant in that context.

To convincingly answer gollywop's question, you need better methods, such as those I pointed to and employed for the purpose of measuring the actual FoV of the 20/1.7. Furthermore, these methods are no more time-consuming or otherwise demanding than those you used.

If you were just playing around for your own purposes, with no serious intent to participate in the discussion between the rest of us, then forgive me for thinking differently.

Anders W's gear list:Anders W's gear list
Panasonic Lumix DMC-G1 Olympus OM-D E-M5 Olympus E-M1 Panasonic Lumix G Vario 14-45mm F3.5-5.6 ASPH OIS Panasonic Lumix G Vario 7-14mm F4 ASPH +28 more
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