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thomasc

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Posted Reply with quote  #1 

Would anyone be kind enough to share how the calculation for "Pixels per degree" on the NIMH ML dashboard (V2) is performed using the following inputs :

- Resolution 
- Diagonal size (cm)
- Viewing Distance (cm)

Thanks,
Thomas
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Jaewon

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Posted Reply with quote  #2 
See the get.PixelsPerDegree function in mlconfig.m
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thomasc

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Posted Reply with quote  #3 
Hi Jaewon,

Thanks for pointing me to the calculation in mlconfig.m.

Estimates from horizontal and vertical pixel distances using the same methodology in get.PixelsPerDegree give differing estimates of "Pixels per degree" (for x and y axes).

Is the diagonal pixel distance used instead of the horizontal and vertical pixel distances simply to yield a single estimate?

Thanks,
Thomas
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Jaewon

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Posted Reply with quote  #4 
It is something I inherited from the original ML, but I think it is a reasonable way to get the estimate.

If you want to be so obsessive about this, be my guest. But the difference between screen width and height is just one source of error. For example, the monitor screen is flat, not curved like a sphere, so technically you need to stretch out your stimuli when you present them on the periphery, to compensate the curvature difference. Also you don't poke the ruler through the subject's eye, so your viewing distance measure is not perfect either.
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thomasc

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Posted Reply with quote  #5 
Thank you Jaewon
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