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the 92% compared with the 95%... (1 Viewer)

The ability to discriminate between levels of brightness (luminance) obviously depends on how bright it is to start with and the size of the areas compared. For instance using big bold paterns at high light levels on a professional 10-bit computer monitor it's apparently possible to detect differences as small as 0.1%. Of course simultaneous comparisons within a field of view are not what we are talking about here. We are asking whether it is possible to spot a 3% difference in transmission between binoculars.

I've mentioned before the little experiments I've done on myself and others masking objectives to reduce transmission. When conducted in a way to represent the way most people compare binoculars, no one I've tried could spot a 10% difference. Here's an even simpler test for those with a light meter and a dimmable room light. Get someone else to edge the brightness up or down while you look away (as you would while comparing binoculars), checks the meter reading, and note any difference you think you might see. Some might find the results surprising.

David,

I've done the same and concluded that I must be an absolutely terrible judge of brightness. :-C

Ed
 
Estimating the brightness of extended objects is difficult.
The following is for night observations, not daytime.

For estimating the brightness of comets visually one needs to list the following.

Method of estimating, there are three or four.
The type of telescope of which there are several.
The aperture of telescope or binocular or E for unaided eyes.
The magnification.
The focal ratio of the telescope, but not of binoculars.

The results are given to 0.1 magnitude although the typical spread is 1 to 2 magnitudes with different size optics. (2.5x to 6x).
The reason is primarily that the larger the telescope, the fainter the magnitude or total brightness the coma or head appears to be.
An empirical formula can be used to correct for aperture, but the raw results are usually given.

Frequently a magnitude 7.0 comet in binoculars, say 20x80, will be readily seen in a dark sky by unaided eyes as magnitude 5.5 or 5.7.
All manner of binoculars are used down to 2x opera glasses.
The observers are usually very experienced.
 
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