Light throughput equation (2 Viewers)

[kimmik]

7x and 8x chart. Binos towards the top left have better global brightness for weight, FL 7x42 and HG 8x42 are the best.

Binos towards the bottom right have worse global brightness for weight, but possibly better contrast depending on how it was optimised. e.g. all Leicas.

Center brightness is just transmission and exit pupil size - no need to use this chart for that.

One thing I've noticed already, is that SF 42 and SFL 40 are equally "top left", SF 32 and VP are equally midway, and Conquests are equally "bottom right", a clue to the Zeiss design and pricing strategy.

Graph deleted.

 

[james holdsworth]

HT 8x42?

 

[kimmik]

HT 8x42?

graph updated. its next to slc.

 

[kimmik]

Throughput vs weight predicts new intermediate Zeiss models almost perfectly. SFL 8x30 will be about 144m FOV.

Graph deleted.

 

[tenex]

One thing I've noticed already, is that SF 42 and SFL 40 are equally "top left", SF 32 and VP are equally midway, and Conquests are equally "bottom right", a clue to the Zeiss design and pricing strategy.

SF 42 and SF 32 have different "design/pricing strategies"?

If the same glass was put in a plastic housing it would be a more impressive performer?

Throughput vs weight predicts new intermediate Zeiss models almost perfectly.

Actually weight alone seems to predict the new SFLs.

It seems odd that "throughput" would correlate so tightly with weight; I'd expect more scatter here. Do parameters like vignetting need to be measured more carefully, or is everyone really using such similar designs and materials that lesser brands would need to be included to see more variation?

 

[henry link]

Do parameters like vignetting need to be measured more carefully...?

Yes.

 

[kimmik]

But did weight alone predict the FOV? The graph makes the chosen FOV obvious. I suspect the point of the graph was not understood.

All Zeiss data points assume the same vignetting so it is moot for the last plot.

 

[kimmik]

This plot removed transmission and vignette factors, and just looks at FOV and aperture.

Curio and NL 8x42 are clear outliers from the baseline trend.

 

[kimmik]

Here's a fun one - Curio sits exactly half way in throughput between its two competitors, but closer in weight to the UV. At 250g, it has nearly as much throughput as the 350g CL 8x25!

 

[tenex]

But did weight alone predict the FOV? The graph makes the chosen FOV obvious. I suspect the point of the graph was not understood.

I am starting to think I see what I think you mean, but "predict" is an interesting word that connotes causality. Patterns alone are interesting to observe and fun to play with, but you seem to be suggesting that there's a reason why SFL 30 will have the FOV it will, involving this relationship that you've discovered between weight and "throughput"... whose validity is even confirmed by the appearance now of SFL 30 with FOV corresponding (via "throughput") to its weight, just as you propose. Let's spell out what the line on your graph is supposed to say then:

"Modern binoculars are designed to deliver throughput (perceived brightness as defined above, principally in terms of FOV) proportional to their weight."

Yet SFLs are intended to be unusually light, and weight has nothing directly to do with optical performance (only to the extent of correlating with aperture), and FOV is primarily a function of magnification that otherwise doesn't vary much in modern binoculars until SF/NL, which are obviously another departure from traditional design... in fact they should outperform in throughput, so it seems quite strange on your graph that most NL models do not, and that EL 10x50 and SLC 10x56 also look like underperformers, despite striking most people as very bright -- and we are talking about your low-light equation for throughput here, which is curious because ordinary models not specifically designed for low light levels wouldn't necessarily be expected to follow the same pattern as large-objective models that are. So I'm interested, but still a long way from clarity here.

 

[kimmik]

A lot of good points, i will need to split up my responses.

Most immediately would like to point out that 10x always have lower throughput than 8x for the same weight. This is fundamental.

I didn’t have a easy way of drawing a separate trendline for 10x models so just imagine one by looking at the data.

 

[kimmik]

"Modern binoculars are designed to deliver throughput (perceived brightness as defined above, principally in terms of FOV) proportional to their weight."

Yes and because throughput per weight metric is a major determinant of desirability. Thats why SFL40 is so successful, same throughput per weight (even slightly higher) as the SF42, at a lower price.

The market research determines what specification is needed to remain alpha, and the optics are designed to this.

It is my analysis that throughput as I have calculated, is a major unadvertised determinant of desirability for binoculars. All else equal including weight and image quality, a higher throughput model will command higher price.

So in order to not harm sales of SF32 and VP25, the SFL30 needs not only to weigh in between, but also have throughput in between. Working backwards from throughput gives us the FOV as per previous post.

 

[kimmik]

Once you have mentally drawn the 10x trendline, the NL 10x42 will be placed better than it, but not by as big a margin as the NL 8x42 is from the 8x trendline.

The other way to look at this is that EL 10x50 and SLC 10x56 are already excellent.

 

[tenex]

OK, I didn't realize that was just the 8x trendline, and can now see a 10x one with shallower slope... but I'm still wondering why you're doing all this with the low-light throughput equation when that's not how binoculars are mainly used.

All else equal including weight and image quality, a higher throughput model will command higher price.

But aren't you contending that there won't be variation in throughput at a given weight?

 

[kimmik]

wondering why you're doing all this with the low-light throughput equation when that's not how binoculars are mainly used.

A few others including Henry have also previously said this, that large aperture/exit pupil isn’t just for the low light. It improves the image quality and eye placement. In my view there is no such thing as wasted aperture or wasted light - the more you have to work with the better. Heavier bigger is the penalty, so my graph precisely addresses this.

SFL40 is again an excellent example, it has such high throughput for weight that many 32mm buyers will get it even though the low light ability isn’t needed. Also 42mm buyers will also consider the downsize for the same reason. This is the slogan after all - SFL bright and light. SF brighter and heavier. Conquest less bright but heavier for toughness.

There should be a second graph of throughput vs volume, but it would take too much effort to collect the data haha. Would also be interesting.

 

[kimmik]

But aren't you contending that there won't be variation in throughput at a given weight?

Definitely a pattern is there. Baseline and standouts.

Conquest HD 10x42 is a standout better than other conquests.

Swaro NL42 and Curio are standouts out of all other swaro models.

 

[MiddleRiver]

Did I see a graph showing all 3 brands or did I dream that? I don't even see the SFL on graph now...?

 

[tenex]

wondering why you're doing all this with the low-light throughput equation when that's not how binoculars are mainly used.

A few others including Henry have also previously said this, that large aperture/exit pupil isn’t just for the low light. It improves the image quality and eye placement. In my view there is no such thing as wasted aperture or wasted light - the more you have to work with the better.

No, I agree with all that. The point of my question was that you had two different equations for throughput, daylight and twilight, and I wonder why you're using the latter for an overall perspective on design.

 

[kimmik]

Did I see a graph showing all 3 brands or did I dream that? I don't even see the SFL on graph now...?

Saving it for personal use for now, will post selected data points when needed .

two different equations for throughput, daylight and twilight, and I wonder why you're using the latter for an overall perspective on design.

A daylight version would be interesting too, I just don't trust the AFOV figures published by most brands. Swaro seems to publish true measured figures, so might do one shortly for interest.

The twilight data did show strong trends so went ahead and shared it here.

 

[kimmik]

Somewhat interesting too, that AFOV increases from 250g to 850g, then starts decreasing. Given enough money, there is no reason why the increase in AFOV can't continue. The SLC56 body can take a 75AFOV eyepiece with say eye relief of 16mm. Field curvature will need to be addressed.

NL 10x32 is the lightest one to achieve 70ish AFOV.

Habicht 7x42 is the lowest AFOV regardless of weight.

When eye pupil is smaller than exit pupil, and well aligned etc - higher the AFOV, brighter the image. (Higher the transmission brighter too, though all of the above are in the 90% or so range so FOV has the bigger influence).