ZEISS SF and HT in latest Norwegian test10x (1 Viewer)

Chosun Juan said:

David (Typo) has said before that the Zeiss "explanation" of maximizing "coarse" contrast at the expense of fine detail resolution in the x54 is baffling, and I agree -- it just doesn't ring true. Never in my life have I ever seen an MTF (Modular Transfer Function) chart where the coarse contrast curve lies above the fine resolution curve. Never!

Click to expand...

Chosun,

I'm not that familiar with camera lens MTFs but some reviewers at least draw a distinction between contrast at 60 cycles per degree and 20 cycles per degree to approximate to categorise high resolution and 'sharpness'. A high 60cpd value will be high resolution. A lens with a low 60cpd value but high 20cpd value will be sharp. This is based on certain presumptions about the size and viewing distance of the resulting print. It is often complicated by these relative values changing with f-number.

There is the potential for binocular designers to manipulate performance in the same way. It's unclear to me if they do deliberately, but it is evident that differences do exist all the same.

Most binocular users will have an optimum acuity between 30 and 60 cycles per degree when the light is sufficient to contract their pupils to about 2.5mm. A perfect optic would deliver around 75cpd at the corresponding objective diameter for an 8x. In fact many better binoculars are between 60 and 75cpd. However, visually we perceive optimal 'sharpness' between 6 and 10 cpd. A binocular with poor resolution but high contrast at 6 to 10cpd would appear 'sharper' even though it was lacking in detail. At the time I reckoned the HT 8x54 would have an effective resolution value for a 20mm stopped down objective of about 9 arcseconds which would be about 50cpd or more typical of sub-£200 models. I think the Swaro CL is worse still.

The DIN ISO shandard prevents the big names from making a binocular that is really really tuned for 'sharpness' alone, but it's clear there are contrast differences in the 6 to 60cpd regions which can alter perceptions of effective resolution and 'sharpness'.

David

henry link said:

I guess I'm going to have to introduce a contrarian view about contrast. I can't think of any mechanism that could cause visual optics to have too much contrast <snip>. Even the highest contrast binoculars never have contrast equal to the scene being viewed because aberrations and light scattering in the optics always transfer some photons from the bright areas where they are supposed to be into the dark areas, where they become a thin fog of non image forming light.

Click to expand...

I totally agree. You can't have too much contrast, and high contrast requires, as I see it, high transmission (the higher the better), a flat transmission curve and excellent baffling to get rid of as much stray light as possible. "Too much contrast" makes no sense at all.

And if people are complaining that one particular binocular is "too bright", they need to put on sunglasses in bright conditions. Or ask the manufacturers to provide filter threads and appropriate filters. In some conditions, for instance on sunny days on snowy ground in the mountains, such filters would be very useful ideed. Some of the older binoculars, for instance the Russian ones, were provided with strong yellow filters for such situations.

Hermann

I'll also chime in with agreement. I cannot think of any ways of reducing contrast in binoculars or telescopes from "too much" to "just right" that would not compromise the image in serious ways, and that assuming that there would be a level of contrast that was lower than maximum and also better for the human eye somehow.

Also, if there was a wish by the manufacturer to tweak the optical formula in a way that would increase lower frequency MTF by reducing high-frequency MTF, such fine-tuning would be lost in actual manufactured copies since manufacturing tolerances are not high enough.

Perceived contrast I believe is influenced to a significant degree by the transmission characteristics and stray light control of binoculars, as stated by many here, and will also vary depending on what exactly you are looking at. This leads to subtle differences between models in the ease of detecting some color hues under some circumstances, but because of the number of variables involved, it is difficult to make blanket statements about this.

Another factor significantly influencing contrast, both real and perceived, in binoculars is the cumulative optical flaws or aberrations in a particular binocular sample. This I have seen when having the opportunity to test and view with a number of identical binoculars. The units with the lowest overall aberrations have a markedly better contrast and "snap" to the image than the ones that have high aberrations.

Kimmo

It seems pretty clear that my idea about too much contrast leading to merging of dark colours is wrong and I must return to my original theory that the effect I see is caused by differing colour transmissions.

Thanks to everyone who has contributed to this discussion and my education.

Lee

Troubador said:

LOL. You may not have meant this but your sarcasm steed is certainly not trusty. :-O

No I haven't read the article yet but I will certainly do this. In fact I might do it today if the present gale and lashing rain doesn't ease off.

Troubadoris hates carrying and handling 42s so we will give it a go with us both using the little Terras which BTW are fun. There are super low tides over the next few days so we will be indulging in precarious rock and seaweed clambering and the Terra 32s will be our choice for this from now onward so we don't risk our pricier instruments.

If the strike rate of otter spotting and other stuff remains the same then I shall have to admit its not down to the bins but to other factors, most likely eye/brain related.

Leo

Click to expand...

Well Friends

Following our recent weeks on Ardnamurchan I can reveal that my theory about Zeiss colour-tone separation helping me to spot otters is quite wrong.

No matter what bins we use, I spot more otters than Troubadoris.

So, another Troubador theory bites the dust:-O

Lee

Hermann said:

I totally agree. You can't have too much contrast, and high contrast requires, as I see it, high transmission (the higher the better), a flat transmission curve and excellent baffling to get rid of as much stray light as possible. "Too much contrast" makes no sense at all.

And if people are complaining that one particular binocular is "too bright", they need to put on sunglasses in bright conditions. Or ask the manufacturers to provide filter threads and appropriate filters. In some conditions, for instance on sunny days on snowy ground in the mountains, such filters would be very useful ideed. Some of the older binoculars, for instance the Russian ones, were provided with strong yellow filters for such situations.

Hermann

Click to expand...

Hermann, actually in some respect the HT could be called "too bright". I´d suggest for 8x42s the EDG, the Ultravid, the HT under easy conditions have basically the same great contrast transfer with very low veiling glare. The HT is brightest, making its colors look least saturated, and as shadows are less black than in the other two, the whole image might be perceived as less appealing. The Nikon is on the other end, with notably darker images, more crushed shadows, so it looks extremely contrasty, punchy and extremely colour saturated. Typical Nikon ED lens. The Ultravid is in the middle and just hits it perfect for my taste.

I´d love to see what the FL 8x42 images - the "darker" predecessor to the HT - look like.