Here is my comparative review of the Zeiss Classic 10x40 T*P, and the new 10x42 FL. This review was lost in the server crash, so I post it again, with updates due to several months of use.
The FL is brighter, and not by a small margin. In low light conditions, the brightness is really impressive. However, I purchased the Classic in 1992, perhaps the coatings have been improved on the latest models.
The colour rendition is excellent, clearly better than the Classic, which has a yellow cast easily noticeable in direct comparison. But I find that the warm colours of the Classic are sometime more pleasant.
The contrast of the image is higher in the FL : black objects appear darker in the FL, even if the image is brighter.
I won’t comment on sharpness on axis, because I think now this is more a question of sample variation than a question of design. Off-axis, the falloff of sharpness is nearly identical in both binoculars. However, the FL suffers from a slight amount of field curvature, fortunately only visible when the binocular is tripod mounted.
In the outside 25% of the field, the Classic is better.
For my eyes, chromatic aberration is nearly identical in both binoculars, i.e. invisible on axis and moderate off axis. I can hardly see an improvement in the FL due to the fluoride glass.
There is a perceptible pincushion distortion in the FL, which gives sometimes a strange image on architectural objects. In the field however, I’m not bothered by this small amount of distortion. The Classic on the other hand has no perceptible distortion on static views, but shows a compression of the image near the edges on sweeping views, unlike the FL.
I’ve not noticed any flares in the FL. It happens rarely with the Classic, though it’s not a real problem.
The eye relief is 2 or 3 mm longer in the FL, which makes a clear difference for an eyeglasses wearer like me : I can always see the entire field of view, without pushing my glasses on my nose.
The closest focus distance is really 2 m, as advertised by Zeiss. (instead of 4.60 m for the Classic). There is no play at all in the focus mechanism, contrary to my Classic, which has furthermore different plays in right and left barrels, a flaw that really bothers me.
The focus wheel turns much more easily, and is twice as fast as the Classic :
To focus from 6 m to 30 m, the Classic requires 1/2 turn, and the FL 1/4 turn.
To focus from 25 m to infinity, the Classic requires 1/8 turn, and the FL 1/16 turn.
I can still achieve a very good focus, so it’s a nice feature for me.
The handling is better. The barrels of the FL are bigger, and this allows a stronger grip of the binocular, resulting in a more steady view. Because of the bigger body, the FL seems lighter than the Classic, despite it is not the case. The strap lugs are badly positioned in the Classic : the objectives are leaning against the belly when the binocular is held by the strap. In the FL the strap lugs are near the sides, so the binocular hangs nearly vertically and is far more pleasant to carry around the neck.
The FL comes with better accessories : a nice and wide strap, useful objective covers, a light eyepiece cover, and a very thick and protective case.
In conclusion, I’d say that none of the improvements listed above can justify in itself an upgrade from the Classic to the FL, but their sum can be worth it.
If I had to rank the improvements for my taste, I would rate :
1) the bigger shape of the FL, allowing a steady view
2) the longer eye relief
3) the excellent focus mechanism
4) the closest focus distance
5) the better image quality
This doesn’t mean that the improvement of optical quality is small, but it would be unfair to state that some details are visible in the FL and not in the Classic.
Jean-Charles