Andy. I agree on the FL's. They are still competitive with any alpha out there today. One of the best for CA control and we all know Henry likes his 8x56 FL and I like my 8x32 FL and 8x42 FL. With the plastic body they are light, strong and comfortable to use also. With the big AK prisms they are brighter and sharper on-axis than the Swarovski EL. I notice the difference in transmission with the AK prisms and contrast and on-axis sharpness seems better also. The binoculars I have with it are brighter and sharper like my Zeiss Conquest HD 8x56, my Zeiss FL 8x42 and my two Vortex Razor's UHD 8x42 and 18x56. The AK necessitates a slightly longer and heavier binocular but it is worth it. I am surprised Zeiss didn't use an AK in the SF. The designers are more worried about form over function. Form sells more binoculars and the normal person probably won't notice a 5% improvement in transmission between an AK prism and an SP. Here is a list of binoculars that have AK prisms.
The 32mm FL does not have AK prisms. I too would like to see more of them, but is there good evidence that they contribute to contrast or sharpness? (I'd like to think so given the lack of dual-purpose surfaces, but am not sure.) Perhaps it's just that you're looking at a sample of generally larger binos that stop down well in daylight. I was also surprised the SF couldn't find room for AK prisms, given its size. As for transmission, the difference often seems less than 5%. Between Swaro SLC and EL for example, it's more like 3%. (Coating differences must make comparison tricky.)
Your right The FL 8x32 has SP's because Zeiss wanted to make it short and compact and there was no room for an AK. Everytime I use my FL 8x32 I get to thinking it is really good and it is for a 32mm but then I switch to my FL 8x42 and it is much brighter and sharper on-axis with better contrast also. The bigger aperture pulls in 70% more light and those AK prisms transmit a lot more light. On the SF they were going for that forward balance and ergonomics over sheer performance. Swarovski says 90% transmission on the 42mm EL and 93% on the 56mm SLC. Allbino's says 94% transmission on the 8x42 FL, 8x56 FL and the Conquest HD 8x56.
Your right that the 8x42 FL is going to pull in a lot more light than the 8x32 FL especially in low light situations and the aperture has more to with it than the AK prism. When I really notice the difference in prism type is when I compare my three 8x42's. The Zeiss FL 8x42 and Vortex Razor UHD 8x42 with the AK's are always brighter than the Nikon EDG II 8x42 with the SP with my eyes. Same aperture, all have quality glass and high quality coatings. I am not saying the AK binoculars are overwhelmingly superior. I am saying they are brighter. It is a known fact despite your blabbering that the AK transmits at a higher efficiency than the SP. If it isn't so why does Zeiss use the AK in their HT binoculars which are designed for low light. I know what I see and your trying to convince me it isn't so isn't going to change my mind.
Andy. I really never noticed it in the field either until I started comparing these three 8x42's back to back. I have never compared similar binoculars with the two different prism designs until now. It is very noticeable IMO.
I am not saying every AK binocular is superior to every SP binocular. It just surprised me the difference in brightness between these three binoculars and the AK logically seemed to be the underlying reason. I would speculate if an SP binocular has higher transmission than an AK binocular it has better glass, better coatings or less air to glass surfaces in the optical design because the AK is always going to be an inherent advantage. Using the Nikon WX 10x50 isn't really a fair example of the advantages of an AK prisms high transmission because it is a very complex binocular and has many air to glass surfaces to achieve the astounding FOV it achieves. It is literally chock full of glass. Notice they did use an AK prism probably to keep the transmission to acceptable levels. That example means NOTHING. I agree that some people may prefer the lighter smaller body of an SP prism binocular. That is probably why Zeiss didn't use one in the SF. Form over function sells more binoculars. But they did keep the weight down on the FL's with the plastic bodies and the use of high fluorite glass to keep the focal length down. You do have to decide if you want ultimate performance or you want a more compact binocular. The Vortex UHD's are certainly longer and heavier because of the AK prism but IMO the performance is worth it. The transmission on the Zeiss 8x42 FL is 94% and the transmission on the Nikon EDG 8x42 is 90% and I could not find any transmission figures on the Razor UHD but I bet it is around 94% also.
