Wanted Cheap wet lens 52 or 67 thread

[stepfen]

I've asked exactly the same question some time ago. Cheap top side close up lenses need nothing more that a single glass element, hence the light passes through "air glass air" path. Water has very different optical properties compared to air (actually very similar to glass). Underwater "air glass air" becomes "water glass water" and now the same topside lens doesn't add practically any magnification (a diopter +6 topside becomes something like +1.2 underwater if I remember the numbers correctly ).
Interestingly lenses designed for underwater work topside as well! That's because they have several sandwiched elements (hence much more expensive) and their closing up effect is happening in the inner sandwiched elements. What medium is outside them doesn't affect them much. I hope that helps

 

[tarponchik]

I've asked exactly the same question some time ago. Cheap top side close up lenses need nothing more that a single glass element, hence the light passes through "air glass air" path. Water has very different optical properties compared to air (actually very similar to glass). Underwater "air glass air" becomes "water glass water" and now the same topside lens doesn't add practically any magnification (a diopter +6 topside becomes something like +1.2 underwater if I remember the numbers correctly ).
Interestingly lenses designed for underwater work topside as well! That's because they have several sandwiched elements (hence much more expensive) and their closing up effect is happening in the inner sandwiched elements. What medium is outside them doesn't affect them much. I hope that helps

I do not understand the logic of the process because refraction goes back and forth, water-glass and then glass-water. But I'll see soon.

 

[tursiops]

I do not understand the logic of the process because refraction goes back and forth, water-glass and then glass-water. But I'll see soon.

Think of it as magnification depending on the ratio of the two refractions...twice, once going into the lens, once coming out.

 

[Interceptor121]

I am selling a IDAS UWL-04 for £200 it has both m52 and m67 thread

 

[Barryattle]

I'm currently using a cheapo M67 +10 Opteka I bought on eBay for maybe $25; I think it's a 2-element lens. Works fine. I don't have a clue whether it gets me the same magnification as an expensive +10 designed for underwater use like a SubSee, Fantasea, etc. But it does give me some additional magnification. I'll have to see if I can borrow an official wet macro lens sometime to see if there is any appreciable difference.

 

[tarponchik]

Well, I checked it in my kitchen sink and indeed, the 10x lens only gave me about 1.5x magnification when underwater. Here is an old tread on the topic.