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Heavy stuff!

nicolas claris

OPF Co-founder/Administrator
I’m back from Greece (yesterday night) but leave in an hour for Palma…

The complete Pentax gear ready to get into the plane cabin…
645D + 300 mm + 80-260 + 90 stabilisé + 55 + 25
An as back-up :
Pentax K3 + 21mm + 70mm
+ 2 x 2 To HD
Plus a MacBookpro…

10151171_10201949370201941_4758880899864733558_n.jpg
 
Heavy indeed, Nicolas.

Aside from the MacBookpro, much of the mass here consists of optical glass.

Wouldn't it be wonderful if someone, somewhere, discovered a light weight substitute for glass for photography lenses? Imagine a 600mm f/1.0 lens that weighed, oh, 5 kg or so. Sign me up, Scotty!
 

nicolas claris

OPF Co-founder/Administrator
A brilliant idea!
The actual stuff you see (including the MacBook Pro) weight 18 kgs… a challenge to get it accepted in plane canins… But I do have some tricks…
 

Asher Kelman

OPF Owner/Editor-in-Chief
Well for a start, Nicolas, I carry the camera body with a small lens and have another lens in my coat pocket! That's just as insurance for my bag going missing.

For me, for travel, the 90 mm stabilized lens could do most of the wide angle work too with stitching. It seems like a superb lens. BTW, have you seen any lens test results on these Pentax lenses in comparison to other MF lenses?

Asher
 

Doug Kerr

Well-known member
Hi, Tom,

Aside from the MacBookpro, much of the mass here consists of optical glass.

Wouldn't it be wonderful if someone, somewhere, discovered a light weight substitute for glass for photography lenses? Imagine a 600mm f/1.0 lens that weighed, oh, 5 kg or so. Sign me up, Scotty!

But its only the surface of the glass elements that do anything. Almost all the glass is just to fill the spaces between the surfaces they will be where they have the needed curvature.

Ah, Fresnel, where is thy sting!

Best regards,

Doug
 
Hi, Tom,



But its only the surface of the glass elements that do anything. Almost all the glass is just to fill the spaces between the surfaces they will be where they have the needed curvature.

Ah, Fresnel, where is thy sting!

Best regards,

Doug

Hey Doug,

Now that's something to ponder a while!

Tom
 

Asher Kelman

OPF Owner/Editor-in-Chief
Hi, Tom,



But its only the surface of the glass elements that do anything. Almost all the glass is just to fill the spaces between the surfaces they will be where they have the needed curvature.

Doug,

The issue is where the back of that front surface meets something with a different density. So the so-called "filler" is actually a "wave maintenance device". Without the rest of the optical glass in the lens, perfect uniformity of density, the light would be refracted and so diffused in a myriad of directions.

Asher
 

Doug Kerr

Well-known member
Hi, Jerome,

Aren't we trying to reinvent diffractive optics here?
Well, as for moi, I was invoking the concept of the Fresnel lens, something quite different from diffractive optics.

Not likely useful in photographic objectives, of course.

Best regards,

Doug
 

Asher Kelman

OPF Owner/Editor-in-Chief
Hi, Jerome,


Well, as for moi, I was invoking the concept of the Fresnel lens, something quite different from diffractive optics.

Not likely useful in photographic objectives, of course.

Doug,

Fresnels are marvelous in allowing a thinner lens. I wonder whether the aberrations caused by junctions between the concentric rings can be removed by some kind of deconvolution method?

Asher
 

Doug Kerr

Well-known member
Hi, Asher,

Fresnels are marvelous in allowing a thinner lens. I wonder whether the aberrations caused by junctions between the concentric rings can be removed by some kind of deconvolution method?

I don't know. I haven't looked for any evidence of work on this in the literature.

It would be wondrous if so!

Best regard,

Doug
 
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