Difference between projection lens, photo lens, & relay lens

[gekko]

What is the difference (if any) between a projection lens, a photo lens, and a relay lens? Thank you.

[lorez]

Hi gekko,

I hear these terms used interchangeably and sometimes combined, i.e. photo relay. It may be a bit like our recent discussion of the phase centering telescope.

lorez

[gekko]

Many thanks, lorez, for your reply.

[KurtM]

I've been watching this thread with great interest, as I thought it an excellent question. I suspected the terms were all headed in the same direction, but didn't know for sure. Seems to be a lot of this going around lately - just today I sat in two different woodworker's arguments over "try square" or "combination square", and "jig saw" or "saber saw"? Guess there are just some things in this world that refuse to be pinned down to just one name.

[lorez]

When not messing about with microscopes I also do a bit of woodworking, mostly making small boards from large boards... all in the name of boxes with drawers.

I know the difference between a combination square and a tri square, but am befuddled by the difference between a tri square and a try square. I can only guess that the tri square is for measuring the square angle of a right triangle while the try square is for attempting to get something square.

Where is my stamp collection ???

lorez

[gekko]

In Rod's post about connecting his Canon 60D camera to his scope ( viewtopic.php?f=9&t=2702 ), he is using a 10x photo eyepiece. I assume this is not the same as a photo lens or projection lens but is something else: as far as I know, a 2.5x projection lens gives about the right field of view for a full frame sensor, so this 10x photo eyepiece that is being used with a an APS-C sensor must be different from a projection lens or photo lens. Is it a normal eyepiece, but optimized for use in photography, that is then located a bit higher in the tube than it would be if it were used as an eyepiece (for viewing a virtual image)? Apologies for my confusion (and also if my questions are dumb ), and thanks for any clarification.

[gekko]

the try square is for attempting to get something square.
Where is my stamp collection ???

I think you'd better go in a hurry and look for your stamp collection .

[charlie]

In Rod's post about connecting his Canon 60D camera to his scope ( viewtopic.php?f=9&t=2702 ), he is using a 10x photo eyepiece. I assume this is not the same as a photo lens or projection lens but is something else: as far as I know, a 2.5x projection lens gives about the right field of view for a full frame sensor, so this 10x photo eyepiece that is being used with a an APS-C sensor must be different from a projection lens or photo lens. Is it a normal eyepiece, but optimized for use in photography, that is then located a bit higher in the tube than it would be if it were used as an eyepiece (for viewing a virtual image)? Apologies for my confusion (and also if my questions are dumb ), and thanks for any clarification.

Canon APS-C cameras are a factor of 1.6 to full frame. (35mm equivalent) So, 10x on an APS-C camera wouldn't equate to a full frame 10x.

With a Zeiss trinocular head, I'm using a normal 10x ocular in a short tube to attach a Canon 500D.

I had heard of a 0.5x lens being used in some Zeiss setups. Not that I am advancing solutions, just noting more variable methods to get an image.

[gekko]

Canon APS-C cameras are a factor of 1.6 to full frame. (35mm equivalent) So, 10x on an APS-C camera wouldn't equate to a full frame 10x.

With a Zeiss trinocular head, I'm using a normal 10x ocular in a short tube to attach a Canon 500D.

I had heard of a 0.5x lens being used in some Zeiss setups. Not that I am advancing solutions, just noting more variable methods to get an image.

What I meant was that a 10x projection lens was already far too powerful for a full frame sensor, let alone an APS-C sensor, so a "photo eyepiece" used with an APS-C sensor must necessarily be different from a "projection lens"; then what is a "photo eyepiece"?

[lorez]

I have found my stamp collection and will send you a letter.

In the mean time,

must necessarily be different from a "projection lens"; then what is a "photo eyepiece"?

It's old "rose by any other name", syndrome that we have been tossing about lately. They are the same thing.

Here is a link that details what Olympus has done.

http://www.alanwood.net/photography/oly ... s.html#125

lorez