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Which Canon Macro Lens?

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However, magnification is not determined only by diopter-to-subject distance since that can be essentially zero.

 

I think we're both right, just talking about things in a slightly different way. I was talking about the diopter-to-subject distance being the sole determinant of the size of the virtual image being created. But, yes, for a given virtual image size, it's up to you to go as close or as far from it as you'd like, which will ultimately determine your 'magnification'.

 

I don't recall the power being +7.5 but considerably less

 

I've got a very old macromate myself, and it is indeed approximately a 135mm lens (i.e. +7.5 diopters). You can check this easily by setting the lens on edge on a ruler, having someone hold a flashlight pointing through the lens from a significant distance away, then moving a piece of paper along the lens axis until the light beam is focused to a point. This is the focal length, and the inverse is the diopter power (1/.135 = 7.5). I'm not sure if they've changed their lens over the years, but mine is 135mm.

 

Are you sure your maximum working distance is about 5"?

 

Yes, the macromate won't allow focus outside of about 5", regardless of what primary lens is used. With diopters, there's always the trade-off between magnification and working distance.

 

It never occurred to me that the SubSee was intended for cameras. Is this achromat designed for air or water? Is it +10 in air or water? Will you do larger ones for SLRs or will they remain 46mm? What is maximum focus distance?

 

We initially designed the SubSee as a hand magnifier for critter-lovers, but quickly realized it was a powerful macro-photography tool. It is a +10 in both air and water (the achromat is sealed in an airspace). We have a 52mm lens (same as macromate) which will be released along with a line of adapters for all DSLR and compact camera housings at DEMA. Here's a sneak peak of the adapter, with the current size lens (which is actually a 36mm diameter viewing area):

 

post-9396-1222796653.jpg

 

Maximum focus distance with the +10 version of the lens is about 10cm, but we should also have a few other powers, allowing more distance (but less magnification). Currently, with my Nikon D300 and 105mm lens and the SubSee in place, I get 2.2:1. I should point out, that even with the current small diameter SubSee, no vignetting occurs even at farthest focus (with my 105mm). The adapters will also support the Inon series of lenses.

 

But if I generally plan to go after a group of targets (eg, one site is good for octos, morays, very tame batfish and also cleaner shrimps), then the 50 + Macromate lets me get virtually all the shots that I could have gotten with the 50mm or the 100mm. I am probably giving up a little in IQ by using the 50 + MM instead of the 100, but for my needs, that is a fairly small loss and the increase in yield on the dive makes it worth it.

 

IMHO, you can't compare the 50mm+macromate to the 100mm. Although the 50mm will give you a wider angle of view, it is absolutely useless for macro photography since your working distance is so small already....putting a macromate in front of it just shrinks working distance down to almost nothing. In that regard, you actually LOSE flexibility when using the 50mm+MM pair. But when it comes down to it, I suppose it's all personal preference.

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Keri, this is OT but your diopter and the MacroMate have the same basic construction so I thought I ask...

 

There's two things that bother me about a sandwiched air diopter design. The first is simply the four extra interfaces. The second is, to me, more interesting and that's that I believe that the design is no longer an achromat. I'll explain.

 

The first flat port introduces CA that is reversed by the second flat port. If there were only air between the two it would be OK but there's a diopter that alters the angle of incidence of the light rays traveling through the air space. As a result, the second port does not correctly compensate for the CA introduced by the first. Even though the diopter in the middle may be an achromat, the system isn't once submerged.

 

There are multi-element diopters that are water-sealed, Inon and Epoque are two, but I don't know if these products are true water-contact achromats or not. I'd like to think that they are, but it's possible that they are simply air achromats that are repackaged with seals. These designs eliminate the extra interfaces of the SubSee/MacroMate but they lose power underwater. I would hope they would offer better CA correction but don't know.

 

I've downloaded software to attempt to model the system, but the software is expensive and unstable plus water has to be modeled as a lens element and I don't know how effective that is. I also don't know the design of the air diopters used. Have you looked carefully at the chromatic aberration characteristics of your diopter and can you comment?

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I agree that this is definitely way off topic now...maybe a new thread should be started to discuss optics further, since this interesting discussion is currently undercover?

 

An achromat is an optical system that attempts to bring two wavelengths of visible light into the same focal plane. So, when you introduce other elements into the system, wouldn't it still be classified as an achromat, since it is still doing its job, just not as well. The introduction of two ports into the design really doesn't change the amount of CA a significant amount, since light rays for macro photography hit the lens at very small angles. CA is much more apparent when there are high angles of incidence (like when doing wide angle photography).

 

I just checked out the lenses you pointed out online, and I've noted a few things...first, one is described as being a "2X" lens....that sends up a flag already, since such a claim makes no sense (since magnification achievable is dependent on the primary lens focal length). One is also described them as being "4 elements in 4 groups"...well I suppose you can say that, if you claim the ports on either side of the diopter to be "elements" also. In that case, the Macromate and SubSee are also "4 elements in 4 groups". My understanding of these products is that they are indeed 'air achromats' sealed in an airspace, in the same way that the MacroMate and SubSee are. I could be way off though, since I've never actually had my hands on either of these.

 

When you consider wet versus sealed lenses, you have to consider the fact that leaving a lens open to the water will decrease magnification power by 66% (as you mentioned)...so although you may "add" CA to the diopter system by sealing it, you make possible something that would otherwise be completely IMpossible to achieve from a wet lens. For example... the SubSee is a 100mm (+10 diopters) lens underwater....to produce an equivalent wet lens, it would have to be a 33mm lens, which has a radius of curvature somewhere near the size of a large marble.....not the best for macro photography :offtopic: CA would be the LEAST of your worries with a lens like that.

 

I haven't taken any CA test shots (against a fine grid) yet, but should have these finished in the next few days, as I'm frantically preparing literature for DEMA right now... I will let you know when I find out. I'm curious to see myself! I CAN tell you that I've picked apart several of my images taken with it, and can't see any problems....fingers are crossed for the tests though...

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An achromat is an optical system that attempts to bring two wavelengths of visible light into the same focal plane. So, when you introduce other elements into the system, wouldn't it still be classified as an achromat, since it is still doing its job, just not as well. The introduction of two ports into the design really doesn't change the amount of CA a significant amount, since light rays for macro photography hit the lens at very small angles. CA is much more apparent when there are high angles of incidence (like when doing wide angle photography).

Yes, that's the definition and it's possible that the end result still meets it. CA of macro flat ports is significant since I tend to max out my CA compensation in Photoshop. I can accept that the combination of the three components might produce negligible CA but I'd like to see for sure.

 

I just checked out the lenses you pointed out online, and I've noted a few things...first, one is described as being a "2X" lens....that sends up a flag already, since such a claim makes no sense (since magnification achievable is dependent on the primary lens focal length). One is also described them as being "4 elements in 4 groups"...well I suppose you can say that, if you claim the ports on either side of the diopter to be "elements" also. In that case, the Macromate and SubSee are also "4 elements in 4 groups". My understanding of these products is that they are indeed 'air achromats' sealed in an airspace, in the same way that the MacroMate and SubSee are. I could be way off though, since I've never actually had my hands on either of these.

I can't speak for the design of all of these products but I believe that at least one has curved glass surfaces. I prefer the 67mm Inons to the MacroMate for handling reasons and because I like a weaker wet diopter. I haven't tested them side by side. I agree that the claim of 4 elements in 4 groups is a joke, perhaps even moreso than the ridiculous "2x" marketing nonsense.

 

When you consider wet versus sealed lenses, you have to consider the fact that leaving a lens open to the water will decrease magnification power by 66% (as you mentioned)...so although you may "add" CA to the diopter system by sealing it, you make possible something that would otherwise be completely IMpossible to achieve from a wet lens. For example... the SubSee is a 100mm (+10 diopters) lens underwater....to produce an equivalent wet lens, it would have to be a 33mm lens, which has a radius of curvature somewhere near the size of a large marble.....not the best for macro photography :offtopic: CA would be the LEAST of your worries with a lens like that.

Power reduction is a consideration but I'd say not everyone sees +10 as the goal. A +10 is too strong for a 70-180 zoom and too strong for a 150mm (my two lenses), but I agree that if +7.5 or +10 is the goal then your approach is the right one.

 

I haven't taken any CA test shots (against a fine grid) yet, but should have these finished in the next few days, as I'm frantically preparing literature for DEMA right now... I will let you know when I find out. I'm curious to see myself! I CAN tell you that I've picked apart several of my images taken with it, and can't see any problems....fingers are crossed for the tests though...

I think that's good news and I'm glad to see more options and competition. Good wet diopters are valuable and your mount looks more buoyant than the MacroMate. :P

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Yes, that's the definition and it's possible that the end result still meets it. CA of macro flat ports is significant since I tend to max out my CA compensation in Photoshop. I can accept that the combination of the three components might produce negligible CA but I'd like to see for sure.

 

WOW, that's surprising! I'll definitely check things out in depth. I tend to think the extra ports won't do much, but I seem to be on a streak of being wrong about things....so we'll see.

 

I can't speak for the design of all of these products but I believe that at least one has curved glass surfaces. I prefer the 67mm Inons to the MacroMate for handling reasons and because I like a weaker wet diopter. I haven't tested them side by side. I agree that the claim of 4 elements in 4 groups is a joke, perhaps even moreso than the ridiculous "2x" marketing nonsense.

 

I am curious to see what magnification loss would result if only one side of the achromat is air-tight....maybe that's how the Inon is designed, since I do remember seeing on a website somewhere, that 2 different diopter powers were quoted for each lens. I need to get my hands on one to check it out.

 

Power reduction is a consideration but I'd say not everyone sees +10 as the goal. A +10 is too strong for a 70-180 zoom and too strong for a 150mm (my two lenses), but I agree that if +7.5 or +10 is the goal then your approach is the right one.

 

True, not everyone wants to go SUPER macro. Though, with a +10 combined with 100mm/105mm lens, a perfect magnification range is achieved (without it - up to 1:1, with it - 1:1 to 2.2:1). I'd kill to have a 150mm macro.... maybe if I sell a few dozen of these SubSees :offtopic:

 

I think that's good news and I'm glad to see more options and competition. Good wet diopters are valuable and your mount looks more buoyant than the MacroMate. :P

 

Definitely is....the MacroMate I have (non-hinged version) is about 570g, while our adapter/lens combo is 230g. But I mean to take NOTHING away from the macromate, as it's a very solid build, and is in general very high-quality. Kudos goes out to Berkley/the designers in charge of it.

 

What wet diopter(s) do you use, if you don't mind me asking? (you may have said somewhere in the previous posts, but it's late, and I'm too tired to check....)

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I use the Inon 330 because I find it easier to use with the long focal lengths. Inon offers a 167 as well and I've tried the Epoque. I frequently have a +1.5 installed on the lens already. I am uncomfortable shooting subjects closer than a certain working distance so really high power doesn't help me.

 

Inon says the following here:

 

"The lens is constructed of two plano-convex high quality optical glass elements in two groups."

 

That appears to be the case when I examine it. The outside surfaces are flat on the 330 and the air gap seems too small to contain more elements.

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I use the Inon 330 because I find it easier to use with the long focal lengths. Inon offers a 167 as well and I've tried the Epoque. I frequently have a +1.5 installed on the lens already. I am uncomfortable shooting subjects closer than a certain working distance so really high power doesn't help me.

 

Inon says the following here:

 

"The lens is constructed of two plano-convex high quality optical glass elements in two groups."

 

That appears to be the case when I examine it. The outside surfaces are flat on the 330 and the air gap seems too small to contain more elements.

 

To each his/her own, I suppose. Do you think it's worth it for us to offer a lens similar to the Inon 330 and 165 (+3 and +6) in addition to the +10?

 

I'd really like to get my hands on the Inons, just to take it apart and analyze the lenses they've used. After reading that they are indeed using a pair plano-convex lenses, I've been sitting here wondering how the optics of this system work. My neighbour has promised me some optical design software that he's been using for developing microscopic photography equipment for cellular biologists....can't wait to get my hands on it, but I fear it might be way over my head.

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Do you think it's worth it for us to offer a lens similar to the Inon 330 and 165 (+3 and +6) in addition to the +10?

 

I'd really like to get my hands on the Inons, just to take it apart and analyze the lenses they've used. After reading that they are indeed using a pair plano-convex lenses, I've been sitting here wondering how the optics of this system work. My neighbour has promised me some optical design software that he's been using for developing microscopic photography equipment for cellular biologists....can't wait to get my hands on it, but I fear it might be way over my head.

It would be a good choice for people with longer focal lengths. As for a business case, I don't know. You'd compete with Inon rather than Macromate and you have a mount that some may prefer over Inon. I would use whichever offered better IQ.

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I think we'll end up offering a few lenses to match the powers of the MacroMate and the Inon lenses.

 

Thanks for the input and the nice optics discussion, Craig.

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