4x lenses and objectives shootout

[ray_parkhurst]

Deleted OT post

[ChrisR]

a lot of them lying around

You Remind me of my box of odds and ends "lying about" since enlarging/printing days. Amongst the various Schneider compxxxxxx Rodenstock Roxxxxxx, Wray this and Dallmeyer that, there is indeed another Nikon 75mm I forgot I had.
Latterly I settled on an El Nik 50mm f/2.8, and 80mm f/5.6 and Componons longer, because they transferred all that I could get on to FP4 and Tri-X in Acutol, onto 20x24. I DO remember the joy in being able to make the change from 4 element lenses to 6, and seeing the improvement - particularly in the corners (though I can't remember what I did last week).
If you use two of them front to back, the aberrations add, of course, and if they're both near infinity that's close to doing a large print - and you'll need the corners for 1:1.
Coinimaging doesn't have any suitable lens to compare with unfortunately. As you say, the curves look ok, though I have no real way to judge what a difference in a curve does on the image.
So, well, dunno, sure worth a try if you already have one (or two, or three...). If it works reasonably well, then it would be good information. And maybe mine is/was a dud.
I posted a test a while ago at 1:1, which is only relevant if you're using it that way.

[ray_parkhurst]

Deleted OT post

[Tim M]

You never know.

Thanks everyone.

I should have at least mentioned the old lot of lens I do have on-hand (no extra budget required), mostly canon FD glass (thanks Dad!)

el-Nik 50/2.8
el-Nik 80/5.6 (never tried pairing it w/ the 50mm)
FD 28mm
FD 50/1.4
FD 50macro/3.5
FD 100/2.8
FD 135/3.5
and a few FD and EOS zooms, which I would guess aren't what we're looking for. And of course the FDs are 1.6x when mounted to my T2i.

And yes, I could get by with 2 or 3 descretes, say ~2.3x, ~1.7x, and ~1:1. I'm a BugGuide.net guy, so I'm usually only looking to fit whole beetles within the frame (still, I haven't been happy with the sharpness from the reversed el-nik 50mm in this magnification range)

So I guess the el-Nik 50 + 80 reversed should be the first try? I'll need to order a few new filter rings to get the two mounted to each other and the camera.

Or perhaps just buckle down, sell it all, and with the proceeds + budget get within striking distance of an MP-E 65mm (or at least the Canon 35mm/2.8 bellows lens)?

Thanks again,
Tim

[ChrisR]

Well that's 5040 combinations so we won't be hearing from you for a while...

Normally using the 100 prime and reversing the 50's onto it would be a first choice for me, but I believe FD lenses don't focus to infinity on an EOS without a nasty sounding adapter with a lens in it? (which I've never actually seen ) Prob there is that the 50mm is then getting its image from Beyond Infinity. Buzz Lightyear may approve, more than the lens designer.

[Blame]

If you use two of them front to back, the aberrations add, of course, and if they're both near infinity that's close to doing a large print - and you'll need the corners for 1:1.

Well not exactly. As I pointed out. When you revers similar lenses onto each other some of the aberrations subtract. Also while any lens induced blur is added the diffraction component is added only once.

Also you won't need the corners. A 75mm enlarger lens is for far bigger than APC-s or even 36mm wide sensors. That was the point. Using a longer focal length and 4 elements was always the budget solution to high definition.

Now for a quick question. What is the difference in glass design between a 6 element copy lens and two 3 element lenses placed face to face of double the focal length and F number if their design optimizes at infinity?

[Blame]

You never know.

Thanks everyone.

I should have at least mentioned the old lot of lens I do have on-hand (no extra budget required), mostly canon FD glass (thanks Dad!)

el-Nik 50/2.8
el-Nik 80/5.6 (never tried pairing it w/ the 50mm)
FD 28mm
FD 50/1.4
FD 50macro/3.5
FD 100/2.8
FD 135/3.5
and a few FD and EOS zooms, which I would guess aren't what we're looking for. And of course the FDs are 1.6x when mounted to my T2i.

And yes, I could get by with 2 or 3 descretes, say ~2.3x, ~1.7x, and ~1:1. I'm a BugGuide.net guy, so I'm usually only looking to fit whole beetles within the frame (still, I haven't been happy with the sharpness from the reversed el-nik 50mm in this magnification range)

So I guess the el-Nik 50 + 80 reversed should be the first try? I'll need to order a few new filter rings to get the two mounted to each other and the camera.

Or perhaps just buckle down, sell it all, and with the proceeds + budget get within striking distance of an MP-E 65mm (or at least the Canon 35mm/2.8 bellows lens)?

Thanks again,
Tim

Well by all means sell the FD glass. The el-nikkor's have too much potential to give up without a try. You will need a M39-M42 ring a set of M42 macro tubes or a bellows and finally a M42-(your camera) adapter. But as you can't do much playing around with macro without those basics no real problem. I would vote to stick the two lenses together with tape as a first try. If it doesn't work no loss. If it does then think how to get the glass as close together as possible. It may be that you just use more tape.

[ChrisR]

As I pointed out. When you revers similar lenses onto each other some of the aberrations subtract. Also while any lens induced blur is added the diffraction component is added only once.

The corner killing aberrations - Spherical, and Coma, add, no? Some chromatic too I believe, though I don't remember about that.

Also you won't need the corners. A 75mm enlarger lens is for far bigger than APC-s or even 36mm wide sensors. That was the point. Using a longer focal length and 4 elements was always the budget solution to high definition.

A budget attempt we all tried - still poor though for printing.
You'll need more of the corners in a combo than you would if you were using such a lens reversed, at M>1.
The 75mmf/4 I posted was poor at 1:1 even a few mm off centre.

Blame, having tried 4 element and 6 element enlarger lenses and shown a couple of results in the past: as far as I'm concerned, the budget 4 element versions are not worth bothering with. For a relatively small extra outlay they're easiy beaten, in whichever mode of operation tried. I really think the time would be better spent trying both types, rather than arguing why in theory they might not be too bad.

[Blame]

The corner killing aberrations - Spherical, and Coma, add, no? Some chromatic too I believe, though I don't remember about that.

Yes to that no. Lol.

From "Carl Zeiss lens design" here: http://www.cartage.org.lb/en/themes/art ... lzeiss.htm

"Symmetrical lenses

Meniscus lens with a stop in front exhibits barrel distortion, if turned around with the stop behind the lens, it reversed into a pincushion. If two were mirrored around the stop, the distortions cancel each other and leave a distortion-less system. It also corrects for lateral color (chromatic difference of magnification) and coma. Truly symmetrical lenses must be used at 1 to 1 magnification to totally cancel the three aberrations, and exhibit some very small amounts of transverse aberration at infinity. "

At least for 1x magnification it looks to me like an identical pair of lenses placed face to face is going to have a lot of freedom from distortion. That doesn't mean they will be necessarily sharp but the quality of design and manufacture will be least demanding when the quality field of view matches our requirements - that is APS-c or FF.

For combination close to 1x there is at least going to be a fair amount of cancellation. Nor are all distortions as bad for out purposes as they were for film enlarging. Coma is a pig but CA can be corrected in post processing while the big failing of 4 element lenses - poor corners is only a serious issue for stacking if the cause is not flatness of field.

I really think the time would be better spent trying both types, rather than arguing why in theory they might not be too bad.

But its fun! Why spoil the argument by actually going out and counting the horses teeth? I like theory.