Macro Macro question - would only some lenses work in reversing setup?

ohaya · 02-14-2016, 03:46 PM

Hi,

I've been experimenting with trying to taking macro images with "what I have", i.e., with various parts that I have, and I was kind of surprised/happy that I was able to use the following with my K-r:

- A 55mm f/1.8 M42 lens
- A reversing ring (49mm-to-something (I think it was a T-mount)
- A T-mount-to-M42 adapter
- An M42-to-K-mount adapter

Here's a pic that I was able to take with the above arrangement:

I figured that since that worked, I'd try to use a 135mm M42 lens I had, but when I tried that, it seemed like I could not get that arrangement to focus anywhere, either close or far.

I guess that, at the beginning of these "experiments", I assumed that if I got the configuration to work with one lens, that any lens would work, maybe with different closest focus distance and magnification, but that it would still work (== be focusable).

So is that "normal" that when using reversing a single lens, that only some lenses would work? Did I just get lucky with the first try with the 55mm lens?

What kind of setup might give me more focus distance but approximately the same magnification?

Thanks,
Jim

Lake · 02-14-2016, 05:28 PM

You may need a long extension tube. Hold your reversed 135mm lens about 6 inches in front of the camera and move back and forth. The object should come into focus. It will help to have plenty of light.

ohaya · 02-14-2016, 06:08 PM

Originally posted by Lake

You may need a long extension tube. Hold your reversed 135mm lens about 6 inches in front of the camera and move back and forth. The object should come into focus. It will help to have plenty of light.

Do you mean to do that with another lens already installed on my K-r? Or just looking via the mirror directly to the front end of the reversed 135mm?

EDIT: I just found this page:

Best Lens for Reverse Macro - Photo.net Pentax Forum

In the discussion, there is this:

Quote:

On a simple reversing ring, the longer the lens, the less likely it will be able to achieve focus. That's why simple reversing rings are normally only used with wide angle lenses. He's got the right lens. A 28mm is useful, fairly high magnification. A 35mm will end up around 1:1, a 50mm around 1:3 (1/3x), and an 85mm will focus past infinity.

So I guess that the 135mm is probably a no-go for using just a single lens on a reversing ring?

tryphon4 · 02-15-2016, 01:16 AM

A reversed lens is equivalent to a close-up lens, its power is given by this formula: power=1000/F (power unit is δ (in diopter), F is the focal length (in millimeters)).
So a reversed 50mm is equivalent to a 20 diopter close-up but a reversed 135mm is equivalent to a 7.4 diopter close-up.
It is a better idea not to use the reversed lens alone but to mount it on a standard lens (e.g. a 50mm F/1.7 or F/2), it will be far easier to focus.

The purpose of using close-up, reversed lens or extension tube is always the same: decrease the lens register.
A wide angle has a short register, if you increase it slightly, you gain a lot of macro power ; a tele lens has a long register, you will have to increase it a lot to gain a bit of macro power.

Last edited by tryphon4; 02-15-2016 at 01:37 AM.

02-14-2016, 03:46 PM	#1
ohaya Senior Member Join Date: Jan 2016 Posts: 242	Macro question - would only some lenses work in reversing setup? Hi, I've been experimenting with trying to taking macro images with "what I have", i.e., with various parts that I have, and I was kind of surprised/happy that I was able to use the following with my K-r: - A 55mm f/1.8 M42 lens - A reversing ring (49mm-to-something (I think it was a T-mount) - A T-mount-to-M42 adapter - An M42-to-K-mount adapter Here's a pic that I was able to take with the above arrangement: I figured that since that worked, I'd try to use a 135mm M42 lens I had, but when I tried that, it seemed like I could not get that arrangement to focus anywhere, either close or far. I guess that, at the beginning of these "experiments", I assumed that if I got the configuration to work with one lens, that any lens would work, maybe with different closest focus distance and magnification, but that it would still work (== be focusable). So is that "normal" that when using reversing a single lens, that only some lenses would work? Did I just get lucky with the first try with the 55mm lens? What kind of setup might give me more focus distance but approximately the same magnification? Thanks, Jim

02-14-2016, 06:08 PM	#3
ohaya Senior Member Join Date: Jan 2016 Posts: 242 Original Poster	Originally posted by Lake You may need a long extension tube. Hold your reversed 135mm lens about 6 inches in front of the camera and move back and forth. The object should come into focus. It will help to have plenty of light. Do you mean to do that with another lens already installed on my K-r? Or just looking via the mirror directly to the front end of the reversed 135mm? EDIT: I just found this page: Best Lens for Reverse Macro - Photo.net Pentax Forum In the discussion, there is this: Quote: On a simple reversing ring, the longer the lens, the less likely it will be able to achieve focus. That's why simple reversing rings are normally only used with wide angle lenses. He's got the right lens. A 28mm is useful, fairly high magnification. A 35mm will end up around 1:1, a 50mm around 1:3 (1/3x), and an 85mm will focus past infinity. So I guess that the 135mm is probably a no-go for using just a single lens on a reversing ring? Last edited by ohaya; 02-14-2016 at 06:23 PM. Reason: Add info found

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02-14-2016, 05:28 PM	#2
Lake Senior Member Join Date: Jun 2015 Location: Minnesota Posts: 104	You may need a long extension tube. Hold your reversed 135mm lens about 6 inches in front of the camera and move back and forth. The object should come into focus. It will help to have plenty of light.

02-15-2016, 01:16 AM	#4
tryphon4 Pentaxian Join Date: Apr 2011 Location: Drome, France Posts: 304	A reversed lens is equivalent to a close-up lens, its power is given by this formula: power=1000/F (power unit is δ (in diopter), F is the focal length (in millimeters)). So a reversed 50mm is equivalent to a 20 diopter close-up but a reversed 135mm is equivalent to a 7.4 diopter close-up. It is a better idea not to use the reversed lens alone but to mount it on a standard lens (e.g. a 50mm F/1.7 or F/2), it will be far easier to focus. The purpose of using close-up, reversed lens or extension tube is always the same: decrease the lens register. A wide angle has a short register, if you increase it slightly, you gain a lot of macro power ; a tele lens has a long register, you will have to increase it a lot to gain a bit of macro power. Last edited by tryphon4; 02-15-2016 at 01:37 AM.