Lens reversal issues

[480sparky]

Start by mounting the longest focal length lens you have to the camera, and if it's a zoom, zoom to the longest FL. If that doesn't eliminate the vignetting, it will at least reduce it as much as possible. You'll just need to crop your images in post.

 

[jowensphoto]

I've never used the reverse mounts but I do a lot of free lensing/reverse macro. I'm going to guess no, but I'm assuming that you have no aperture control with the reverse mounts? With Canon, you can lock the aperture by first setting the aperture to what you need/want, then hold down the DOF preview while taking the lens off. Aperture is then locked!

 

[Judobreaker]

Depends a bit on the lens.
With my Nikon 50mm D lens I can set aperture manually using the aperture ring it has. ^^

 

[480sparky]

When you reverse one lens onto another, you want to have the reversed lens wide open.

 

[Judobreaker]

Yes, that be true.
I forgot we're talking about stacking here.

 

[Helen B]

Also, to figure out the magnification ratio, divide the focal length of the long lens by the focal length of the short lens. I.E. - a 50mm mounted on a 200mm will give you 4:1.

I can't remember where I first read that, or why it's true, but it is - lol.

It doesn't matter which lens is on the front, but I would put the heavier lens on the camera.

The basis for that guide is so simple you will kick yourself.

It applies when the rear lens is set to infinity, which means that the light from an in-focus object is arriving at the rear lens in parallel. That means it left the front lens in parallel, so the object must be where the front lens' image plane would be if the front lens were mounted normally on the camera and focused on infinity.

Therefore, in this particular case:

Object distance = focal length of front (reversed lens)

Image distance = focal length of rear lens

but

Magnification = image distance / object distance

Therefore

Magnification = focal length of rear lens / focal length of front reversed lens.

As already mentioned, the magnification will be higher when the rear lens is focused closer.

 

[jowensphoto]

When you reverse one lens onto another, you want to have the reversed lens wide open.

Ooooooh! Ok. I see what you guys are talking about now.

 

[480sparky]

When you reverse one lens onto another, you want to have the reversed lens wide open.

Ooooooh! Ok. I see what you guys are talking about now.

There are two 'reversing lens' methods.

One is to reverse ONE lens around on the camera:

Using a lens that has no aperture ring is near impossible......you'll need a way to control the aperture. Since the electronic and mechanical connections between the camera and lens are broken, you must control the aperture manually. I've heard Canon will let you use your DOF Preview button to 'set' the aperture of a lens before you remove it, but then when you reverse the lens you're looking at a dark viewfinder. Not very practical if you're stopping down to f/8 or smaller.

Nikon users can enjoy the benefit of a BR-6 (shown mounted on the lens above), which is an adapter that mounts onto the rear of the lens and has both a lever and a cable release connector to allow you to frame, compose & focus with the lens wide-open, then actuate the adapter manually just before shooting. However, this works best with lenses that have an aperture ring.... newer G-class lenses can only be utilized with any accuracy at their minimum apertures. This may not be ideal due to diffraction.

To buy an adapter like this, you'll just need to get one that has both your lens mount system and the size of the filter for the lens you want to reverse. Mine is a Nikon F/52mm.



The other method is to get a filter-thread reversing ring, sometimes called a macro coupler.

It's basically a ring with two filter threads, each sized to the two lenses that are used. You can buy these adapters for a couple dollars on ebay. Just find the two filter sizes of the lenses you want to use and order one. Mine is a 52/52.

This basically turns one lens into a high-end close-up filter. You'll want to use the reversed lens wide open, as you will be using the aperture of the lens mounted to the camera to control exposure (and DOF) as you normally would. This method favors Canon as you can 'open' the aperture of the reversed lens using the DOF Preview trick mentioned above to it's largest (smallest f/number), and control the exposure as your would normally. Nikon users, if using a G-class lens, will either need to manually hold the aperture control tab of the lens open manually, or can use a BR-6. Since I have D-class lenses, I can just unlock the aperture ring and open my 50 to f/1.8.

 

[jowensphoto]

Thanks for the explanation of the two differences! Re: dark view finder on Canon using the DOF/lens removal aperture control method. I've never had issues with a dark view finder. I've used my 50 1.8 at f/22.

 

[jowensphoto]

On second thought, probably because I free-lens rather than use an adapter... so that probably has something to do with it.

 

[480sparky]

Thanks for the explanation of the two differences! Re: dark view finder on Canon using the DOF/lens removal aperture control method. I've never had issues with a dark view finder. I've used my 50 1.8 at f/22.

I don't get it.... how can you NOT have a dark VF with your lens stopped down to f/22?

 

[jowensphoto]

It's not dark. I'm tellin' you lol I will take some this weekend and report back.

 

[480sparky]

It's not dark. I'm tellin' you lol I will take some this weekend and report back.

Look through the lens when it's off the camera.... are the aperture blades closed down? If not, you're not shooting at f/22.

 

[jowensphoto]

I'm totally sure. When I first started trying the techniques, I liked the shallow DOF of using 1.8 while doing RM/Free lensing but quickly found it limiting. So I researched how to set the aperture and began closing it up more.

I only have the Minolta 35mm with me today, but I'll try to take something interesting at the truck pull this evening lol

 

[480sparky]

I'm totally sure. When I first started trying the techniques, I liked the shallow DOF of using 1.8 while doing RM/Free lensing but quickly found it limiting. .......

If your VF is just as bright with your freelens set at f/22 as it is set at f/1.8, you've somehow managed to violate the laws of physics.

I'm gonna report you the the Optics Police, and Isaac Newton will be along shortly to arrest you.