Adapting Long Lenses on Sony E-Mount - Part VI

Part V is here

Putting it all together

So far, we have talked about all the parts required to mount longer lenses.  In this last installment, we are going to mount the Ross London 5 inch f4 Wide Angle Xpress lens, as an example how everything fits together. The 5 inch lens (equivalent to about 127mm) is not really that long, but fits in kind of a sweet spot; a Goldilocks focal length if you will, and I really like this lens (and the focal length).  Besides, I have been shooting with this lens in the last few days and it's already setup, therefore less work for me :)

The flange to sensor distance of this lens is roughly equivalent to its focal length.  This provides plenty of space to mount this lens on pretty much any current lens interchangeable digital camera, this includes all Sony E-Mount (or NEX-Mount).

Preparing the lens for the helicoid

The first thing to do, is to assess if the lens can be mounted on the helicoid. Some are easy and some are very difficult to do. Any lens that allows a standard filter size, like 49mm, 52mm, 55mm, 58mm, etc,. to be attached to its rear, would be the easy ones. The Ross London 5 inch f4 lens is one of those.  It allows a 55mm filter ring to be attached with just a little bit of work.  What we want to do is to epoxy a 55mm filter ring to the rear, and then screw the lens to the tube/helicoid for focusing.

The rear of the lens is just slightly too large to allow a 55mm filter ring to pass through.  We need to file the filter rim slightly with a Dremel grinding tool until the filter ring can go through.  Once it does, we can apply epoxy to the filter ring to attach itself to the lens.  Be sure to check that the filter is perfectly aligned, or else we will get pictures with one side sharp and one side soft.  Once the epoxy is set, it's ready to be used.

Mounting the lens on the helicoid

Now that the lens has a 55mm thread and ready to be mounted.  It's time to decide what combination of helicoid/tube/filter rings to use to get the lens to focus as closely as possible, but also able to focus to infinity.  The distance between the lens and the sensor is not long enough to stack two Vivitar 2X macro teleconverter helicoids; it's just slightly shy of infinity focus. This means I will be using just one helicoid, and extension tube/filter rings. As it turns out, all I needed was on extension tube and I didn't need any filter rings.  With the Vivitar 2X Macro Focusing helicoid and the filter rings, the minimum focus distance is about 5 feet, which isn't too bad, considering most old lenses have very long minimum focus distance.  If closer focus is needed, you can add two or three filter rings to extended the space between the lens and the helicoid.

Well, there you have it. Mounting a different lens just means adding or removing extension tubes/helicoid.  Hope you find this mini-series useful and helpful.  It has been a fun exercise for me.  Good luck if you are trying it out.

All the parts together from left to right: 1 mm thick M42 to E-Mount adapter, 42mm-62mm step-up ring, Vivitar 2X macro focusing helicoid, extension tube, lens with 55mm mount.

All screwed together

On camera

With Hood

Sample picture: Sony A7 & Ross London Wide Angle Xpress 5 inch f4

The Unmarked [AM] Ross London 5 Inch Wide Angle Xpress f4 Lens

I bought a pair of Air Ministry (AM) lenses from Henry's Outlet Store many years ago, one was the 5 inch f4 and the other was the 8 inch f5.6.  Both lenses were used by Britain's Royal Air Force on aircrafts to document the aerial combat or surveillance.  A search on the net would suggest that the 5 inch f4 lens was the same lens as the Ross London 5 inch Wide Angle Xpress f4, but I didn't see any evidence posted by anyone to verify this.  Last week I got another copy of this lens, which actually has both the manufacturer's as well as the Air Ministry's name and logo engraved on the lens.  So I compared them side by side, and they are, indeed, pretty much identical with very minor differences.

Side by Side - Aside from the engraved text, the lenses look pretty much the same

The mounting plate is slightly different.  Note the serial number on the Ross branded lens has a smaller number than the unnamed one.  This indicates that early lenses had maker's name on the lens, and later ones didn't.

Ref. No. 14A refers to photographic equipment.  Both the Royal Air Force and the Canadian Air Force use the same convention.

The major difference I see, is that the Ross branded lens has aperture settings to f32, while the unname lens only goes to f11.

Well, there you have it.  I am willing bet a dollar that the unnamed AM lens was made by Ross London, and the two lenses should be optically identical.  I haven't shot any pictures with the Ross lens yet, but will do so as soon as I get it mounted on my camera.