Mirror lens, by Centon

[Stephen]

A new Centon Mirror lens, a Korean made 500mm T2 Type mount, on an Olympus PM-1. The shots are all hand held at high ISO to see what it can do, not too bad if you can focus it! Only cost £40, Ebay, used but as new condition with filter pack of four, so not expecting miracles from it. the filters are all ND type, no red or yellow for B/W.

Despite being 500m F8, it behaves as a 1000mm F8 on the Micro 4/3 format. It has an excellent close focus macro range, down to under 5 feet on the helical focus screw.


First Test shot on flag at 144 yards


Test shot of building at .90 miles


Shot of house, focus on aerial at .5 miles


Couple in playing field, 150 yards.

Testing next with and without the filters, and with an aperture cap to increase the DOF a bit. It will be fitted to a Slik heavy duty tripod as well.

I'l try some B/W with strong red filtration, that usually increases the contrast and apparent sharpness, as do polarisers on colour shots.

Stephen.

[julio1fer]

Nice results.

I have a Vivitar 500mm f/8 which is also a T mount. Hard to focus well but quite useful, how else would you get 500mm (or 1000 in 4/3) for the weight and size of a large normal?

Try pointing the lens to reflections of the sun in moving water, and get the bright points out of focus - it looks like this:



I have been meaning to point the lens to bright color neon sign, to see what happens with the OOF rings.

[olroy2044]

Try pointing the lens to reflections of the sun in moving water, and get the bright points out of focus - it looks like this:

How interesting!  That photo looks just like one I took of the light and shadow that a solar eclipse produced on the wall of my house.  The light was shining through the leaves of a tree and produced this pattern on the front of my house:



Roy

[Stephen]

Mirror lens always produce the Doughnut patterns, there are not noticed in the out of focus smoother areas, but bright points always produce them.

They become even more distinct if the lens is stopped down, and yes, mirror lens can be stopped down, despite what is often said.
You use a lens cap with a hole in it to reduce the outer diameter and a cap with a disc added to the central mirror on the front.(or tape on cardboard discs).

The reduced ring acts just like any other lens and you get increased depth of field, but it is very slight!!
You also get very sharp doughnuts!

Adding things to the front of a lens reminds me about the Garatso lens use in Hollywood, an amazing patented lens that focused on both the foreground and the background, with enormous depth of field.

It used glass elements but had a special front ring lens that focused separately, supported on a web of thin wires, and a fresnel edge to smooth the break between the two elements in focus. The front looked very odd, but the lens work fine on several major 1950 productions in Black and White.....till they tried it with Technicolor, and realised that it produced rainbow coloured doughnuts and coloured edges around any bright spot!!!

This had not shown much in B/White, but made the lens totally useless for colour films. Oddly it's failure lead to the early 1950 rush to 3D, which also promised great depth of field.

That failed as well, too many headaches!! but Vistavision tried a double focus lens later on and that worked. It used two lenses, one close, one far, combined in a complex prism and mirror system to align them. Depth of field was three feet to infinity.....excellent for cinema work.

Stephen.

[truls]

I don't get it how you are able to focus this 500mm lens on Olympus digital, especially the english flag pic...

The picture of the house at .5 miles has details, the window blinds are visible, not bad. Does lenses get artificial better due to lesser use of lens area?

[mickeyobe]

Apr 24, 2013 19:45:08 GMT -5 julio1fer said:

Nice results.


Try pointing the lens to reflections of the sun in moving water, and get the bright points out of focus - it looks like this:



I have been meaning to point the lens to bright color neon sign, to see what happens with the OOF rings.

Or go to a Tim Horton's Donut Shop and snap/snack away.

Mickey

[hansz]

It even allows a bit of hand holding

You're hand holding this?


IMG_0969 by hanszeiss, on Flickr

MTO 1000 with a Nex3 'attached'. And fun to use!

Hans

[Stephen]

The Centon is only 500mm and as small as a fat 135, and can just about be hand held due to the light weight, no way can the MTO be hand held.

There's no tripod bush on the Centon, but one can be added to the Micro 4/3 adaptor, some makes have them already, but a collar clasp can added. But it is so light that it does not seem to strain the mount.

At the moment the T2 is Exakta, and an Exakta micro 4/3 adaptor, which gives a sound tight mount. I have a T2 to Micro 4/3 solid adapter on order, which will be adjusted to give a good infinity setting as at the moment it goes well beyond infinity.
It is also has a parallel outside tube so can have a tripod mount added easily.

I think I have solved the manual focusing problems with the Pen cameras, and the issue of the costly EVF, home made, but works, a rear hood with a simple +10 dioptre lens. The view is far better than the EVF, even in strong sunshine, I will post the details separately very soon.
Stephen.

[Stephen]

After struggling today to test a Tamron Converto 135mm I have come across a problem with digitals and that's the IS and long lenses, I had left the IS on with the mirror lens, and now will try without and a Monopod / Tripod to see if it improves.

The Tamron proved so sharp that it out resolves the sensor, and I wonder if this partly hapens on the mirror lens at the exact point of focus.

The sharpest point can only be a pixel, and fine resolution is limited by the squares and gives a jagged look to fine detail, and that was present with some of the Centon test images. With the narrow DOF and the jagged look, and it then gives the impression of out of focus overall, helped by the low contrast.

I will knock up a big lens hood in plastic, and then repeat the test shots on a Monopod or heavy duty Slik tripod, I am pretty sure more performance can be squeeze from the Centon Mirror Lens.

Stephen.

[Stephen]

The Centon does not like a 2x added, it makes an image, but is too soft to use. You get a better result by cropping. It may be the make does not match, It's a Vivitar, and works with shorter prime lenses very well. The main improvement will be a decent hood next.

Stephen.