Big-Koi

I have an Olympus Pen F, plus an adapter that allows me to mount vintage Pentax screw mount lenses, and that is the way I am leaning.
I am also considering an Olympus OM 50mm/f3.5 macro lens, but will have to also get an adapter.
I am not sure that either of the above lenses will yield I:1 images.
Are there any other vintages lenses that I should consider that will yield 1:1 images?

Thank in advance for your input,
Big-Koi :

BebuLamar

All true macro lenses (and the Pentax 50mm f/4 macro included) will yield a 1:1 magnification on the 4/3 camera with the appropriate adapter. The image will appear to have higher magnification than an image from a 35mm camera. (and I said appear to have higher magnification but the magnification is still 1:1).

RWR Loc: La Mesa, CA

If you can extend it 50mm beyond it’s native flange focal distance, 1:1 can be attained with any 50mm lens.

Big-Koi

I have a Foroga M42-M4.3 adapter that is almost an inch thick. I am correct in assuming that should allow me to attain 1:1 images?
Thank you for your quick response

RWR Loc: La Mesa, CA

No. The adapter should be about 26.46mm long, which allows the lens to focus at infinity. You’ll need to add 50mm extension to that to attain 1:1. The lens itself will focus closer from infinity, but I don’t know how much extension that adds - a few mm at most.

Apaflo Loc: Anchorage, Alaska

Perhaps it should be mentioned that while a 50mm lens can be focused close enough for a 1:1 reproduction ratio there are distinct disadvantages in doing so that generally will mean 50mm focal length is not normally used for that kind of macro work.

The working distance (front of the lens to the object) is very short. That means the angles for light rays can be quite high, causing refraction error and less sharp images. It can be very difficult to illuminate a subject without shadows from the lens. And moving a lens that close to live subjects can cause insects to flee and rattlesnakes to bite.

Macro lenses from 40mm to 85mm are usually used for closeups, as opposed to 1:1 macro work. They are great for flowers as an example. 90mm to perhaps 150mm are more commonly used for 1:1, while 200mm or more are typical at 1:1 reproduction when a greater working distance is necessary.

Big-Koi

I just checked, and closest I can get is 54 mm by adding two extension tube sections to the adapter.
I have a Pentax primary 55mm 1.8 lens, which is not a macro. Will that work and give me 1:1?
I will give it a try in the next few days.
By the way, how does one calculate to determine what is need to achieve 1:1 images?
Thanks again for your efforts,

Apaflo Loc: Anchorage, Alaska

The simple answer is to add extension tubes equal to the focal length.

That works for a "simple lens", and will be close for any lens. That will be true if the lens focus is set to infinity, where the built in extension will be equal to the focal length. Hence the total extension will be twice the focal length. But if the lens is set for minimum focus distance, either the reproduction ratio will be higher or one can use significantly less added extension.

With a 100mm lens it only takes 100mm of extra extension if the lens is set the infinity mark. If it is able to focus down to a 1:2 ratio without an extension tube, it might only take an added 50mm of extension to get a 1:1 ratio.

All of this is approximate because no real life camera lens is a "simple" lens, and what may have been a focal length of 100mm when focused at infinity is probably much different when focused closer.

If you want exactly 1:1 the best way is actually measure it. Put an extension tube between the camera and the lens, and shoot two images of a tape measure, one with the lens set at infinity and again at its closest focus setting. At 1:1 your image of tape will show exactly the same width as your sensor.

If the first image with infinity focus set is too much magification switch to a shorter extension tube. Or, if the short focus setting is too little switch to a longer tube. With a tube that has too much at the short setting and too little at the infinity setting the lens focusing adjustment can be, with not too much experimentation, set to as close to 1:1 as you care to measure it.

RWR Loc: La Mesa, CA

Flange Focal Distance (FFD) is explained here: http://en.wikipedia.org/wiki/Flange_focal_distance
Specific lens to camera adapters are typically designed for the lens to focus at infinity, with the lens itself set at infinity. M42 lens FFD is 45.46mm, M4/3 camera FFD is 19mm, so the adapter itself will be 26.46mm long. To attain 1:1, the lens needs to be extended by its focal length, so the adapter + extension will be 76.46mm. At 1:1, the lens flange to focal plane distance will be 95.46mm.