Silverrails wrote:
Is there a difference between a Micro Lens and a Macro lens? Please Explain.
Yes and no.
There is no generally-recognized authority that controls usage of these terms, so exact limits are not found. However, there are general areas where these terms can exist.
First, at a Leica class in the 1970’s I heard that general photography works on a range of capturing images of objects about the size of a sheet of typing paper or larger. Since this was Leica, and they were dealing with full frame 35 mm film, that meant photographing any object over 10 times the size of the film would be a normal photo. This would be areproduction ratio of 1:10, where the image is 1/10th life size.
They then classified closeup and macro photography as creating images in the range of 10:1 to 1:10 magnification on the film. Right in the middle of that would be 1:1 reproduction where the image on the film would be the same size as the original object. And 10:1 would give a magnified image on the film.
You should remember that Leitz, the company that makes Leicas (LeitzCameras) was in the business of making microscopes for many years before they got into cameras—and part of that included capturing pictures through their microscopes. So, of course they had a word to describe that: Photomicrography.
I had used my camera is high school biology to capture images thru the microscope, and at that time I referred to it as microphotography. I was wrong. That term is more properly used when dealing with the creation of small or very small images, such as microfilms, micro fiche, and those microdots that the spies are always using to smuggle out secret plans.
There is also telephotography where one photographs images (like stars) through a telescope.
These 4 different areas of photography use distinctly different types of optics. Formulas that work for telescopes might not be the best for microscopes, or camera lenses. But all obey (pretty much) the same laws of optical physics.
Hopefully you have followed this so far, because things have changed, or maybe they were never so simple.
It seems (almost) nobody really gives a damn about how big the negatives are. They really care about how good the prints are.
With current digital cameras you have a wide choice of sensor sizes, from cell phones to copy machines. Now my copier should give me an 8.5x11” copy at 100% the same size as my 8.5x11” original. A 1:1 ratio. I’d call that “macro”, and get few arguments. But if I can feed an image captured on my cell phone through my computer and print it out at the exact same size—can I call that macro?
A similar question came up in the mid 1970s when computers came into the design of complicated zoom lenses. The first zoom lenses did not focus to near distances, largely for mechanical reasons. Adding shifting lens elements changed that, but those elements had to move precisely, and computers did the math and designed the mounts and internal cams in months. Doing the calculations by hand for the earliest zooms took a year to over a decade.
The advertising for ‘New’ macro-zooms in the mid 70s seemed to hover around lenses which could focus close enough to fill the negative at a 1:4 ratio. So, an object 4”x6” would fit on that 1x1.5” film. But nobody really cared about the film size except slide photographers. People got 4x6 prints and what they saw on those was as big as their original—so why not call it ‘macro’?
Actually, the people doing 35mm slides were projecting them on 40” wide screens, so little bugs were wall-sized monsters! Macro could be scary.
Optic design comes into play. Commercially, the most common 1:1 image capturing involves copying a flat object onto a flat print. A Xerox copier does that. So does a process camera.
For these operations you need a lens which is sharp and is corrected to produce a flat image field. So, lenses for large-format process photography that might be used to create halftone images for photoengraving were the basis for the design of lenses used to copy 35 mm slides, and other photos taken at close distances, and ‘true macro’ lenses were designed for flat field at 1:1 reproduction ratios.
Your conventional camera lens is a compound item with 3 to 20 or more elements. Consider, however, a simple lens which is just one element. When that simple lens is focused at infinity the center of the image will be in focus. The distance from the optical center of the lens to the in-focus image is the focal length of the lens.
As you move away from the center, towards the corners of film or focusing screen, the image is no longer in perfect focus on the flat film or screen. The points where the image is in focus are in front of the screen. It is geometry. You would need to capture your image on the inside of a sphere with the same radius as the focal length of your simple lens to get it to focus anywhere but dead center. So, to give a flat field at infinity, additional pieces of glass are ground to change the path of the light and allow a 3 dimensional world to get into focus on a 2dimensional plane.
Now, if perfect correction is designed for infinity, focusing on closer objects will not be as good—and the closer you focus the worse it gets. The good news , however, is that modern lenses do a really good job, and depth of field from smaller apertures helps.
Projection lenses, such as those on slide projectors, are designed for flat fields at 20 to 30 magnifications. Movie theater projection lenses are designed for larger distances. Lenses for enlarging negatives are designed for flat fields at close distances and are great(optically) for close-up photography. As film photography has dwindled lots of these lenses are available at a fraction of their value. The problem is they rarely have focusing mounts so they need to be used on bellows. Also, their diaphragm has no linkage to a camera so exposure metering and operation is slower and much less convenient.
Nikon calls their line of lenses ’Micro’. Some people think this may a typo or a bad translation of Japanese into Greek. Personally, I think it has to do with the usefulness of the lens in the creation of small images in microphotography. Such work would include making microfilms by copying paperwork ranging from typing paper to newspaper pages. A lens designed for this would need exceptional resolution and a flat field—as these lenses do.
Some people say a macro lens must focus to 1:1 or lifesize. I have found this criteria to be an exception rather than the rule, particularly if the lens is mounted in a metal barrel. More often they are made to be mounted on a bellows or used with extension rings. This is more to do with the mechanics of how the lens is mounted than its optical properties.
A lens must be located so its optical center is twice its focal length from the image at 1:1. At infinity it must be its own focal length from the image. For a 50 mm lens it would need 50 additional mm pf extension to focus from infinity to 1:1. For a 100mm macro it would need to go from 100 mm to 200 mm, and so on. Can this be done? Sure. But it affects lens use for general purpose photography.
Generally you’ll find the near-focus distance for SLR lenses to be about 10 times the focal length. To get that with a prime lens requires an extension of 1/10 the focal length. With a 50 mm lens that is 5mm of movement, and typically you go from one end of the scale to the other in a half revolution of the focusing ring. To get to 1:1 would require another 45 mm of extension, or 9 times the twisting.
Hope this helps.