What makes a macro lens a macro lens?

MDesigner · Jun 11, 2008

I'm a little confused about lenses that are advertised as macro lenses.. even though many lenses DO have the macro symbol printed on them along with a range (e.g. 0.9 feet). What exactly does 0.9 ft mean in this case? Is that the closest you can get to an object before it can't focus on it? What does macro mode on my EOS 40D actually do, from a technical standpoint, and how do I use macro mode in Av or Tv modes? (I'm pretty sure it has something to do with setting a certain focal length)

I'm looking at a Canon 60mm macro lens, and it says the closest focusing distance is 0.65 feet. Yet my old Nikon Coolpix 8700, far from DSLR, could do macro with a minimum distance of 3-4 inches or so.

How does this work?

asfixiate · Jun 11, 2008

Its the minimum distance you have to be from your subject in order to focus.

Generally people here use full manual with Macro.

60mm is good lense by the way.

im_trying11 · Jun 11, 2008

i was wondering the same thing i can get so much closer on my coolpix s7c

asfixiate · Jun 11, 2008

getting closer meaning zoom in closer or moving the camera closer?

the .65 means you can literally be .65 feet away from target and take a pic.

MDesigner · Jun 11, 2008

What I don't get is, why would this 60mm be called a "macro lens" and a 50mm not be called a macro lens? What is it about the 60mm that allows it to be referred to as a macro lens? And again, 0.65 ft doesn't sound too impressive to be honest... that's 7.8 inches away from your subject.

Also, another question: depending on what lens you get.. let's say your lens has a range such as 18-55mm. Which focal length do you need to be at to achieve that shortest shot distance?

asfixiate · Jun 11, 2008

why isn't 7.8 inches away not impressive? You need to get closer than that?

the below will resemble difference between macro and my zoom lense.

The minimum focus of my zoom lense is 14.6 feet.

Socrates · Jun 11, 2008

MDesigner said:
I'm a little confused about lenses that are advertised as macro lenses.. even though many lenses DO have the macro symbol printed on them along with a range (e.g. 0.9 feet). What exactly does 0.9 ft mean in this case? Is that the closest you can get to an object before it can't focus on it? What does macro mode on my EOS 40D actually do, from a technical standpoint, and how do I use macro mode in Av or Tv modes? (I'm pretty sure it has something to do with setting a certain focal length)

I'm looking at a Canon 60mm macro lens, and it says the closest focusing distance is 0.65 feet. Yet my old Nikon Coolpix 8700, far from DSLR, could do macro with a minimum distance of 3-4 inches or so.

How does this work?

The bottom line is the size of the image on the film/sensor.

There is a bit of disagreement regarding the correct definition. Purists maintain that a true macro will focus close enough to the subject so that the image of the subject on the film/sensor will be the same as the physical size of the subject. A picture of your thumbnail will cover half a 35mm frame and won't fit in a DX-sized frame!

I have a (now discontinued) Nikon 28-85 zoom with "macro" capability in the 50-85 range. I can get the image to be one-half of the physical size of the subject and that's fine for my purposes.

chris · Jun 11, 2008

A macro lens should be able to give 1:1 reproduction (ie lifesize) of the subject on the sensor or film in the camera. Sometimes this is achieved by using an extension tube. The best macro lenses (usually primes) are built to give their best performance at short subject distances and often have minimum apertures that are significantly smaller than for normal lenses.

Helen B · Jun 11, 2008

The convention for focus markings on interchangeable lenses is that the distance is measured from the image plane, not from the front of the lens. At 1:1 magnification (the limit of that Canon 60 mm lens when used on its own) the 'working distance' is less than 4 inches. That's the distance from the front of the lens to the object in focus. The distance from the image plane to the object in focus is 0.65 feet (7.8 inches).

As already mentioned, it is better to look at the maximum magnification that the lens can achieve, rather than the closest distance it can focus, because you may be dealing with lenses of different focal lengths etc.

Macro lenses are optimized for macro work - ie their optical formula is designed for the macro range. General purpose zoom lenses may be able to focus closely, but their image quality may not be very good.

Best,
Helen

julie32 · Jun 11, 2008

Back to one of the original questions here. If I have a 28-135 F2.8 lens and I want to shoot macro why can't I just zoom to 100 mm like the 100 mm macro lens and it be the same thing? Is it the glass that's actually different? Please explain why someone would want a 60mm versus a 100mm prime macro?
Thanks

Socrates · Jun 11, 2008

julie32 said:
Back to one of the original questions here. If I have a 28-135 F2.8 lens and I want to shoot macro why can't I just zoom to 100 mm like the 100 mm macro lens and it be the same thing? Is it the glass that's actually different? Please explain why someone would want a 60mm versus a 100mm prime macro?
Thanks

Be reminded that the desired end result is the size of the image relative to the actual physical size of the subject. (Read my previous post as well as the ones that followed from Chris and Helen B.) The focal lengths and focusing distances are nothing more than the means to achieve that end. There is nothing in your descriptions of lens choices that tells me the ratio of the image size to the actual subject size. Give me that information and you'll be able to answer the question yourself.

One thing that will not shout out to you is the possibility that a 100mm prime and a zoom set to 100mm will give the same size image. Then, you need to drop down to the next decision factor - which one produces better quality images? Almost without exception, the winner in that category will be the prime.

JimmyO · Jun 11, 2008

julie32 said:
Back to one of the original questions here. If I have a 28-135 F2.8 lens and I want to shoot macro why can't I just zoom to 100 mm like the 100 mm macro lens and it be the same thing? Is it the glass that's actually different? Please explain why someone would want a 60mm versus a 100mm prime macro?
Thanks

Becuase it can focus closer at that length... thus more magnification.

Socrates · Jun 11, 2008

JimmyO said:
Becuase it can focus closer at that length..,

You can't say that unless you know the focusing capabilities of the two specific lenses in question.

julie32 · Jun 11, 2008

I just rented the 100mm macro lens, it should arrive on Saturday. I am excited to play around with it and see what I can do. Renting is a great option. http://www.lensprotogo.com/ This is a wonderful resource. I got an email personally from the owner of the company and the lens was sent out 30 minutes after I ordered it.
Hope it helps someone else.

Garbz · Jun 11, 2008

Socrates said:
You can't say that unless you know the focusing capabilities of the two specific lenses in question.

You don't need to know the focusing capabilities. The 24-135 macro at 100mm will not focus as close as a prime 100mm macro. I've never seen a zoom that's come close to a prime macro capability wise. For the record 24-135 has a max ratio of 1:3.8 The 100mm macro 1:1 as expected of all prime macros worth getting. I'll retract my comment if you can show me a real practical lens (by that I mean not like Sigma's 1200mm f/2.8 because we can effort) that has a decent zoom range and is 1:1.

Btw on your earlier comment. How BIG are your hands! Your thumbnail doesn't fit on a DX sensor at 1:1 ????