'Macro' = 1:1 ?? What does this really mean

[Ldysic]

I have heard "a macro lens has 1:1 imaging". So I think that must mean that a 'macro' lens will photograph a ruler, at max magnification and good focus, to match the sensor size.

My Pentax Kx sensor is 23.6x15.8 mm. So that ruler picture should show no more than 23.6 mm of the ruler.

With my Tamron 18-200 Macro lens, the best I can do is 80.1 mm. That seems to say this is NOT a macro lens.

Do I have the wrong definition for the 1:1?

[ravncat]

You are correct.

Many manufacturers are using the term Macro to refer to "close focusing" such that a lens will focus within a foot or something. I`m not sure exactly what they use. Tamron is guilty of this.

It`s better to look at the reproduction ratio to really know how macro a "macro" is.

[RichardTaylor]

You have the "traditional" definition of a true macro.

Some manufacturers like to call their lenses "macro" howver they are not true macro.

Your lens is not a macro.
Check out the maximum magnification specs here.

Maxwell International Australia

.

[OsmosisStudios]

1:1 is fairly simply, and best explained with a frame of film.

Let's say you set up a wonderful shot of a dime (a 10¢ piece) with a macro lens set to 1:1. You take the shot on a roll of film, have it developed, etc.

If you place that frame of film next to the dime, the image of the dime and the dime itself will be the same size.

What it means is that you're reproducing your subject on the imaging plane (film or sensor) at the same size that it exists in real life.

This is the same on digital, and is NOT affected by crop factor. What it means is that of your subject is, say, 12mmx12mm in size in real life, it will occupy a space of 12mmx12mm on your sensor.

If you're using a lens with "macro" capabilities (as some off-brand zooms are labelled), you're not getting true 1:1 reproduction. Some offer 1:2 (half size) but most are 1:3 or less (third size). What this means is that a subject that is 12x12mm would be 6x6mm or 4x4mm, depending on the lens.

This depends on the lens. The 18-200 youre using like exhibits some close-focus breathing, which isnt helping issues.

[Elmo]

Some non-third party lens marked macro will not go 1:1 without adding extension tubes.

[wulf]

Originally Posted by OsmosisStudios

If you place that frame of film next to the dime, the image of the dime and the dime itself will be the same size.

Of course, you don't actually view the image on the sensor but on screen and so even an image shot at 2:1 or 3:1 gives you a much larger than life version of your subject to stare at. Your dime shot ends up looking like a million dollars (as long as you nailed the focus, coping with the extremely narrow depth of field!).

Even with film-based photography, you would typically display your images in the form of prints rather than at film-size. Therefore, "macro" has become conflated with "extreme close-up". Given that reproducing an item at life size on the sensor is a fairly arbitrary yard-stick, I think it is not unreasonable to use the broader definition as long as your photograph brings the viewer closer than they could easily see with the naked eye.

Wulf

[RichardTaylor]

I think it is unreasonable to use the marketing definition as it raises false expectations.

Seeing the words "macro" on a lens description makes me think I am going to get this when I use it.

(1) Shot at near or at minimum focussing distance with a 1:1 macro lens.


However I would get something like this using a "marketing" macro.
(2)


Look at the words (from Tamron's web site) re a "marketing" macro.
Tamron -55-200mm F/4-5.6(Model A15)

Quote
"closeups that rival macro lenses with a minimum focus distance of 0.95m with a ratio of 1:3.5."
End quote.

For their 1:1 Macro.
Tamron -60mm F/2(Model G005)
Quote
"top-notch macro shooting performance down to 1:1"
End quote

It's like getting paid. Do you want your full pay or something close, but less than, to it?

[wulf]

How does the definition cope with the ongoing increase in camera resolution? For example, my first digital camera (a Fujifilm 1400 FinePix Zoom) had a maximum resolution of 1260x960. My D40 can go up to 3008x2000 (and a little higher in RAW mode), so over twice as much detail and I know that is at the low end of what is available today.

Let's say your camera can produce an image twice the size of my D40. If I take a wonderfully close-up shot like the one above with a 1:1 macro, you could replicate it with a 1:2 lens and some cropping. Film is analogue, so a system that uses the measurement of real-life compared to size on the film makes sense. On a digital camera, what matters is not so much the size of the sensor but how much information that sensor can capture - always a compromise but increasingly one that is undiscernable until you zoom in extremely close.

You should definitely be aware of the capabilities of the lens you are getting but need to consider that in the context of the capabilities of your camera as well. A lower ratio with better quality glass and a high MP camera will probably yield more amazing close-ups than a 1:1 "true macro" lens with glass that tends to distort the light and blur the image.

Wulf

[OsmosisStudios]

wulf: my post referred to the film frame itself (as in the negative). At 1:1, the image on the negative and the subject will be the same size. That's the definition. While I agree it's fairly arbitrary and frivolous, it IS what the OP asked about.

[RichardTaylor]

Thanks for the nice words on my bug pic.

I agree glass does make a huge difference, if your technique is up to scratch.
Any poor IQ lens will not produce amazing results (unless you want the blurry "art" feel)

For myself if I want to just to shoot macros it will be my 100mm macro (minimum magnification 1.1) prime.