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Why do macro lenses have ratios?
Macro lenses always have a ratio associated with them. Apparently it has to do with a magnification factor. Why do they have a magnification factor? Why not just have 1:1?..

Comments (11)

It takes a fairly long focal length + fairly close-focusing to get to 1:1. Might be noted that if you're very close, lighting the subject well enough that you still can get a decent exposure when stopped way down (for the increased DoF) becomes an issue all by itself, for subjects that move anyway..

Granted, there are lenses which do better than 1:1 the Canon 65mm MP-E uses internal bellows to get you to 5:1 lifesize..

Might also be noted that the magnification ratio alone perhaps is less meaningful for digital than film, since there are differences in resolution even for the same sensor size (and even in 'real' terms taking into account noise and all particularly if you compare across generations)...

Comment #1

Joshpa1980 wrote:.

Macro lenses always have a ratio associated with them. Apparently ithas to do with a magnification factor. Why do they have amagnification factor? Why not just have 1:1?.

I dont think I follow, but it is because it also has to do with a subject distance, so to speak..

1:1 means that the lens will focus close enough so the object is real life size on the film, so to speak. If 1/2 inch tall in real life, the image will be 1/2 inch tall on the film too. Today it means the same thing on the digital sensor, which is a harder concept because we cannot take it out and develop it and look at it, but nevertheless, that is what it means. The sensor or film can be any size, but 1:1 means the object is exact life size (in inches or mm) on that sensor. We can see the digital image made from it, but this size depends on the print enlargement too..

The lens shows focus subject distance in feet/inches too, but this varies with lens focal length, so it has no real meaning to size, not without stating a lot of other things too. Instead, the macro lens also shows ratio of size to original size..

Anyway, if 1:1 is too large in your viewfinder for your goal, then you back off a little distance, to 1:2, or 1:10, or whatever. Any regular lens at it's closest focus distance has such a ratio too... normally in the specs, often maybe 1:6, or thereabouts. A lens with "macro focusing" might to to 1:3. A true macro lens goes to 1:1. 1:1 means that it focuses much closer, to create a larger image...

Comment #2

Joshpa1980 wrote:.

Macro lenses always have a ratio associated with them. Apparently ithas to do with a magnification factor. Why do they have amagnification factor? Why not just have 1:1?.

That is the maximum magnification. It is often stated as a decimal. 1:1 is 1.0, 1:2 is 0.5, 1:6 is 0.16, etc..

Some macro lenses state 1:1 because that's their maximum magnification. Not all macro lenses are 1:1..

Seen in a fortune cookie:Fear is the darkroom where negatives are developed..

Comment #3

Thanks for the responses guys! "Unfortunately", I have more questions .

(1) Do you only need a 1:1 if you want to get really close? What if I want to take a photograph someone's face where their face fills the entire frame, would a 1:1 be suitable for this? Or is a 1:1 better suited for something like an ant?.

(2) Does anyone have any photos that show what types of shots you'd shoot with a 1:1 ratio?.

(3) Can an extension tube make a lens that doesn't have a 1:1 ratio into a 1:1 ratio?.

(4) How exactly does (for example) a 100mm 1:1 and 50mm 1:1 each make an object that is 1/2 inch in real life look 1/2 inch on film? I would think that the 100mm lens would have a greater magnification...

Comment #4

To try and help..

Joshpa1980 wrote:.

Thanks for the responses guys! "Unfortunately", I have morequestions .

(1) Do you only need a 1:1 if you want to get really close? What ifI want to take a photograph someone's face where their face fills theentire frame, would a 1:1 be suitable for this? Or is a 1:1 bettersuited for something like an ant?.

Yes 1:1 is for getting close, for making a final image that is larger than life..

1:1 for the ant, yes..

If you took a picture of someones face at 1:1 on a consumer DSLR you would capture an area about the size of a persons eyeball, if you were shooting 35mm film you would capture their eyelashes as well. If you took a picture of a penny at 1:1, the image of that penny projected onto the sensor or film would be exactley the same size as the penny..

A head shot would perhaps be in the ball park of 1:25 - 1:45 (film:subject). (just a stab I didn't do the math)..

(2) Does anyone have any photos that show what types of shots you'dshoot with a 1:1 ratio?.

Sorry not online..

Http://en.wikipedia.org/wiki/Macro_photography.

Http://www.kevinwilley.com/l3_topic05.htm (fromprobably answers many of your questions).

There are plenty of examples and information available through Google..

(3) Can an extension tube make a lens that doesn't have a 1:1 ratiointo a 1:1 ratio?.

Yes, bellows can also be used..

(4) How exactly does (for example) a 100mm 1:1 and 50mm 1:1 each makean object that is 1/2 inch in real life look 1/2 inch on film? Iwould think that the 100mm lens would have a greater magnification..

It does but it uses the magnification to increase the working distance to the subject. You will be able to set up further away with the 100mm..

Hope that helps some..

Comment #5

Joshpa1980 wrote:.

Thanks for the responses guys! "Unfortunately", I have morequestions .

(1) Do you only need a 1:1 if you want to get really close? What ifI want to take a photograph someone's face where their face fills theentire frame, would a 1:1 be suitable for this? Or is a 1:1 bettersuited for something like an ant?.

1:1 is the maximum magnification but almost all macro lenses can be used at any distance just like a normal lens..

(2) Does anyone have any photos that show what types of shots you'dshoot with a 1:1 ratio?.

I think this is probably close to 1:1, maybe a little less..

Image control:Zoom outZoom 100%Zoom inExpand AllOpen in new window.

(3) Can an extension tube make a lens that doesn't have a 1:1 ratiointo a 1:1 ratio?.

Yes, but you are making the lens do something it wasn't designed for so you may get distortions and aberrations..

(4) How exactly does (for example) a 100mm 1:1 and 50mm 1:1 each makean object that is 1/2 inch in real life look 1/2 inch on film? Iwould think that the 100mm lens would have a greater magnification..

Magnification is a function of focal length and distance. The 100 mm lens achieves 1:1 from further away, and that is a definite advantage when photographing bees .

This is just the same as filling the frame in normal, non-macro photography of course. The 100 mm lens will fill the frame with a particular subject from twice as far away as the 50 mm lens...

Comment #6

Joshpa1980 wrote:.

(1) Do you only need a 1:1 if you want to get really close? What ifI want to take a photograph someone's face where their face fills theentire frame, would a 1:1 be suitable for this? Or is a 1:1 bettersuited for something like an ant?.

1:1 says that it can focus close enough so that a subject the size of the sensor can fill the frame. Some sensor sizes:.

35mm: 36x24mmAPS-C: a little smaller than 24x16mm4/3rds: 18x13.5mm.

I'd suggest with any of these sensor sizes, at 1:1 an ant would be be a bit too small and a face a bit too large..

1:1 is not a limit, BTW. I've gone to 4:1, so that an item roughly 4x6mm filled the frame of my APS-C DSLR..

(2) Does anyone have any photos that show what types of shots you'dshoot with a 1:1 ratio?.

The whole point is that 1:1 is the maximum ratio. The minimum for most lenses, assuming you can focus on infinity (which you normally can) is 1:~. You can shooting anything down to 1:1, but you can also do 1:2, 1:5, etc..

I prefer to think in decimals. 4:1 is 4. The thing I'm shooting is showing up on the sensor 4x the size it is in real life. Similarly, 1:1 is 1. The thing I'm shooting is showing up on the sensor at life size. A few more....

1:5 is 0.2, so I'm shooting something that is 120x80mm and it is filling up the 24x16mm frame..

1:~ is as close to 0 as you can get without being 0. I'm shooting R Doradus, the biggest star we know of. It is 515,000,000,000,000mm in diameter. Yet it doesn't come close to filling the frame, it occupies only a few pixels..

(3) Can an extension tube make a lens that doesn't have a 1:1 ratiointo a 1:1 ratio?.

Yes. You need the same extension as the focal length of the lens. Obviously this works better for shorter focal lengths, but not too short. With macro there's the concept of working distance. That is, the distance from the front element to the subject. For each mm of extension, you lose working distance in two ways:.

1. extension shortens minimum focus distance, that's how it ups magnification.2. extension lengthens the lens..

The two combined effects could easily give you negative working distance, i.e. plane of focus is somewhere inside the lens..

You can use teleconverters in macro. They up the magnification by the same multiple that they change the focal length, but working distance is unaffected. What does a 1.4x TC do to, say, a 1:3 lens? You can see why I like decimals. 1.4 x 0.33 = 0.46..

(4) How exactly does (for example) a 100mm 1:1 and 50mm 1:1 each makean object that is 1/2 inch in real life look 1/2 inch on film? Iwould think that the 100mm lens would have a greater magnification..

Depends on how closely they focus. In the example, the 50mm would be focusing closer, and have a shorter working distance. Shorter working distance isn't so good for lighting (lens shadow gets in the way), or for shooting killer bees..

Seen in a fortune cookie:Fear is the darkroom where negatives are developed..

Comment #7

Thanks alot guys. Your answers have really helped to demystify the "macro" lens for me..

So, although I think those 1:1 closeup shots are pretty cool, for my budget and interests I don't plan on getting quite that close to need 1:1. But, what about closeup shots of large fall leaves (like a Maple leaf) or a persons face. Would it still be preferable to use a macro lens (one that has a higher ratio than 1:1) verses using something like my 18-55 kit lens?..

Comment #8

Joshpa1980 wrote:.

But, what about closeup shots of large fall leaves (like aMaple leaf) or a persons face. Would it be still preferable to use amacro lens (one that has a higher ratio than 1:1) verses usingsomething like my 18-55 kit lens?.

Your 18-55mm lens has a max magnification of around 0.25 (i.e. 1:4). That's enough to capture a subject 96x64mm. A maple leaf or a person's face should be no problem..

For a person's face I'd use 55mm, as if you shoot with a shorter focal length that will force you to get too close and the perspective distortion will not be pleasing (nose will look too big, cheeks too fat, etc). Ideally for head shots on an APS-C camera a focal length of around 80 to 100m is about right..

Seen in a fortune cookie:Fear is the darkroom where negatives are developed..

Comment #9

Nickleback, how do you know that the 18-55 lens has a maximum magnification of .25? Is that at 18mm or at 55mm? I'm confused.  .

Nickleback wrote:.

Your 18-55mm lens has a max magnification of around 0.25 (i.e. 1:4).That's enough to capture a subject 96x64mm. A maple leaf or aperson's face should be no problem...

Comment #10

Joshpa1980 wrote:.

Nickleback, how do you know that the 18-55 lens has a maximummagnification of .25?.

Http://www.canon.com/...m/camera/lens/ef/data/ef-s/ef_s18~55_35~56ii_usm.html.

Plus two technical reports (for USM and USM II versions of the lens).

Http://www.canon.com/camera-museum/tech/report/200401/200401.htmlhttp://www.canon.com/camera-museum/tech/report/200505/200505-02.html.

I goofed. Maximum magnification is 0.28. That's around 1:3.5.

Is that at 18mm or at 55mm?.

55mm, states it in the first tech report link above. And usually it's at max focal length, but it depends on the lens..

Think of it this way. If you focus at 10 feet, with a 30mm lens you'll be able to capture a standing person. With a 300mm lens you'll be able to capture that person's eyes and nose. You are getting greater magnification with the longer focal length. With a zoom lens, minimum focus distance is typically the same throughout the focal length range. So if you are at minimum focus distance (for max magnification), you'll get greater magnification at the longest focal length..

I'm confused.  .

I hope I helped..

Seen in a fortune cookie:Fear is the darkroom where negatives are developed..

Comment #11

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