Macro 1:1 or not?

Jeff Spangle

Jeff Spangle

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I have recently entered a discussion with a friend regarding magnification from real macro lenses.

His argument relaes to the Sigma 105mm macro on a Nikon mount (on a D300) against the Micro-Nikkor 60mm macro.

Unless stated, I was under the impression that a true macro lens can go up to 1:1 only and to achieve a bigger image on the sensor would require reversing rings/bellows/tubes etc.

He claims he can focus at a closer distance (which is right) and then claims it's a bigger image using the Nikon compared to the Sigma.


Am I going mad?
 
True macro is at least 1:1 from memory - you can go bigger if you want.

It is all a balance between minimal working (focus) distance and focal length - most lens work out virtually the same but the longer lenses mean you don't have to scare the bugs quite as much

it may well be than the Nikon 60mm has a slightly better magnification but it won't be by much - certainly nothing a patch on the Canon MPE-65mm which goes up to 5:1!!!
 
Jeff Spangle said:
That is my understanding too.
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It may still work out slightly more magnified using the 60mm though.

Rough ball park maths:
the 105mm is 1.75times 'longer' than the 60mm.
If the minimum focus distance of the 105mm is more than 1.75 times that of the 60mm then the 60mm will allow you to get proportionally closer for the amount of zoom on your lens making the wee beastie bigger in proportion than it would appear with the 105mm.

I know this probably isn't the best of explanations nor the most technical but I can't think of another way to phrase it


The question is would the beastie remain still long enough for you to get in so close with the 60mm? Magnication at MFD is not the be all and end all
 
Uneducated_Rick said:
True macro is at least 1:1 from memory - you can go bigger if you want.

<snip>
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I've often wondered about this, and can't seem to find a definitive source to confirm that it's got to be 1:1; but it sure seems to be the norm.

What makes me question the 1:1 ratio as being a minimum requirement is the Zeiss Makro Planar, it only goes up to 1:2 ... and that's a lens to drool over.
 
Fair point Rick. He is photographing watches so there is no issue with movement. I just couldn't see the big difference if any between one macro 1:1 lens and another. What sparked it all off was a review he read on the Sigma which mentioned it wasn't that good in some areas (he feeds off online reviews) and as a result bought the Nikon. I would have bought the Tamron 90mm to be honest, but then I have one of these anyway :)
 
The 90mm is pin sharp, I'm really pleased with it. I hear so many stories regarding Sigma quality that I steer clear now.
 
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I've had a couple of Siggy primes and have never had an issue - the 150mm is absolutely revered as a macro lens

A lot of the talk about Sigmas is that - talk

Try a couple out, try the 30mm and 50mm f/1.4, and see if the Canons are worth the extra money
 
You maybe right for primes. I had a 28-70 f2.8 that had a bubble in an element, that got swapped and a friend has a 120-300 2.8, it took 3 copies to get a good one.
 
Jeff Spangle said:
I have recently entered a discussion with a friend regarding magnification from real macro lenses.

His argument relaes to the Sigma 105mm macro on a Nikon mount (on a D300) against the Micro-Nikkor 60mm macro.

Unless stated, I was under the impression that a true macro lens can go up to 1:1 only and to achieve a bigger image on the sensor would require reversing rings/bellows/tubes etc.

He claims he can focus at a closer distance (which is right) and then claims it's a bigger image using the Nikon compared to the Sigma.


Am I going mad?
Click to expand...

I don't know either of the lenses you are referring to, but my understanding of a 'true' macro lens is that it will produce an image at 1:1 or greater on a camera sensor which can be thought of in this way.... If you were to place a fly on the camera sensor and somehow be able to record that image! then that image would be life size. The focal length has nothing to do with the macro capability, only in the closest distance that you would be required to focus to achieve 1:1 . The longer the focal length, generally the further away you need to be.
 
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I'm selling bits and pieces on ebay to fund a macro, looking at the Sigma 70mm f2.8 maybe a better one, dont think i can afford a Nikon 150mm, got £110 so far, have a mountain bike & Sony PSP to sell yet, lol
 
There is no formal definition of a macro lens, other than it is one that is designed for very close working as its primary purpose. Generally speaking they are primes, and will go down to 1:1 without any accessories, but there are exceptions.

1:1 delivers a life-size image on the sensor. The subject distance, focal length and framing may vary, but 1:1 is always the same.
 
Splog said:
I don't know either of the lenses you are referring to, but my understanding of a 'true' macro lens is that it will produce an image at 1:1 or greater on a camera sensor which can be thought of in this way.... If you were to place a fly on the camera sensor and somehow be able to record that image! then that image would be life size. The focal length has nothing to do with the macro capability, only in the closest distance that you would be required to focus to achieve 1:1 . The longer the focal length, generally the further away you need to be.
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That is my understanding too, thanks for confirming.

I can't see as there can be much difference in magnification between the two lenses. Personally, I would always go for the longer focal length to give greater working distance so as not to disturb the subject (if wildlife) and not to cast a shadow.


Does anyone use bellows/reversing rings/tubes?
 
In the table below you can see that the minimum focus distances (MFD) for various lens changes but the magnification is still 1:1 at MFD. If your mate thinks he's getting more magnification get him to take a picture of a rule at maximum magnification, at 1:1 he Will see 23.6mm (the width of the sensor in a D300) anything less than 23.6mm and he's getting more magnification, there might be a slight variance of a couple of mm's between lens due to actual magnification ratio against stated.

focusdistance.jpg
 
1:1 is the same irrespective of the lens' focal length, which just determines the working distance. Dogfish's table shows that even this can vary depending on the lens (see the MFDs for the three 180mm lenses) which is related to how the optical system within the lens creates that magnification. Some lenses use internal extension of the elements (much like extension tubes) hence there is light loss as you move to 1:1 and some use optics and some use a combination of both. My Siggy 180mm loses about 1 2/3 stop of light at 1:1 rather than the usual 2 stops because the internal optics provide the additional magnification without further extension.
 
That's brilliant Dogfish, do you have the figures for the Nikon 60mm for comparison?
 
Brachytron said:
1:1 is the same irrespective of the lens' focal length, which just determines the working distance. Dogfish's table shows that even this can vary depending on the lens (see the MFDs for the three 180mm lenses) which is related to how the optical system within the lens creates that magnification. Some lenses use internal extension of the elements (much like extension tubes) hence there is light loss as you move to 1:1 and some use optics and some use a combination of both. My Siggy 180mm loses about 1 2/3 stop of light at 1:1 rather than the usual 2 stops because the internal optics provide the additional magnification without further extension.
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As an aside, what is happening is interesting optically. In theory, if you go from infinity to 1:1, you must lose two stops exactly of light, but the internal workings of some lenses means that they also change focal length as you focus closer.

While you still lose two stops, as the focal length reduces so the maximum aperture effectively increases (f/number gets lower) and the net result is that you appear to lose less light.

In the table above, some manufacturers might be accused of a slight of hand there, in that the main reason people buy longer focal length macros is to get a longer working distance. But that doesn't always fit pro-rata with the marked focal length, becuase the focal length changes!
 
A "macro" lens is simply one that has been optically corrected (Shape of the DoF and radial distortion, iirc) for close focusing, and there is no link what so ever between the term "macro" and what magnification it should achieve, as Hoppy said.
 
Woodsy said:
A "macro" lens is simply one that has been optically corrected (Shape of the DoF and radial distortion, iirc) for close focusing, and there is no link what so ever between the term "macro" and what magnification it should achieve, as Hoppy said.
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Thank you for clarifying that. May I ask, what is meant by "shape of DoF"; and what is "radial distortion"? :)
 
Please note, I'm not 100% sure this is correct, only 99%... but:

As we know, the DoF is the distance in front of, and behind the point of focus when objects appear in focus. Now, assume that the effect is in fact not gradual, and instead is a flat and distinct boundary... as if you had two pieces of paper held upright, and parallel to each other, and changing the DoF is analogous to moving these pieces of paper apart. It is widely assumed, and to an extend correctly so, as we never really see the effect, that the DoF boundary is flat. However it turns out it is not, and is in fact very slightly curved. One way of describing it would be to look at a sand glass timer side on, except with far less obvious curvature.

We of course never see this effect, as in most lenses is not very apparent, and indeed, even if you take a photo of a flat wall, there is still a flat plane at the point of focus meaning all the wall would be in focus anyway.

So, in a 'macro' lens, this shape has been corrected such that it is flat. The reason being, quite simply, that with such narrow DoF and close working distance of most 1:1 reproduction lenses, there then exists possible situations where the curved shape of the DoF might show in the photo.

I believe in the correction of this, the radial distortion (which I think is a poncy name for the same type of perspective correction ultra wide angle lenses have applied to them to remove the fisheye effect) (see here, http://www.isprs.org/proceedings/XXXVII/congress/5_pdf/29.pdf figure 3 and 4) is reduced also, meaning simply that 'macro' photographs appear more natural, in the same way portraits tend to look better with a long lens than a short.

I'll have a further look into this, as I'm still that 1% off in my head about the above. HTH anyway :)
 
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A true macro lens, that is one which has been primarily designed for close distance working, will differ from a more normal lens in that it will have very good field flatness (which Woodsy is talking about), good geometry or 'drawing' and be pretty sharp all over the frame at low f/numbers.

The natural tendency of a lens is for the plane of focus to be slightly curved. Normally this doesn't matter in the least but if you are trying to photograph a postage stamp for example, and your depth of field is very shallow anyway, then you need every mm of that shallow zone of sharpness to be where you want it, ie over the flat surface of the stamp. (This is also the reason why shooting flat lens resolution test charts at close distance, which is often done, usually gives a false indication of potential edge sharpness).

You also want this stamp, which is presumably rectangular with straight edges, to be reproduced that way, ie you don't want the edges curved with barrel distortion. That's good drawing, and incidentally enlarging lenses are also very good at this sort of thing too and they make good macros stuck on the end of a set of bellows for example.

And taking the stamp example again, you obviously want that absolutely sharp all over, right to the corners, even at lowest f/number where edge definition is always weakest. Normal lenses are not so good at this, being corrected for optimum performance at longer shooting distances.

If you look at these characteristcs and then relate them to how many people shoot macro, such as a bug or a bee or a small flower, it becomes clear that a pukka macro lens is not always necessary. And it explains why some cheap/simple accessories work so well, like the Raynox DCR-250 macro adapter for forty quid.

For example, a bee is 3D, not flat, and little bit of distortion doesn't matter in the least. Furthermore, the main subject is usually in the middle, so edge sharpness is less critical especially with shallow DoF when three quarters of the frame is out of focus anyway. And also because of the shallow DoF, to get as much of it as you can you tend to shoot at higher f/numbers which is where regular lenses tend to perform at their best, the sweet spot. However, turn that simple Raynox (basically a very strong supplementary close-up lens) on to a stamp or a coin or a watch face maybe, and the shortcomings will start to show.
 
Jonathan / Richard,

Thank you, both, for the input here. As always, very clear and helpful :thumbs:
 
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