Does macro lenses of different focal lengths give the same image?

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RAKAMRAK

Aug 30, 2011
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#1
Let me explain my question a bit further. I have seen/used only two macro lenses till date Canon 100mm L and sigma 150mm OS. That also at a distance of more than 1 year. So I had no opportunity to test this question of mine.

What I am asking is, let's say I am photographing a small flower (pretty small) which is not going to occupy the entire image at 1:1 (let's say on a full frame camera). Now if I use different macro lenses - 50mm (Canon), [60mm (Tamron or Canon)-APS-C only], 70mm (Sigma), 90mm (Tamron), 100mm (Canon), 105mm (Sigma), 150mm (Sigma) or 180mm (Canon/Sigma/Tamron) - at 1:1 magnification focusing distance (varying the distance between the flower and my camera, of course) would I get the same image (not talking about sharpness here)? Probably this may be framed slightly differently, what is the importance and significance of the angle of view of different macro lenses at their minimum (or comparable magnification) focusing distances?

In case any of you have used more than one lenses at the same time you may have some idea about this. Any comment will be highly appreciated. Even better is if any of you have images like this to demonstrate the difference/similarities.
 
#2
If a macro lens gives 1:1 magnification (note the 50mm Canon does not) the the image size will be the same despite the different focal lengths, what changes is the minimum focus distance from your sensor to the subject.
As a general rule of thumb the longer macro lenses are better for subjects that my fly/run off, for static/inanimate subjects then the focal length is more down to personal preference/price.
 
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#3
Right, at 1:1 the same object will occupy exactly the same area of the image. Till this my understanding is clear. But ten things get a bit fuzzy for me.

Do you mean that the focal length difference of macro lenses have no effect on the 'image' (for example from the point of view of perspective) at 1:1 magnification other than the usability (that is subject to lens front distance while capturing the photogrpah)?
 
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#4
I have not really noticed a difference in perspective at 1:1, though I believe to longer lenses will give a shallower depth of field at 1:1 - I am not an expert here.
Note the minimum focus distance is measured from the sensor/film - this is indicated on the top of your camera by a circle with a line through it. As the longer focal length lenses tend to be physically longer the front of the lens may not be that much further away, from the subject, than a shorter lens - but it all helps with skittish insects etc.
 
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#5
John thank you for the replies.
Correct, the distance is from the film/sensor (the phi type symbol). I was kind of brushing over those issues (the 50mm needs an extender type thing as well for 1:1).

You are quite right that it that longer macros will have shallower depth of field. But I am specifically looking info about perspective - no one talks about that - may be because it is not important as such. But still.....
 
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#6
I don't know, but I suspect, that the difference in perspective would be more noticeable at lower magnifications. I think it's time for a trip to the camera shop and have a play with a few lenses!
 
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#8
The subject, as you say, will be the same size in the different images.

The perspective will be different in the images, that is the apparent shape of an object will appear more rounded with a shorter focal length and flatter with a longer focal length. This effect of perspective is vastly reduced in macro shooting.

At the same aperture value the different images, if framed the same, will have the same dof.

The most apparent difference between the images will be the background, the longer the focal length the more blurred it will appear, though that is an optical illusion, things in the background will be much bigger and less "busy".
 
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#9
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#10
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#11
If all the lenses can go down to 1:1 magnification; the subject will have the same size in the frame if you shoot at minimum focusing distance. However, the background will change slightly ; moreover lenses having a longer focal length can give you two advantages:

i- better, creamy blur, BOKEH
ii- allow a longer working distance (distance between the front of the lens and subject)

(ii) can be important if you are shooting shy creatures (insects etc.) plus will give you more options on lighting.
 
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#12
The main difference I have noticed is working distance. This is distance from camera to object and the available depth of field. Longer focal length sure seems to have less depth of field.

The field of view also changes, or it sure seems like it. An object at 1:1 with a 100mm lens fills less of the viewfinder than the same object at 1:1 with a 150mm or 180mm lens.

I prefer the 150mm focal length for macro, given a choice between 100, 150 and 180.
 
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#13
danski0224 said:
The field of view also changes, or it sure seems like it. An object at 1:1 with a 100mm lens fills less of the viewfinder than the same object at 1:1 with a 150mm or 180mm lens.
Click to expand...

It is correct that the field of view changes, however the size of an object at the point of focus will be the same at 1:1. It is objects in the background that change. Brian over at The Digital Picture has an exellent example of this in his macro lens review: http://www.the-digital-picture.com/Canon-Lenses/Canon-Macro-Lens.aspx

Scroll down and look at the photos of the purple flower. They are taken at different focal lengths with the same magnification. As you can see the size of the flower is the same, however the background is quite different due to the narrow field of view of the longer focal length lenses.
 
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#14
The images will all be different. Whenever you change sensor size or focal length the results will change.

There is a difference between image framing on full-frame vs Crop. If you shoot the same lens on APS-C and full-frame, with the same image framing, you would shoot from further back with the APS-C camera and as a result you will have more depth-of-field.

If you shoot with two different focal lengths, at the same magnification on the same body then the longer focal length will show less of the background. This gives you more control of your image by being able to eliminate possible background distractions. This is very important in macro.
 
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#15
danski0224 said:
The main difference I have noticed is working distance. This is distance from camera to object and the available depth of field. Longer focal length sure seems to have less depth of field.

The field of view also changes, or it sure seems like it. An object at 1:1 with a 100mm lens fills less of the viewfinder than the same object at 1:1 with a 150mm or 180mm lens.

I prefer the 150mm focal length for macro, given a choice between 100, 150 and 180.
Click to expand...

I'm hoping Canon replaces their 180mm L Macro with a lighter (and-hopefully-not-more-expensive) 150mm f/2.8 IS Macro... and their 135mm f/2 with a 100mm f/1.4. That would make my year (of the lens).
 
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#16
Thank you CRians. So my hunch was more or less right that the background will be slightly different. But from your replies it seems that such difference won't really matter in most cases (in few cases it might though). What will matter mainly is the subject to front element distance - which is generally longer for longer FL macro lenses.

Anyway, day before yesterday I received my Sigma 150mm OS. Waiting for the weekend to explore its abilities at the local park.
 
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#17
At 1:1 most macro lenses don’t have the focal length given in the specification.
The Canon 100L for instance is at 1:1 a 75mm lens (source: http://www.photozone.de/canon_eos_ff/458-canon_100_28is_5d)
You need to know the real focal length for each lens to compare them.
Look at the minimum focus distance of each lens.
The Canon 100L has a minimum focus distance of 30cm
The Sigma 150mm OS has a minimum focus distance of 38cm
If you compare specified focal length the difference between the two is 50%
If you compare minimum focus distance the difference between the two is less than 30%
 
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#18
@100 Thanks for the link. But do you know any other source where I can get the 'effective focal length' information for the macros. The photozone website seems to have the information is only for the 100mm lenses. I will google it. But in case you know any other website please let me know. This is a very interesting piece of information.
 
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#19
A macro lens is nothing special. You will have the same type of differences with the small objects as you would have with a large objects, say, a building:
With a shorter focal length (macro but also non-macro) you will have to move closer (building with a 28mm lens) and with a longer focal length lens (building with a 200mm lens) you will have to back up, but you can fit the building on the sensor in either case. The perspective changes (for macro and for non-macro lenses alike), and you will get different DOF (for macro and for non-macro lenses alike).
If you just shoot flat subjects you won't notice any difference at all: A 2D test chart looks the same with a 600mm and a 14mm lens, a stamp will look the same with a 60mm or a 200mm macro lens. The difference only can be seen when you shoot 3D objects - huge buildings or tiny flowers.

But the biggest difference, for macro and for non-macro lenses alike, will be the greater distance from the subject, and this will make a huge difference with scary subjects and only a small difference with flowers.

Personally, I have the 100mm Canon macro and would really like a longer lens like the 180 Canon macro, because the working distance gets so immensly short at 1:1...
 
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#20
RAKAMRAK said:
@100 Thanks for the link. But do you know any other source where I can get the 'effective focal length' information for the macros. The photozone website seems to have the information is only for the 100mm lenses. I will google it. But in case you know any other website please let me know. This is a very interesting piece of information.
Click to expand...

I don’t know if this applies to every optical design but if you take the minimum focus distance in mm and dived that by 4 you get the effective focal length in mm.

The old EF 100mm f/2.8 USM macro has a minimum focus distance of 310mm => 310/4=78mm
The new EF 100mm f/2.8 USM L IS macro has a minimum focus distance of 300mm => 300/4=75mm
The Sigma 150mm f/2.8 Macro OS has a minimum focus distance of 380mm => 380/4=95mm
The EF 180mm f/3.5L has a minimum focus distance of 480mm => 480/4=120mm

The minimum focus distance is the distance from the subject to the sensor. The working distance however is from the front of the lens to the subject so you also need to consider the length of the lens and the flange distance (distance between the front of the lens mount and the sensor). The flange distance for EF-mount is 44mm.

The EF 100mm f/2.8 USM L is 123mm long. The minimum focus distance is 300mm. So the working distance is 300-123-44=133mm
The Sigma 150mm f/2.8 Macro OS is 150mm long. The minimum focus distance is 380mm. So the working distance is 380-150-44=196mm
The EF 180mm f/3.5L is 187mm long. The minimum focus distance is 480mm. So the working distance is 480-187-44=249mm.
 
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