What makes macro unique?

[z-lite]

I was going through my XTi literature and I was reading the small pamphlet about Macro lenses. Taking a look at the difference between the 60mm 2.8 USM and 50mm 1.4 USM, it seems that the macro lenses have much more narrow FOV, shorter focusing distance, and the 60mm has manual focusing but if it has USM, shouldn't it have auto-focusing or does the USM offer magnetic force for smoother manual focusing rather than a "geared"/mechanical focusing.

[gasrocks]

Macro lenses have to cover a wider range of distances, therefore, they usually AF slower. They are also better optically. The less DOF doesn't come from the lens itself but from the close working distance.

[Wilt]

'macro' generally refers to a 'closer focusing lens which permits you to obtain 1:2 reproduction on film/sensor'. Many lenses claim 'macro' but are merely 'close focusing' lenses. True macro lenses are optimized to perform better at close distances than an ordinary lens would; and true macro lens are typically 'flat field corrected' for reproduction of flat documents.

[z-lite]

Any input as far as the manual USM on the 60mm 2.8 is concerned?

[Mark_Cohran]

If it has USM it will auto focus. All can EF and EF-S lense are autofocus and manual focus capable.

[ben_r_]

The fact that you can make the physical life size of a subject project on the sensor at the exact same size (1:1 ratio) makes them pretty special.

[Mark_Cohran]

Additionally, USM lense have Autofocus with Full Time Manual override capability, i.e. you can focus in auto and touch up with the manual focus ring without having to shift the lens to manual focus.

[z-lite]

That is pretty sweet.Additionally, USM lense have Autofocus with Full Time Manual override capability, i.e. you can focus in auto and touch up with the manual focus ring without having to shift the lens to manual focus.
Thanks for all the info

[xarqi]

Additionally, USM lense have Autofocus with Full Time Manual override capability, i.e. you can focus in auto and touch up with the manual focus ring without having to shift the lens to manual focus.

Is it not only the ring motor USM lenses that offer FTM focusing? I thought micro-motor USM did not. Anyone able to confirm or correct this for me?

[Jman13]

None of the micro USM motors have full time manual except for the 50 f/1.4 which has FTM and a micro USM motor.

[xarqi]

None of the micro USM motors have full time manual except for the 50 f/1.4 which has FTM and a micro USM motor.

Super, thanks.

[Canon Bob]

.....The less DOF doesn't come from the lens itself but from the close working distance.

Actually the DOF is simply related to aperture and magnification and not working distance.

Bob

[xarqi]

Actually the DOF is simply related to aperture and magnification and not working distance.

Bob
But magnification depends on focal length and working distance, so everyone is right! ;)

[Canon Bob]

But magnification depends on focal length and working distance, so everyone is right! ;)

The 180L and the 100macro both have the same native maximum magnification. The working distance is very different but this doesn't affect the DOF.

Bob

[philthejuggler]

The 180L and the 100macro both have the same native maximum magnification. The working distance is very different but this doesn't affect the DOF.

Bob

I understood that it did affect the dof, or at least the degree of background blur. This is demonstrated here:

http://www.the-digital-picture.com/Reviews/Canon-EF-180mm-f-3.5-L-USM-Macro-Lens-Review.aspx

See 'background blur comparison' halfway down page.

Phil

[Jman13]

Right, but in that comparison, he even says the DOF is the same...the blur is smoother because less of the background is in the frame at the longer focal lengths.

[Canon Bob]

I understood that it did affect the dof, or at least the degree of background blur. This is demonstrated here:

http://www.the-digital-picture.com/Reviews/Canon-EF-180mm-f-3.5-L-USM-Macro-Lens-Review.aspx

See 'background blur comparison' halfway down page.

Phil

Phil..I think you're making a slight error in interpretation here.
Try this for a better explanation http://www.cambridgeincolour.com/tutorials/depth-of-field.htm

Note that I did not mention focal length as influencing depth of field. Even though telephoto lenses appear to create a much shallower depth of field, this is mainly because they are often used to make the subject appear bigger when one is unable to get closer. If the subject occupies the same fraction of the viewfinder (constant magnification) for both a wide angle and a telephoto lens, the total depth of field is virtually* constant with focal length!

I made the same assumption as you have a while back and got pulled up on it by someone. It set me off trying to prove my theory and ended up learning many things...including the fact that I was wrong !

Bob

[Wilt]

I understood that it did affect the dof, or at least the degree of background blur. This is demonstrated here:

http://www.the-digital-picture.com/Reviews/Canon-EF-180mm-f-3.5-L-USM-Macro-Lens-Review.aspx

See 'background blur comparison' halfway down page.

Phil


The show-me-state (Missouri) proof...

100mm lens f/11, at 12" away has DOF of 0.0869'

160mm lens f/11, at 19.2" away has DOF of 0.0869'

160mm lens f/11, at 12" away has DOF of 0.259'

a 63mm lens f/11, at 12" away has DOF of 0.0240'

[JeffreyG]

The show-me-state (Missouri) proof...

100mm lens f/11, at 12" away has DOF of 0.0869'

160mm lens f/11, at 19.2" away has DOF of 0.0869'

160mm lens f/11, at 12" away has DOF of 0.259'

a 63mm lens f/11, at 12" away has DOF of 0.0240'

What calculations are you using Wilt? Standard DOF tables (calculations) fall apart below 1:2 magnification.

[xarqi]

The 180L and the 100macro both have the same native maximum magnification. The working distance is very different but this doesn't affect the DOF.

Bob

OK - if you say it is so, I believe you - but I don't understand it. Something to add to my list of "things to get to the bottom of one day". Thanks for the heads-up on my misconception.

[DAMphyne]

Actually the DOF is simply related to aperture and magnification and not working distance
Somebody please explain this to me.
DoF is controlled by aperture, focal length, and subject distance in all the books I've read.
Is this like, special relativity for optics?

[Wilt]

What calculations are you using Wilt? Standard DOF tables (calculations) fall apart below 1:2 magnification.


I used f/calc, but I only assumed its calculations were correct and it was the only thing I had access to at the time. Using a different DOF calculator, it calculates 2.63mm DOF using CoC of 0.019, or 0.0862' or not very different than what f/calc provides. Furthermore, looking up in a reference book, at 0.5x using a CoC of 0.03mm the DOF is 3mm, so all results are in the same ballpark!

[Wilt]

Somebody please explain this to me.
DoF is controlled by aperture, focal length, and subject distance in all the books I've read.
Is this like, special relativity for optics?

Yes, only magnification and aperture are determinants of DOF in close-up photography. With longer FL, the falloff from optimal focus is more rapid than the rate of falloff with shorter FL.

Subject distance is FIXED for a specific magnification (reproduction scale) with a specific FL

[DAMphyne]

I gotta get a macro lens.
How would my 100/F2 lens work with extension tubes? Would I be able to get 1to1 with my 10D?

[Naturalist]

A true macro lens will go 1:1 without extension tubes. I have a EF-S 60 Macro and it is SWEET!

[Canon Bob]

I gotta get a macro lens.
How would my 100/F2 lens work with extension tubes? Would I be able to get 1to1 with my 10D?

It's very unlikely....

The native mag is only 0.14x at the lens' minimum focus distance. You can pop this up to 0.42x by adding a 25mm extension tube but it's probably that the minimum focus distance will get close to, or even end up within, the lens before you achieve 1:1.

Bob

[philthejuggler]

Phil..I think you're making a slight error in interpretation here.
Try this for a better explanation http://www.cambridgeincolour.com/tutorials/depth-of-field.htm

Note that I did not mention focal length as influencing depth of field. Even though telephoto lenses appear to create a much shallower depth of field, this is mainly because they are often used to make the subject appear bigger when one is unable to get closer. If the subject occupies the same fraction of the viewfinder (constant magnification) for both a wide angle and a telephoto lens, the total depth of field is virtually* constant with focal length!

I made the same assumption as you have a while back and got pulled up on it by someone. It set me off trying to prove my theory and ended up learning many things...including the fact that I was wrong !

Bob


Thanks for the info - this seems really counter-intuitive to me - it always feels like I'm getting a much shallower depth of field with longer lenses.

For example, I went to a wildlife park & took some photos of a donkey, very close up, with my 35L at about f1.6-f2.

The depth of field seemed similar to some distance shots of goats I took on the 300 F4 L at F4.

Maybe the answer is there isn't a huge difference in dof between F2 & F4, but this whole thing is screwing with my head & feels counter to what I've understood so far!

I think I need to read round this one a bit more!!!

Phil

[Wilt]

Thanks for the info - this seems really counter-intuitive to me - it always feels like I'm getting a much shallower depth of field with longer lenses.

For example, I went to a wildlife park & took some photos of a donkey, very close up, with my 35L at about f1.6-f2.

The depth of field seemed similar to some distance shots of goats I took on the 300 F4 L at F4.

Maybe the answer is there isn't a huge difference in dof between F2 & F4, but this whole thing is screwing with my head & feels counter to what I've understood so far!

I think I need to read round this one a bit more!!!

Phil

Phil, I posted earlier a key point: " With longer FL, the falloff from optimal focus is more rapid than the rate of falloff with shorter FL."

[Lester Wareham]

I understood that it did affect the dof, or at least the degree of background blur. This is demonstrated here:

http://www.the-digital-picture.com/Reviews/Canon-EF-180mm-f-3.5-L-USM-Macro-Lens-Review.aspx

See 'background blur comparison' halfway down page.

Phil

Yes it effects the background blur due to perspective. The DOF is the same for the same effective aperture, in fact a longer lens will have more DOF at a set aperture because it will have a smaller pupilary magnification, but that might be a bit technical.

Here is a little diagram I made a while ago to show the perspective effect on background, longer lens == smaller background area == makes the background look more blurred.

http://www.zen20934.zen.co.uk/photography/images/macro_perspective_drawing.jpg