Questions on macro lense specs

Qarik · November 6, 2007

okay what does it mean that a 1:1 reproduction ratio?

there is trade off in the max focal length vs the minimum focusing distance correct? the closer you can focus the "less" focal length you need for same "magnification"? Am I thinking about that correctly?

so for example the 200mm micro-nikkor min focusing = 0.5m, the 60mm micro-nikkor min focusing = 0.22m. The actual magnification these can achieve ae not that far apart because although the 200mm is 3x the 60mm, the min focusing distance are almost 3x apart as well.

Though one of the advantages of the 200mm lense in this case is that you can be farther away from your subject so as not to scare an insect for example.

Any other trade offs I should be aware of?

Lord Vetinari · November 6, 2007

1:1 means that 1 cm of subject will appear as 1cm of image on the sensor.

Yes you are correct about the focal length of macro lenses- The longer the focal length, the further away from the subject you are at minimum focus (ie 1:1 mag).

The trade off on longer lenses is they are much more expensive, difficult to handhold (150mm or >) and require higher shutter speeds. The advantages are the longer subject distance and often better bokeh (background blur).

I normally recommend a macro lens around 100mm as the best all round lens.

Brian V.

JetCrocodile · November 6, 2007

Lord Vetinari wrote:

Yes you are correct about the focal length of macro lenses- The longer the focal length, the further away from the subject you are at minimum focus (ie 1:1 mag).

I normally recommend a macro lens around 100mm as the best all round lens.

Brian V.

Could you please spot some light on how extension tubes will affect magnification and distances from the subject in case of Macro lenses?
For example if one will add some extension tubes to Sigma 105mm?

Lord Vetinari · November 6, 2007

JetCrocodile wrote:

Could you please spot some light on how extension tubes will affect magnification and distances from the subject in case of Macro lenses?
For example if one will add some extension tubes to Sigma 105mm?

With a sigma 105mm lens around 34 mm of ext tubes will give 1.5:1 mag with a focus distance of about 3" in front of the lens and 68mm of tubes will give 2:1 with about 2" focus distance in front of the lens.

The classic formula for this with a 1:1 macro lens is mag= 1+ length of tubes mm/focal lengthmm
Trouble with this formula is it does not take account for the shortening of focal length in macro lenses at minimum focus.

brian V.

JetCrocodile · November 6, 2007

Lord Vetinari wrote:

With a sigma 105mm lens around 34 mm of ext tubes will give 1.5:1 mag with a focus distance of about 3" in front of the lens and 68mm of tubes will give 2:1 with about 2" focus distance in front of the lens.

The classic formula for this with a 1:1 macro lens is mag= 1+ length of tubes mm/focal lengthmm
Trouble with this formula is it does not take account for the shortening of focal length in macro lenses at minimum focus.

brian V.

Many thanks! The subject is more clear to me now.
Are there any lense which provide magnification higher than 1:1 without extension rings?

JetCrocodile

Lord Vetinari · November 6, 2007

JetCrocodile wrote:

Many thanks! The subject is more clear to me now.
Are there any lense which provide magnification higher than 1:1 without extension rings?

JetCrocodile

Sort of - the MPE-65 macro lens starts at 1:1 and zooms to 5:1 magnification however it's longest focus distance is 4" in front of the lens and it effectively has the extension tubes built in- the length of the lens more than doubles going from 1:1 to 5:1.
You really need to get used to shooting at 1:1 before thinking about this lens.

brian V.

Qarik · November 6, 2007

Lord Vetinari wrote:

With a sigma 105mm lens around 34 mm of ext tubes will give 1.5:1 mag with a focus distance of about 3" in front of the lens and 68mm of tubes will give 2:1 with about 2" focus distance in front of the lens.

The classic formula for this with a 1:1 macro lens is mag= 1+ length of tubes mm/focal lengthmm
Trouble with this formula is it does not take account for the shortening of focal length in macro lenses at minimum focus.

brian V.

hmmm....that formula doesn't make sense to me in one regards. If I put 50mm tube on a fixed 50mm lense that is mag of 2, Okay that is fine. If the same tube on say 50-100mm lense, then the :mag" is better on the 50mm focus (2) then the 100mm side (1.5)?

JetCrocodile · November 6, 2007

Lord Vetinari wrote:

Sort of - the MPE-65 macro lens starts at 1:1 and zooms to 5:1 magnification however it's longest focus distance is 4" in front of the lens and it effectively has the extension tubes built in- the length of the lens more than doubles going from 1:1 to 5:1.
You really need to get used to shooting at 1:1 before thinking about this lens.

brian V.

Looks like Canonians enjoy more macro choices compared to Nikonians :cry

Lord Vetinari · November 6, 2007

Qarik wrote:

hmmm....that formula doesn't make sense to me in one regards. If I put 50mm tube on a fixed 50mm lense that is mag of 2, Okay that is fine. If the same tube on say 50-100mm lense, then the :mag" is better on the 50mm focus (2) then the 100mm side (1.5)?

Qarik the first statement is only true if it's a 50mm macro lens capable of 1:1 magnification without ext tubes. For a normal non macro lens the formula = length of tubes/focal length.
This actually works quite well so a 50mm lens with 50mm of tubes will give 1:1 magnification.

Brian V.

Qarik · November 6, 2007

follow up question
Complete noob question. I noticed the macro lenses are designated by 60mm or 105mm...not 18-105mm for example. Does that mean these lenses can not "zoom" in or out? Is this a "fixed focal length"?

Followup question: okay so 1:1 means the size of the image on the sensor is the same as the size of the actual object. So 1:1 is only makes sense for "fixed focal lengths" lenses right?

Lord Vetinari · November 6, 2007

Qarik wrote:

Complete noob question. I noticed the macro lenses are designated by 60mm or 105mm...not 18-105mm for example. Does that mean these lenses can not "zoom" in or out? Is this a "fixed focal length"?

Followup question: okay so 1:1 means the size of the image on the sensor is the same as the size of the actual object. So 1:1 is only makes sense for "fixed focal lengths" lenses right?

Not certain what you are asking. 1:1 is just the magnification of the lens system- it does not have to be a prime lens. For example if you reverse the typical kit lens supplied with dslrs directly onto the body of the camera, the zoom lens is then quite capable of going from 1:1 to 3:1 magnification depending on the zoom level.
Brian v.

Questions on macro lense specs

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