Lens Magnification Question

[SirvoN]

I'm looking at the following specs of two Canon lenses and can't easily
determine which lens will give me the largest magnification for macro type
work (I realize a macro lens would be better). So - if I'm shooting a
mantis which would yield the largest mantis head in print using a EOS 10D?
They both are around 1:5 ratio but does minimum focus distance factor in?

Canon Zoom Telephoto EF 100-300mm f/4.5-5.6 USM Autofocus Lens
Filter Size 58mm
f/Stop Range 4.5-32 / 5.6-38
Minimum Focus Distance 4.9'
Magnification 1:5
Zoom/Focus Control 2 Touch
Angle of View 24 to 8 Degrees
Groups/Elements 10/13
Length 4.8"
Maximum Diameter 2.9"
Weight 1.18 lb

Canon Zoom Wide Angle-Telephoto EF 28-135mm f/3.5-5.6 IS Image Stabilizer
USM Autofocus Lens
Filter Size 72mm
f/Stop Range 3.5-22 (5.6-36)
Minimum Focus Distance 1.64'
Magnification 1:5.26
Zoom/Focus Control Two-touch (twist)
Angle of View 76 to 18 Degrees
Groups/Elements 12/16
Length 3.8"
Maximum Diameter 3.1"
Weight 1.1 lb

Thanks!

[[blur]]

I'm no mathematician but I'd say the long telephoto will give you the greatest mag. Throw some tubes on it and the close up will rock with posterised BG.

[steven]

Answer first: 100-300mm lens will have the larger image at it's minimum focus.

The magnification is the key number here. The 1:5 of the 100-300mm lens states that 1 unit on the sensor will show 5 units in real life. So say the mantis head is 5mm (I have no idea about bug sizes) it will be 1mm on the sensor. Now depending on the size of the sensor will tell you how much of the view will be filled.
1:5.23 < 1:5 < 1:2 (50mm "macro") < 1:1 (true macro) < 5:1 (MP-E65)

[SirvoN]

Thanks for the responses guys. Funny thing is I had a opportunity to evalutate both lenses - so I jumped at the opportunity to compare magnification and would you believe the 28-135 actually produced a significantly larger subject shooting both lenses at their minimum focus distance? Very confusing for me since I thought (based on the specs) the 100-300mm would produce the larger subject on the sensor plane.

Thanks again.

[cmM]

if you want a big mantis head, I'd think about a macro lens.... 180mm macro... that'll give you a pretty big head. The biggest advantage of macro lenses is the ability to get closer to your subject without having to use tubes etc...

[ron chappel]

........i jumped at the opportunity to compare magnification and would you believe the 28-135 actually produced a significantly larger subject shooting both lenses at their minimum focus distance? Very confusing for me since I thought (based on the specs) the 100-300mm would produce the larger subject on the sensor plane......

I checked the specs of the 100-300 on several sites.There is some variation in the figures but they all show the same thing-the 100-300 usm will definitely give more magnification than the 28-135 IS.
Did you have both lenses zoomed to their longest setting?

[steven]

I agree with ron, according to Canon's own lens chart 100-300 @ 300mm is a mag of 0.20 and 28-135 @ 135 is 0.19

But that little of a difference might be hard to objectivly tell.
Are comparing the images after taking them? and not just relying on looking through view finder?

[Tom W]

the one great advantage of the 100-300 here is that you can obtain the same macro magnification (OK, a tiny bit better) while shooting from more than twice the distance from the subject that the 28-135 would allow.

[Jim_T]

I've got the EF 100-300 lens.. I use it as a poor man's macro with a 58mm 500D close up lens screwed on the front. It works pretty well..

Extended to 300mm, it can focus on an object about 19 inches away (480mm). The DOF is pretty shallow.

I guess an extension tube would work too.. Probably a bit cheaper..

[steven]

Jim,

true but you will loose less light with the 500D so you can use a smaller apature for better DOF.

[ron chappel]

For what it's worth........
The sigma 70-300 apo macro super II is also a good sharp lens.
It's about equal best (with the canon 100-300 usm) of the consumer zooms.The advantage of the sigma is genuine close focus ability (1:2 i think) ,allthough it loses the excellent fast focus performance the canon has

[tim]

That sigma lens is a good lens, gives nice pics, but I wouldn't use it for macro myself. Marco lenses are quite specialised and do a great job. It's a bit slow at F4 or so, but for macro work that's fine.

[SirvoN]

I checked the specs of the 100-300 on several sites.There is some variation in the figures but they all show the same thing-the 100-300 usm will definitely give more magnification than the 28-135 IS.
Did you have both lenses zoomed to their longest setting?

Yep - had both zoomed in as far as possible and set the focus at minum (manual) and moved the camera to achive focus. The 28-135 produced a larger subject which doesn't make sense based on the magnification specs.

[pierrot]

Same ratio => same magnification. The only difference is that with a tele you can be farther from the mantis (brrr)...
Btw. why will you snap such a horrible insect? :?