questions about macro \"theory\"

[petiot]

Hi

i am thinking about buying a macro lens for a 10D. however i am not clear about what the term macro actually mean. It is often mentionned that macro lens achieve "1:1 life size reproduction" but the ration 1:1 is between what and what???

i thought it might be bwtween the real subject and the image produced by the lens, however i am not sure. do you hae any link that relate of this?

also i would like to know if anyone has an experience with the canon 50mm macro on a 10D is it good or is it worth spending twice the money on a 100 mm canon macro lens?

thank you for your answers

Dan

[PaulB]

1:1 means lifesize.
The image is the same size as the subject.
1:2 means that the image is 1/2 lifesize, 2:1 would mean that the image was twice (2x) lifesize.
I have no direct experience with the Canon 50mm Macro but I do know that it gives 1:2 on its' own and 1:1 with the optional lifesize convertor.
If you need 1:1 then the 100mm is the one to get as the price of the convertor has to be added and (I presume) it loses at least 1 stop of illumination anyway.
The 100mm also means that you are able to stand away from from the subject, not spooking timid insects etc., and lighting the subject with a shoe mounted flash (550EX) is possible - with the 50mm you are likely to be too close.
Hope this helps.

[rdenney]

I won't reiterate Paul's correct answer.

I just purchased the 50mm macro lens, and whether it is useful for the sorts of macro work you want to do I can't say. I bought it to have a general short telephoto (on the 10D) and also to do copy work. For those applications, the 1:1 converter isn't necessary. The smallest thing I need to copy is an old 2x3 inch photograph, and the 50 will focus down to an object 30mmx45mm (i.e. 1:2--twice the size of the 10D format). Also, the shorter working distance is useful--it keeps the camera lower down on the copy stand.

The 100 is a great general-purpose focal length for a full-frame camera, but it seemed too long on the 10D's smaller format for general-purpose use, to me. It might fit you just fine.

But if you want to do real macro work, like attempting those remarkable photographs of those butterflies posted here a day or two ago, then the 100 is the way to go. As Paul says, it will give you more working distance.

Rick "who works too slowly to photograph insects" Denney

[petiot]

Thank s for your answers. i didnt know the 50 mm was only 1:2 ratio. i think you provided me with the essential info to make a good choice

thank guys

Dan

[Webster]

PaulB wrote:
1:1 means lifesize.
The image is the same size as the subject.


I assume "the image" means the image on the film or sensor. How would the 1.6 conversion play into this? A picture shot at 1:1 that filled a 35mm frame would overfill a 10D frame.

[PaulB]

As it's an SLR ,in the 10D viewfinder "What you see is about 92% of what you get", this applies to any lens and magnification surely.

[rdenney]

webster wrote:

I assume "the image" means the image on the film or sensor. How would the 1.6 conversion play into this? A picture shot at 1:1 that filled a 35mm frame would overfill a 10D frame.

The image is the image, and it is a matter of convenience as to the size of whatever it is that is recording that image.

1:2 on the 50mm macro lens means that the minimum-focus image is half of real life, meaning that on a 10D, a 30x45mm piece of real life will get recorded on the 15x23 sensor. The same lens on a film-based Elan would yield a 48x72mm piece of real life on the 24x36mm film frame. The ant in the middle of the image, however, would be the same size in either case--half of its real-life size.

Stated another way, say you were taking a picture of a 15x23mm postage stamp. At 1:1, the stamp will fill the frame on a 10d, but it would not fill the frame on the Elan. But it would be 15x23mm on the film.

Thus, the 1.6 conversion affects only how much of real life you will see at a given magnification, not the degree of magnification. I recommend that when working with macro, just realize that your sensor is 15x23 and forget the conversion factor.

Rick "noting that Canon sells a 1:1 converter for use with this lens if you want 1:1" Denney