| Macro Magnification |
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| Written by Cyrus Khamak | |
| Thursday, 21 June 2007 | |
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Thank you all for your interest in knowing my thoughts on Macro photography and my gears used to shoot Mega Bee and Mega Fly.
In an overview of Macro photography a 1:1 Macro is defined as following: In a typical crop sensor DSLR such as Canon 10D and 20D, Nikon D70, D50 and D2x, Fuji S2 and S3, the sensor size is around 15 MM by 24 MM or around 3/4 on inch by 1 inch. Now, if you have a subject which is 24 MM in length, for a 1:1 Macro, it should fill the frame from edge to edge, with NO room for further crops. A 2:1 Macro is defined as following: If you have a subject that is only 12 MM (1/2 inch) in total length, it should occupy the whole frame with no further room for further cropping. And finally, for a 4:1 Macro, a subject 6 MM (1/4 inch) in total length, should occupy the whole frame Now, there are those who think capturing a 4:1 or a 5:1 macro is a matter of having the lens but this sentence is so far away from the reality as many other factors come to play. One literally becomes limited by the laws of physics, the available technology and one's skills as a Macro photographer. At a 1:1 macro level, under a bright sun at F32 at a distance of one foot (31 CM), your DOF with a 180 MM Macro lens is less than 1/16 of an inch or about 1 MM. (Here, Depth of Field Calculator) Your shutter speed at ISO 100 is 1/25 second or at ISO 400, 1/100 second which is barely enough for a moving subject. The slightest movement by the subject and it's out of focus. And don't forget, as you move up to higher F stops to achieve more DOF, usually beyond F16, you become defraction limited which means that you start losing detail, HERE, some good reading. . Now, at a 4:1 Macro level, the equation is quite different. For one thing, with a set up like the one that I used in my Mega Bee and Mega Fly (Tamron 180MM macro, about 150MM extension tube and one 2X converter), the effectiveness of your prescious light is reduced by 10 times and your DOF field much smaller. The tiniest movement by the subject or shake in the camera and you are out of luck and you have to locate your subject in your now much DARKER viewfinder.. This is all true for a live and moving subject. For a stationary subject, it's an easier task and that's why you see a lot of close macros made of dead or frozen subjects. What I have mentioned so far is only a part of the whole story and that is why Macro photography is the most challenging. Even when you do get a high magnification, then you must expect to have good detail when viewed at 100%. Now, by the above definition of a 4:1 macro, the following photo could be considered a 4:1 Macro:  But, this is not a 4:1 Macro. It's actually an over sharpened crop of this:  Which is a crop of the following shot which is barely a 1:1 Macro.  . So, you see, sometimes it's hard to distinguish a crop from a full frame shot. Also, detail is not how sharp the hair sticks out but also detail in other areas, tonal range and transitions. Contrast is good but remember, it should not kill detail. Contrast essentially tries to fit all tonal ranges in an image, in a smaller box! Contrast also creates the illusion of sharpness and that's maybe that's why we push the contrast sometimes more than we should. I hope that helps. Kind regards, Cyrus Khamak macro 
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Comments (3)
  written by Robert Seber, June 29, 2007
Is the Don Fleming DOF calculator accurate for macro? According to Wikipedia http://en.wikipedia.org/wiki/Depth_of_field the calculations change a lot for macro.
written by cyrus, June 30, 2007
Robert,
Thanks a lot for the excellent read, I read some of it but will go back to it again when time permits. As you may remember, we have always maintained not to get fixated by the numbers we derive from general formulas and also, we have discussed issues such as equations being different as you go higher on magnification and issues such as effective DOF. ALSO, I have in many, many occasions reminded my friends to tilt and swing their camera which will have a great effect on the background bokeh and bokeh colors and the apparent DOF. I was particularly happy to read his small hint at sharpening increasing DOF which as you, it's an issue we have discussed from day one and recently with the small exercise we have had which I hope to be able to follow up and finish soon. Also, we have discussed diffraction and it's relevancy to the subject matter and the frog photo in "it's all in the conversion" at F38, way beyond the diffrection limit.http://megashot.net/content/view/15/46/ I hope I have the time soon to have another discussion about these matters. written by Robert Seber, July 25, 2007
Selective sharpening has become a very important tool to me now!
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