Thursday, September 23, 2010
Wednesday, September 15, 2010
Ted C. MacRae is a research entomologist with an interest in beetle taxonomy and specializing in worldwide Buprestidae and Nearctic Cerambycidae and Cicindelidae. He is also the organizer of An Inordinate Fondness, the monthly blog carnival devoted to beetles. Read his in-depth interview at Nature Blog Network. Check out his excellent blog now:
Ted is one my most favorite bloggers and I have learned so much from reading his great blog. I have checked out the other blogs that Ted has featured, and subscribed to them too! I really enjoy learning up more on insects from reading their blogs!
Thursday, September 9, 2010
Full Flash is easy to explain. Take a look at my typical Full Flash Macro Photography setting: MT24EX on ETTL Mode, 40D on manual exposure mode: F11, 1/200, ISO100. At this setting and 1X magnification, you will most likely capture a dark/black frame if you don't turn the flash on. Do note that when you change the focus from infinity to 1X, you lose about 2 stops of light. Since all (or most of) the light is supplied by the flash/speedlight, that is why it is called Full Flash Photography. More about it here.
E-TTL (Evaluative-Through The Lens) is a Canon EOS flash exposure system that uses a brief pre-flash before the main flash in order to obtain a more correct exposure. E-TTL uses the same evaluative metering sensor used for ambient metering. The sensor is internal to the camera and takes its exposure via the lens so any filters added to the lens will also affect the E-TTL readings giving more accurate exposure information to the camera.
Since it's full flash photography where all the light is supplied by the flash/speedlight, it only makes sense that you control the exposure directly using the Flash Exposure Compensation (FEC) function rather than EV (Exposure Compensation), which is meant more for ambient exposure where no flash is used.
My MT-24EX is normally in ETTL mode at -1 FEC. You need to find out for yourself what your typical FEC is for your type of flash and diffuser. It won't be the same.
The key thing here is to adjust your FEC according to the scene. In fact, i pre-adjust my FEC even as i approach my macro subject, that is, if i don't get overly excited by my finding :D
Generally, there are only a couple of scenarios:
A scene with immediate background: normally the FEC will stay at -1, plus or minus 0.3 stops. This one was at -1.3 FEC
A scene with no background, i.e. nothing but just the subject itself to reflect the light from the flash/speedlight, I had to use -2 FEC, i.e even less light from the flash/speedlight compared to -1. -2 is the lowest I can go if i control via the camera body (40D).
If there is an immediate background but its dark, then the effect is the same. Look at this one, -2 FEC:
You can control the FEC from the speedlight itself and it will override the in-camera FEC. From the speedlight itself, you can go up/down to + or - 3 instead of just 2 in camera.
A scene with really bright background. This time the FEC was -0.33, i.e. more flash than -1 FEC. Don't be afraid to go to +ve : whatever it takes to expose/light up the scene correctly.
It is always good to get the exposure right or within the ball park so you will not need to adjust the exposure too much in post processing. Too much of exposure correction in post processing will result in excessive noise and should be avoided.
On my 40D, it is extremely easy to control the FEC. Just one press of this button on the top panel,
Press the button on top of the icon with +/- and flash symbols.
then rotate the big dial clockwise (to add) or counter clockwise (to reduce) the flash output
You will see something similar in the view finder as well.
It was quite easy to control FEC on previous camera Nikon D80 too. Just press and hold the FEC button with the left hand and turn the dial with your right. In fact, i think it was easier on the D80 but it's still not bad on the 40D.
On the lower end Canon model such as the 450D, you might have to go into the menu to dig up the FEC control. So unless you can register the FEC into "My Menu Setting", you might just want to control from the speedlight itself.
FEC (Flash Exposure Compensation) is not just for full flash macro photography though. I use it when I shoot event, portrait, etc - any time when flash is used.
So the next time you shoot full flash macro again, put these macro photography tips to good use. Analyze your scene better and dial in the appropriate FEC. Try your best to get the exposure right in-camera so you will have less work during post processing :)
Wednesday, September 1, 2010
But first, let's get a couple of definitions out of the way.
1:1 (or Life Size)
If your subject is 22mm long, and it fills up the width of your crop sensor's frame, then it's 1:1 or life size. For a Canon crop sensor DSLR, such as the Canon 40D, the sensor size is 22.2 x 14.8 mm. A great site to check for specifications like this is Dpreview.com. That is where i got my sensor size: http://www.dpreview.com/reviews/canoneos40d/page2.asp
You can even find it by just googling "40D sensor size" :D.
Magnification = sensor width / # of mm captured
= 1X (approx)
= 2X (approx)
Magnification = sensor width / # of mm captured
= 3X (approx)
Yes, it's that simple :)
Another illustration just to show you the different magnifications when you shoot a real life subject at different magnification and also with a FF (Full Frame) camera. Let us assume the soldier fly image was shot with a 40D (crop sensor) at 1:1. The yellow, red and blue frames are what they would look at at 2X, 3X (crop sensor) and 1X (FF) respectively.
Based on the input from a few forum members, you can get up to 2:1 by adding a full set of 68mm of Kenko Extension Tubes to a 90mm, 100mm, and 150mm macro lens.
Theoretically, the calculation goes like this:
Magnification gained = # of mm of tubes used / focal length
so if you used all 68mm of tubes on say a 100mm, you should gain an additional 68/100 = 0.68X
Add the native 1X from the macro lens and you get 1.68X. However, the actual measurement tells us you can get up to 2:1 magnification.
It is even more surprising to hear that you can get up to 2:1 too on the 150mm.
Okay, I know you magnification junkies out there won't be happy with 2:1, you want more. You can still add a 1.4X Teleconverter to your setup and get up to about 2.5X. Actual macro magnification may vary so again, go shoot an mm ruler:D
So the best way to calculate/measure macro magnification is to shoot an mm ruler. Period :)
Oh i assume you already know how to achieve higher magnification. There are many ways, but I personally prefer the use of extension tubes, as discussed here, and a 1.4x teleconverter too, if you want to get even higher magnification. Diopter lens like the Raynox DCR250 is okay too but i prefer extension tubes better.