How to use a100mm Macro +Canon TCs

[david_khoo]

Hi to one and all again

I've just tried using a 100mm Macro + 1.4x and a 2xTc couple of days

ago. when using this setup, i did not use the ML3, instead use the

540ez off-shoe flash setting. The flash was to left using a mini-

tripod, plus a portable reflector to bounce the flash. I manually

set the camera to a shutter speed of 60 at f16 and flash compensation

of 1 or 2 stops due to the tc involved.

 

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When the results come back from the lab, with the 1.4xTc was quite

all right just needs some fine tuning the next time, but with the 2x

what i got was just a BIG BLACK BACKGROUND. Please advise what went

wrong, I was quite sure i couldn't be off-course by that much!!

 

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Warmest Regards

David

PS: the lens cap was off!! - Ha! ha! ha!

[david_khoo]

Sorry just a quick note

The day was a overcasted day in fact rain clouds have just gather

over the horizon. The flash compensation was set to +1 for the 1.4x

and +2 for the 2x

 

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The big black background is a little extreme. you could see alittle

of the image but generally still black. film used is asa100 slide.

Was shooting bugs that day

 

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thanks David

[bobatkins]

It's TTL flash. Why are you adding compensation for the TCs?

[david_khoo]

Hi Bob

 

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I made the assumption that i have to compensate for the Tc due to the

f/stop reading of 2.8 instead of 5.6 which normally with any L-lens

the f/stops jumps its value according to the Tc. Wrong assumption

huh?

regards

David

[don_baccus]

The TTL flash meters the actual light coming in through the lens when

it's stopped down, it doesn't really care what the f-stop is - it can

SEE the light, so to speak. It keeps the flash on until X amount of

light has come in through the lens, then turns it off.

 

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The fact that the display shows the wrong aperture is irrelevant,

though a pain if you're using an EXTERNAL flash meter (it doesn't

adjust the display for the extension factor as you focus close,

either)

[glen_johnson]

I guess I'm surprised that the results with the 1.4 were OK, but with the 2 weren't.

 

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I would guess either of two answers.

 

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1. Your 2x TC and camera combo weren't working right. Is this the Canon EOS 2x? If yes, then you also had an extension tube in there. Maybe the contacts were dirty on something.

 

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2. Are you sure the 1.4x results were good? Were the negatives thin? Were you close to the toe of the characteristic curve for the film? f/16 is pretty small. Its common for macro work, but it is still small. The ML3 has a very low guide number. It can't put out much light. Compared to the 540EZ, the ML3's output power is sort of like a match compared to a bon fire. If the negatives were thin with the 1.4x, my guess is that you just snuffed them out entirely with the 2x. Try again, with a tripod. Use Av instead of 1/60th and f/16. Set f/8 or f/5.6. Be prepared for a long shutter speed because ambient light may make up a significant fraction of your exposure.

[vince_farnsworth1]

One thing you have to be very careful about in macro with TTL flash is

that the focusing point that you use ends up where you are metering

the flash light. In other words, if you have a camera with five focus

points (like an A2 or 1N), make certain that the focus point in use is

where you want to meter the light. If the composition is such that

the focus point falls on the background somewhere, you will get a very

dark exposure since there was little or no light being reflected back

to the sensor. If you shoot bugs on flowers, choose a focus point

that falls on the bug or the flower in the final composition. Also,

if the flower or bug is very light-colored (e.g., white or bright

yellow), you must use flash exposure compensation because the light

reflected back to the sensor will be more than from 18% gray and turn

off the flash early. I appologize if all this is obvious to you but

it is something that I have found through experience to be very

important.

[vince_farnsworth1]

I just reread my response and noticed a very obvious error. If the focus point falls on the background and there is little or no light being reflected to the sensor, the flash will be putting out maximum power to compensate and will likely overexpose, not underexpose, the picture. Sorry about that. Anyway, the rest of what I said is correct. It is still very important to have the sensor where it can accurately meter the reflected light. By the way, I use manual focus for macro so the focus point selected is just for the flash sensing and not for actual focusing.

[bugbob]

Using David's setup in AV mode, I've had the same results mentioned by Vince - overexposure. I talked with Jack Kelly Clark (author of Canon's Macro Book) about the technique (Canon EOS A2, Canon TC, 100mm macro lens, off camera flash) and he said to shoot in manual mode initially at 1/film speed at �/11 then use reciprocity to adjust dof as needed. All is well again!