Duff 100mm Macro lens? Please help...

[happy_chappy]

Hey guys, just had my afternoon spoilt :(

 

I had a window of oppotunity to have a play about and set up a flower macro

shoot. Kit was the 5D and 100mm USM macro.

 

I couldn't get the richness of colours I was expecting and tried all ways to

meter, off green leaves, spot, partial, average, evaluative. I go to the point

where I had my gray card out and even my Gossen Lightmeter. I was getting TWO

stops difference between the camera and the lightmeter, even with a gray card.

 

So, some serious head scratching took place. Exposure compensation? - no.

ISO? no. Custom function? - no. What the....

 

I fetched my 10D out and did another meter reading (using a 28-105mm, filling

the viewfinder with the gray card) and this coincided with the Gossen.

"*$!%" I thought, the 5D is broken 8O

Then I put the 100mm macro on the 10D and the 28-105 on the 5D. Guess what?

The 10D was out and the 5D spot on :-k

So I have come to the conclusion that the lens is at fault. But how?

 

I rounded off by doing a test.

 

Gray card measured reflected light with the lightmeter gave me f5.6'4 @ 1/30s

then ... on the 5D -

 

50mm mk1 - f5.6 1/30

 

85mm USM - f5.6 1/30

 

100mm Macro - f5.6 1/8

 

24-105L - f5.6 1/30

 

(all shot within 40 seconds so no variance in lighting conditions).

 

What do you think could be the problem?

 

Can any of you guys with the 100mm macro see if it meters any different to

other lenses?

 

 

 

Not so HappyChappy

[PuppyDigs]

Bellows extension results in light loss the further out your go. A TTL metering system

measures actual light through the lens and thus there is no need to compensate. If you had

used your Gossen, you'd have to compensate manually to offset bellows extension.

 

Incidentally, a polarizer filter helps greatly in enriching plant shots by reducing reflections.

[happy_chappy]

Puppy Face

 

I wasn't using bellows... and you see, the difference between the 85mm and 100mm is 2 stops. TTL metering should have been the same for all lenses.

[ian_parkin]

The problem with macro is that as you approach 1:1 there is a lot of extension.... I know that you cant see it on the canon lens but its still there... if you used the lens normally it would meter correctly but as you focus close you lose 2 stops of light

Ian

[happy_chappy]

Ian,

 

Thanks for your explanation, it makes perfect sense now. As you say, because of the way the lens extends internally, you don't see it and consequently (well in my case) don't think of it having an effect.

 

I just tried a couple of exposures with the focussing racked out against my 24-105L and the exposures are reading spot-on. But by the time I get right down to the minimum focus point I had lost three stops of light.

 

I have learnt something new today and can thank you for it. Cheers!

 

Take care :-)

 

Happy Chappy (again!)

[PuppyDigs]

"I wasn't using bellows... and you see, the difference between the 85mm and 100mm is 2

stops. TTL metering should have been the same for all lenses."

 

I didn't say you were using bellows. I said you need to account for bellows extension. It's

merely the proper photographic term for the light loss you experience at high

magnification. Back in the day--a couple decades ago--bellows were mainly used for

lifesize and larger macro. Now they have lenses that extend enough for 1:1. However they

still suffer light loss due to the property know as bellows extension.

 

Sounds like you you could use a good reading of Shaw's "Closeups in Nature."

[happy_chappy]

Puppy Face,

 

Another day and something new learnt!

Thanks for clarifying what you said. I see what you meant now.

 

Thanks

 

H.C.

[lester_wareham]

There will be up to 2 stops of light loss at life size, measurement on my own EF 100mm indicate the internal focus method looses a bit less light than that.

[janice sullivan]

I use the 100 all the time and love it with my 5D. Lock your mirror and go for it. If your exposure is off fix it and don't worry so much about your meter. Macro (1:1) will never be on when it comes to the meter. Gotta love the digital, you can make your adjustment while you shoot. Tecs are good to know but the more you shoot the more you will appreciate the lens. Have fun...

[aleskoubik]

Happy, read the manual for the lens. You have to compensate depending on the magnification. 1:1 = 2 stops