100mm 2.8L macro with 6D, shutter too slow in bright sunlight

[Cindy-Clicks]

When shooting with my 100mm macro in Av,  I cannot get a decent shutter speed even in bright sunlight with ISO at 1000.  I don't seem to have this problem with my 70D even though I am shooting at 200mm+.  The 6D is full-frame so it should actually be shooting faster. What is the problem?

[TTMartin]

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@ebiggs1 wrote:

EV is EV, no matter what size the sensor is.

An APS-C sensor will collect more light per unit area of the sensor, however the larger sensor on a FF sensor will collect the same amount of light in total.

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You've got that backwards, both sensors collect the same amount of light per unit area (i.e. square mm). The full frame sensor collects more total light because it has more units of area. (i.e. more square millimeters)

But as I posted before. Full frame and crop setting should be the same. The crop camera compensates for the difference in total light by applying more amplification at any given ISO. So as a photographer you will only see a difference in the quality of the output, not, in the settings.

[Cindy-Clicks]

These two images were both taken with the 6D ev metering,  f/13, ISO 800.  They were taken seconds apart.  The one on the left was 1/125 sec.  and the one on the right was 1/25 sec.  Why would there be such inconsistancy under the exact same conditions?

[TTMartin]

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@Cindy-Clicks wrote:

These two images were both taken with the 6D ev metering,  f/13, ISO 800.  They were taken seconds apart.  The one on the left was 1/125 sec.  and the one on the right was 1/25 sec.  Why would there be such inconsistancy under the exact same conditions?

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Where you using a flash?

[ebiggs1]

"You've got that backwards, both sensors collect the same amount of light per unit area (i.e. square mm)"

No, I really don't think I have it backwards. It is unrelated to sensor size. It is the density of pixels.  APS-C sensors usually have more densely packed sensors. You do have a point in that I am sure you can find a certain sensor vs sensor that does but not generally speaking.

I have heard people say full frame sensors receive more light than crop sensors. I have never found this to true.

Take the same lens along with exact settings on a FF and a APS-C, keep the distance from the lens and the sensor exact, then the FF will collect more light because the sensor is larger. It is recieving all the light the lens can project.

However, ensuring the other parameters are equalized, focal length, DOF, angle of acceptance, etc, you compensate for the different sensor sizes.

I grant you, this may be difficult to do since there may not be that exact match in lenses.

[TTMartin]

With a black background like that your best bet is to spot meter off of something else like a grey card or the grass and use full manual settings. Getting the settings for manual exposure is the only time I recommend using spot metering, as it will often cause the exact situation you have here when used with any of the automated modes.

[ebiggs1]

Cindy-Clicks can you post the photos with the exif left intact?  It is impossibile to tell from the sample you posted.  Except the one on the right is either OOF or has camera movement.

[Cindy-Clicks]

Of course it is going to have camera movement at 1/25.   I just checked the file info and it is exactly as I stated.  If I am shooting like this I should expect consistancy.  I just want to get to the bottom of this because there may be a problem with the lens/camera.

[TTMartin]

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@Cindy-Clicks wrote:

Of course it is going to have camera movement at 1/25.   I just checked the file info and it is exactly as I stated.  If I am shooting like this I should expect consistancy.  I just want to get to the bottom of this because there may be a problem with the lens/camera.

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No problem with the camera.

A black background will confuse almost any metering system.

Evaluative metering is weighted to the active AF point. Just very slight variations in where the camera is pointed can vary the exposure.

With a black background it is best to use full manual exposure settings.

Again, meter off of something other than the black backgound. One of these 12 x 12" Inch (30x30cm) White Balance 18 % Grey Gray Reference Reflector Card with a Carry Bag would be ideal. Or you can meter off of grass, or even the palm of your hand.

[ebiggs1]

"Of course it is going to have camera movement at 1/25.   I just checked the file info and it is exactly as I stated.  If I am shooting like this I should expect consistancy.  I just want to get to the bottom of this because there may be a problem with the lens/camera."

The sample photos do not show a more than 2 stop difference in exposure. 

"These two images were both taken with the 6D ev metering,  f/13, ISO 800."

f13 @ 1/125 with ISO 800

f13 @ 1/25  with ISO 800

 To me anyway they don't.

[Cindy-Clicks]

But it is actually 7 stops.  I took the original files to my local camera shop last night, and they could not provide me with an answer as to why this is happening.  I just want to know if it is problem with the lens or the camera.  This is very expensive equipment to be putting up with this kind of nonsense.