exposure help! sunny16 inaccurate!

J

Jonathan12uiz

Well-known member
OK... this is going to get confusing so buckle up!

The GH1 has a 2x crop sensor, meaning based of a full frame sensor, the field of view would equal 2x the focal length of a full frame sensor. Correct?

So 25mm on the GH1 is = a 50mm full frame, 50mm = 100mm, etc. Correct?

So lets say I take a picture with the GH1

Settings are 50mm focal length, 1/160 shutter speed, 160 ISO, on a sunny day.

According to the SUNNY16 rule my picture should come out perfect.

NOPE!

My picture is horribly underexposed. See pic below:
View attachment 25731

BUT!

If I divide my f-stop by 2, just like how I had to multiply 50mm x2 to know that it's a 100mm full frame picture, I get an f8.0.

My picture is now perfectly exposed. See pic below:
View attachment 25730

THIS IS WHERE IT'S CONFUSING!

Our crop sensors' 2x multiplier should only affect focal length in terms of Field of view. Meaning light absortion/exposure should remain the same @ any f-stop.

So... Why the hell am I having this issue?
 
This is my only explanation. Correct me if I'm wrong.

Lets use a 5DmkII for example:

Lets say it's sunny. So sunny16 says f16 with shutterspeed the recipical of ISO.

ISO set to 160, shutter speed set to 1/160, f-stop set to 16.

Theoretically, A full frame camera should give me a great picture.

Why is this? lets look at some numbers.

FULL FRAME now...

@ 50mm an f16 aperture equals a 3.125mm opening to let in light. SO...

the Full Frame sensor gets X amount of light, BUT!

Since I have a 2x smaller sensor doesn't that mean that 2x amount of light is not recorded onto the sensor?

So to get the same amount of light to get to the sensor I would need 2x the opening of 3.125 which is 6.25mm.

Which @ 50mm = f8, because 50/8=6.25.

Am I wrong?
 
The amount of light will be exactly the same. The exposure depends on things such as how accurate the ISO is; there are many reports that say that the GH1's true sensitivity is different from the 7D's, when both are at the same ISO.

I don't have the answer you're looking for, but I can absolutely assure you that the "crop factor" doesn't change the iris in any way.
 
Barry_Green said:
The amount of light will be exactly the same. The exposure depends on things such as how accurate the ISO is; there are many reports that say that the GH1's true sensitivity is different from the 7D's, when both are at the same ISO.

I don't have the answer you're looking for, but I can absolutely assure you that the "crop factor" doesn't change the iris in any way.
Click to expand...

man... this is what is currently boggling my mind. I want to know why I have to 1/2 my f-stop to get correct exposure using sunny16.
 
Jonathan12uiz said:
I am aware of that, because the opening will always be 6.25mm @ f8 of 50mm, but why is the amount of light recorded not = on a 2x crop sensor vs a full frame?
Click to expand...

You may have answered your own question. maybe the crop sensor lets in less light, hence the reason the 5d does so well at night. because it's a full frame. Or it could just be the sensativity of the sensor. I would just set my exposure to the enviornment and say the hell with sunny 16.
 
maranfilms said:
You may have answered your own question. maybe the crop sensor lets in less light, hence the reason the 5d does so well at night. because it's a full frame. Or it could just be the sensativity of the sensor. I would just set my exposure to the enviornment and say the hell with sunny 16.
Click to expand...

I just didn't realize how different digital is from film. I knew there were some differences, but I didn't realize it many handicaps if trying to learn the OLD basics. I'm trying to improve my photography and I want to stop relying on digital on camera exposure meters and light meters, I want to be skilled enough to do without it.
 
Jonathan12uiz said:
I want to stop relying on digital on camera exposure meters and light meters
Click to expand...

Why? These basic tools of photography are just as valid now as they always have been. But it should well be noted that the sensor in your current camera is about 1/10 the size of a piece of 35mm film. It's likely going to be less sensitive. And as you've found, the ISO is relative. ISO 100 on the 5D is not ISO 100 on the 7D/550D. Only took a few moments on a dark set to confirm THAT little truism. When my cinema light meter didn't match up to anything on the 5D! Similarly, the GH1's ISOs don't line up to either film or any of the other cameras I'd bet.

So do what all good photographers and cinematographers do. Learn you camera. Or do you plan to walk onto a film set and invoke the Sunny 16 rule? Dust off that Luna-Pro and make up a set of exposure tables to match your camera. Problem solved.
 
PerroneFord said:
Why? These basic tools of photography are just as valid now as they always have been. But it should well be noted that the sensor in your current camera is about 1/10 the size of a piece of 35mm film. It's likely going to be less sensitive. And as you've found, the ISO is relative. ISO 100 on the 5D is not ISO 100 on the 7D/550D. Only took a few moments on a dark set to confirm THAT little truism. When my cinema light meter didn't match up to anything on the 5D! Similarly, the GH1's ISOs don't line up to either film or any of the other cameras I'd bet.

So do what all good photographers and cinematographers do. Learn you camera. Or do you plan to walk onto a film set and invoke the Sunny 16 rule? Dust off that Luna-Pro and make up a set of exposure tables to match your camera. Problem solved.
Click to expand...

Good point, although I dabble in Photography just as much as video right now. I actually work for LIFETOUCH now and I didn't realize how much I depended on digital readouts on camera to take a picture. Our boss challenged the staff to take pics of people without the use of a light meter or on camera exposure meter and we all looked like NOOBS. Made me want to learn more, ya know.

I do get what your saying though, as long as I know my cam, I'll be fine.

This is more from a photography standpoint though, I've got my manual settings for exposure during VIDEO pretty much down.
 
Don't forget that these sensors have a narrower dynamic range than film as well. I have found that I need to be a lot more precise in establishing exposure. I think we often have a half stop of flexibility to get it right. With film (in still photography) there was always more or less 2 stops of head room. It's a bit more like shooting slides. If you overexpose, there won't be anyway to recover the detail in the highlights, and if you underexpose, all you have is grain (in this case noise).
 
yoclay said:
Don't forget that these sensors have a narrower dynamic range than film as well. I have found that I need to be a lot more precise in establishing exposure. I think we often have a half stop of flexibility to get it right. With film (in still photography) there was always more or less 2 stops of head room. It's a bit more like shooting slides. If you overexpose, there won't be anyway to recover the detail in the highlights, and if you underexpose, all you have is grain (in this case noise).
Click to expand...

I take it you're not familiar with E6?
 
Jonathan12uiz said:
Good point, although I dabble in Photography just as much as video right now. I actually work for LIFETOUCH now and I didn't realize how much I depended on digital readouts on camera to take a picture. Our boss challenged the staff to take pics of people without the use of a light meter or on camera exposure meter and we all looked like NOOBS. Made me want to learn more, ya know.

I do get what your saying though, as long as I know my cam, I'll be fine.

This is more from a photography standpoint though, I've got my manual settings for exposure during VIDEO pretty much down.
Click to expand...

And the difference is what? If you know your exposures for video without a meter, set the camera the same way for a still, then work the translations to get your shutter where you want it. A stop is a stop is a stop.. video or stills.

And shooting without a meter shouldn't be any big deal. None of my vintage glass meters AT ALL on my Nikon film camera. No meter, no preview or review. Shoot and head to the film shop and get your film developed. Just the way it should be!

It also helps to know your camera and your business. If you shoot portraits all day, and you typically shoot a 1/125 like I used to onto VPS (ISO 160, but everyone printed it at 125 or so), then you develop an eye for knowing what aperture you should be on based on light levels.

When I shoot my DSLR for stills or video, I treat my ISO like I have a film stock. And I know I typically want to be at F4 or F5.6. This means I can eyeball the light levels all day and know when I am close. And I can tell the gaffer what instruments he'll likely need to bring in to get my light levels right. If you're up and down all day on your ISO or aperture, your light levels will vary all the time, and the lighting crew will be ready to string you up by your neck.

Keep things simply in photography or video. Contrain things like you had film in the camera, and you'll make things a lot easier on everyone.

(And use a meter)
 
Jonathan12uiz said:
What is e6?
Click to expand...

aka Chrome
aka Slide Film

aka "You've got about half a stop (maybe 2/3) up or down or you lose the blacks or the whites. Shooting these DSLRs is just like shooting chromes. Many of us old timers grew up on Kodachromes, or Fujichromes. So it's no big deal to us.
 
PerroneFord said:
I take it you're not familiar with E6?
Click to expand...

I shot E6 for 15 years.


Far less latitude than negative film. (For 35mm at least, a little more room with medium format)
There were always big consequences with pushing and pulling.
You got to get it right in camera.

I think we are saying the same thing.
(Perrone - Didn't know if your question was pointed at me)
 
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Jonathan12uiz said:
FULL FRAME now...

@ 50mm an f16 aperture equals a 3.125mm opening to let in light. SO...

the Full Frame sensor gets X amount of light, BUT!

Since I have a 2x smaller sensor doesn't that mean that 2x amount of light is not recorded onto the sensor?

So to get the same amount of light to get to the sensor I would need 2x the opening of 3.125 which is 6.25mm.

Which @ 50mm = f8, because 50/8=6.25.

Am I wrong?
Click to expand...

I admire your use of math, but the application is wrong.

Most lenses projects a circular image which are supposed to be a particular radius when it hit's the film or imaging chip that it's designed to be used with. When Panasonic or any other manufacturer tells you the crop factor is 2X, what they mean is that the surface area of the imaging chip is only using about half the radius of the image circle of a typical 35mm still lens. The amount of light that reaches any photo receptor on that chip at a given aperture is the same as it would be on the same size area of a piece of 35mm film under the same part of the image circle.
 
PerroneFord said:
aka Chrome
aka Slide Film

aka "You've got about half a stop (maybe 2/3) up or down or you lose the blacks or the whites. Shooting these DSLRs is just like shooting chromes. Many of us old timers grew up on Kodachromes, or Fujichromes. So it's no big deal to us.
Click to expand...
Especially in the highlights. Video has more range in underexposure, but very little in overexposure. It's a lot more like reversal film in that aspect.
 
thanks guys. I've done another test. It was overcast today and I shot @ f5.6 14-100mm and all the shots exposed the same. The funny thing though is that they looked exposed correctly. That was using sunny16s rule, I just don't know why the sunny day @ f16 is underexposed. WEIRD. No matter what though I have meters to get it right, I just wanted to know why the camera wasn't exposing they way i THEORIZED it to. Ya know.
 
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