Exposure questions...with pictures!

wildviper

Hello,

It must be late cause I can't make sense of the experiment that I just ran. Hopefully, someone here can tell me what is going on as I am lost. (And yes I am reading The Negative as well as Understanding Exposure).

For a couple of years I wanted to do this cause I want more control over my expsoures than having to always adjust in LR or Photoshop.

So, I did the test tonight. It may not be very scientific for the more "demanding" of us, however, I did it to start getting a basic understanding of things.

I setup two foam boards - one white and one black(not deep black) on a chair, lit with our room light. I measured the light falling on the boards with a Sekonic lightmeter (L358). The various spots I measured, the reading was coming the same(except a couple of places). This led me to believe that the boards were more or less evenly lit.

I did try and hold the meter in pretty much the same pointing angle...to camera. I kept checking in the middle to make sure the reading remained the same..it did.

• Camera was mounted on a steady tripod and never moved.
• No flash used. Constant light source
• All Aperture priority
• Spot & Matrix readings read the same unless indicated
• The light meter read 1/40th, f4, ISO 1600.
  • There were a couple of smaller spots were it read 1/30th, but I think it was small cause a reading right next to it would revert to 1/40th
• Shot in RAW and JPEG. Worked on JPEG cause it was faster.
• White Balance in LR. In Camera it was set to to Incandescent
• No Active D-Lighting
• Camera: Nikon D300s / Lens: Nikon 50/1.8
• ISO: 1600 - Aperture F/4

Anyways, here are the pictures I got and the setting for the camera.

Picture of All White board

W1. Middle Exposure EV 0 : 1/100



W2. EV +1 : 1/50th



W3. EV +2 : 1/25 - I prefer this one since the board looks similar to this



W4. EV +1 1/3 : 1/40 - This is what the meter suggests




Picture of All Black board in exactly the same position as the White above

B1. Middle Value EV 0 : 1/10



B2. EV -1 : 1/20



B3. EV -2 : 1/40th - What the lightmeter says - This is what I prefer here




Picture of both boards (half/half) in pretty much the same position as above - Now MATRIX METERING ONLY for these shots below

WB1. Middle Value EV 0 : 1/30



WB2. EV +1 : 1/15



WB3. EV -1 : 1/60



WB4. EV -1/3 : 1/40 - This is what meter suggests and what I like




Ok...so what is this telling me??? That is where I am lost now. Especially cause when it is the white board only, I prefer the W3 better which is 2/3rds of a stop more than what the meter is suggesting. In the other two cases, I agree with the meter and prefer those readings. B3 and WB4.

Someone please make sense of this...I have had enough for today!

Thanks

Richard

The thing that took me the longest to fully grasp about exposure is that the camera will expose so that 0 EC is middle gray. So when you meter for something that's white, it will turn gray unless you use positive exposure compensation, while something truly black needs negative compensation to look black. Zero doesn't mean right, it means gray. The examples you posted are what pretty much what one would expect to see.

colourbox

Totally agree with Richard, The meter does not know you are looking at white or black. It thinks you are trying to take a normal picture, therefore, the meter is going to want to drive white and black to a typical middle gray.

Maybe a better test would be to see what happens if you shoot a gray scale with several shades from white to black. It would be closer to the range of tones in a normal scene that the meter is programmed to expect. If you show a matrix meter just white or black, either is so extreme the meter cannot resolve that to any known "typical" scene so it gives up and shifts it toward average gray. That's when you compensate (with exposure compensation) or, you decide not to let the camera guess any more, and so you simply go into manual and tell it exactly what you meant.

wildviper

Right, I understand that. My confusion is stemming from which way should I adjust the EV. For example, in W3, I like that one..but it is clearly not what the Sekonic lightmeter suggested. That is EV +2 which by the Zone system, makes sense. But based on the incident lightmeter it is wrong. Sure, I can adjust in post, but that is not the point. I want to try and get the exposure nailed down as much as I can. Thus this exercise.

Now, if you look at the other two scenarios, the lightmeter and what I like match up. However, the last scenario (WB4) is only partially correct...the white part. The black part should have been more darker. Is this a scenario where I am hitting the digital capability? Too much contrast?

Also, the EV was only -1/3! I would have under other circumstances, metered off the white and put that +2. (Should have done that in my test! dammit). I think I will have to re-run the test...arghhh.

Qarik

There really is no right or wrong here. The sekonic has no idea what you are shooting. It's a rule of thumb if you want white to look white the you have to over expose by 1.5 to 2 stops.

pathfinder

The correct exposure is the one that will give you a real white, a neutral grey, and a real black when printed on paper with your system.

White should read near 250,250, 250 ( R,G,B channels ) in Photoshop. Blacks down around 8,8,8. Greys should read about 130,130,130.

None of your whites and black really come very close. If your exposure is off, your color balance will be off too, if you are shooting jpgs. A good, well exposed jpg of a grey scale step image, should contain a gradient of greys from black to white as described in this thread where I was talking about color balance tools, which means your exposure MUST be accurate within 1/3 of a stop.

I posted the image data of the whites, and blacks, and greys, so you can see what can be done with good exposures. The images were jpgs directly from my camera with no processing whatsoever.

To do this, your camera histogram needs to display a spike on the left for the blacks, a spike on the right for the whites ( but not blown out ) and a spike right in the middle for the grays. A shot of a correctly exposed, true neutral gray card, should be a single spike in the center of your histogram with the Red, Blue and Green channels all perfectly aligned.

I find to achieve the most accurate exposure, I prefer to turn off + and - EVs, and shoot in Manual Mode. That way I know exactly what my exposure was and how to vary it for a more accurate exposure, by examine my histogram, if I do not have a grey card to work with. An incident light meter can be a great help as well. Incident light meters do not worry about subject reflectivity, just light intensity.

Art Scott

Which Sekonic are you using and are you using as a reflected meter or as an incident meter??
This does make a real difference in what you get. In this respect it does not matter if using flash or ambient light......
There are lots of people that think an incident meter is only for flash...but it is actually the most accurate meter for
objects that can be metered with it.......ie...still-life's, portraits, weddings, but not landscapes or astrophotography or wildlife....

Hope this helps a bit..............

pathfinder

They used a Sekonic L358, Art, which is an incident meter, and, hence, should be very accurate. I agree that an incident meter is not just for flash, also.

wildviper

Well, I have question of this incident meter too...that is the other thing that has confused me.

At a school that I go to, the teacher mentioned that if the light meter reads X and you are shooting a white object, add EV +2(or thereabouts) since the lightmeter is calibrated to 18% grey! That got my head scratching since I figured that with incident meter, it shouldn't matter.

Came home and checked Sekonic's site..and found the opposite. Here ..so what gives?

I am going to re-run this exposure test...any other ideas on what I should do this time? I will post results here. Besides what pathfinder suggested.

ivar

wildviper wrote: »

At a school that I go to, the teacher mentioned that if the light meter reads X and you are shooting a white object, add EV +2(or thereabouts) since the lightmeter is calibrated to 18% grey!

I'm not sure what 'mode' you are in when using a meter, but I don't see the point in using a separate meter and a mode other than 'manual', I think.

If the meter says 1/125 and f/16 that's what you dial in. White or black. That's what the page you linked to above shows; regardless of the background, you get the same shutter & aperture.

If you don't have a lightmeter, and you are using your camera in for instance Aperture Priority mode, you can add +2EV for instance, to correct for the lightmeter 'being fooled'.

Art Scott

ivar wrote: »

I'm not sure what 'mode' you are in when using a meter, but I don't see the point in using a separate meter and a mode other than 'manual', I think.

If the meter says 1/125 and f/16 that's what you dial in. White or black. That's what the page you linked to above shows; regardless of the background, you get the same shutter & aperture.

If you don't have a lightmeter, and you are using your camera in for instance Aperture Priority mode, you can add +2EV for instance, to correct for the lightmeter 'being fooled'.

Exactly........it does have to be manual mode because if you are any other mode and change anything the camera will automatically change the one you did not.......................with an incident meter you should not have to dial in any exposure comp.......that is why I have used a handheld incident meter for over 30yrs now.......fire flash once ..and got it, as long as meter is turned on and set properly any way...........or in non flash mode just press button and go..........

Of course there is the extremely slight chance that your meter is bonkers or that your camera is off....as I said extremely slight is the chance.........


OOOOOOH are the batts in the meter new, old, sloightly used, been stored for quite a while......try a session with brand new (with a use by date several months or years down the road....) batts........

wildviper

Btw, the reason that I am using Aperture priority is to get a handle on how that mode works, especailly when I do wedding photography. I do use manual, but sometimes fast events dictate using AV. I want to know how to dial my EV based on what I am seeing and what the "correct" exposure is base don the light meter.

ivar

wildviper wrote: »

Btw, the reason that I am using Aperture priority is to get a handle on how that mode works, especailly when I do wedding photography. I do use manual, but sometimes fast events dictate using AV. I want to know how to dial my EV based on what I am seeing and what the "correct" exposure is base don the light meter.

Using Aperture Priority in combination with a lightmeter is THE way to get confused I think. You should get a good understanding of using a lightmeter in Manual first.

The lightmeter you are using gives you the correct aperture/shutterspeed because of the way it works. The lightmeter in the camera works in a different way and doesn't always get you the correct solution.

Richard had a nice way of putting it; the lightmeter in your camera wants to get everything neutral grey (that's what it is calibrated for).
So the camera sees the white plate, but wants to make it grey. How to get white grey? reduce the exposure --> the camera will actually underexpose. So to compensate for the camera making the plate grey you need to up the exposure (by adding +EV)

When the camera sees the grey plate, it will work like it should.

When the camera sees the black plate, it will also want to make it grey. How to get black grey? increase the exposure. So to compensate for that you need to decrease the exposure (by adding -EV)


So generally speaking you can say that if you are photographing something white (snow, for instance) you need to increase the exposure and when shooting something dark (black dog) you need to decrease the exposure.

wildviper

well my camera is in service..so I will do this again when I get it back.

pathfinder

I would suggest you learn to shoot the correct exposure in Manual mode. Once you can do this well, THEN, give Av with +/- EC a try.

Using exposure compensation will make more sense when you can set accurate exposures in Manual mode. I shoot Av fairly often, especially in fast moving, changing lighting situations, but I usually start in Manual to know where things need to be first.

Walk, before you run.

With Av or Tv, or P, you will have more variation in frame to frame images than in Manual mode if the lighting is not changing. Can you tell me why this is true?

wildviper

pathfinder wrote: »

I would suggest you learn to shoot the correct exposure in Manual mode. Once you can do this well, THEN, give Av with +/- EC a try.

...

With Av or Tv, or P, you will have more variation in frame to frame images than in Manual mode if the lighting is not changing. Can you tell me why this is true?

Yeah, I realize the variations. You asked me why(to check my understanding I believe). The answer is that it depends what is infront of the meter from scene to scene. If one scene was filled with people in dark suits vs the bridesmaid on the other scene wearing all bright colors..the exposure will be changed by Av/Tv or P..even though the lighting may not have changed much.

I think I will take your advice for a shoot that is coming up for me as a second shooter.

pathfinder

Exactly! The problem is that the reflected meter in your camera will adjust the exposure up and down "without your permission" depending on whether you are shooting a white dress or a black tux, even though the lighting did not change an iota. Shooting in Manual Mode takes exposure control away from the dumb meter in your camera and gives it back to you.

If you can beg, or borrow an incident meter, like a Sekonic L358 or others, give it a try and see how you exposures begin to stabilize and not vary from frame to frame, and your images begin to display real whites, and real blacks. ( ot just use the RGB histogram on your camera )

Once you can do this consistently, go back to Av when you need the faster speed it allows, and I think you will have better results with Av than previously. Av seems "easier" only if you are not really concerned about exposure accuracy. But wedding shooting demands a high degree of exposure accuracy to capture detail in white dresses and in black tuxedos as well.

Good luck!

takinmore

awesome
thanks pathfinder, I have been taking photos for a while now with my Nikon slr and couldn't understand why they would vary so much with the same light. I was shooting Av so i could manage the depth of field. Your explanation clears up a lot.

I'm going back to Manual like I used 30 years ago

pathfinder

Glad to help.