How To Get Consistent Results With Your Histogram (Camera Lesson 30)

Summary: For those times when you’re stuck using your camera’s histogram- here’s how to get consistent results for images in your film.

Length: 2:49 minutes

Video Lesson

Transcript

Introduction

As I demonstrated in the previous video, histograms are the least helpful exposure tool that you can use. But sometimes for whatever reason you just can’t avoid it and you have to use the histogram to judge your exposure. In this video I’m going to show you how to use the histogram to get accurate exposures that will produce more reliable results then using ETTR (Expose To The Right) or ETTL (Expose To The Left).

The Problem: It’s Content Dependent

Histogram Problem: ETTR & ETTL - (Camera Lesson 30) [VIDEO SCREENGRAB]

So the problem with ETTR and ETTL is that it is content dependent. As soon as your framing changes the amount of highlights change, and your exposure changes accordingly. So you need to have a system that is not dependent upon highlights.

The Solution: The 18% Gray Card

Histogram Solution: 18% Gray Card - (Camera Lesson 30) [VIDEO SCREENGRAB]

And that is where this tool comes in handy. This is an 18% gray card. And you can pick this up from Film Tools, B&H photo, or Amazon for about $20 for 2 of them. Another option would be to use the DSC Labs One Shot Chart. At just under $300, this chart is spendy, but you can use the other side to provide an accurate reference that you can color grade to.

Histogram Solution: One Shot Reference Chart - (Camera Lesson 30) [VIDEO SCREENGRAB]

This gray card represents middle gray, or your mid tone values. So if it is exposed properly, it should look like a gray card in you scene (surprising I know). And this is the tool you will use to ensure your exposure remains consistent.

Placing 18% Gray Card - (Camera Lesson 30) [VIDEO SCREENGRAB]

To use this gray card, what you want to do is to place it in your key light, and make sure it is as evenly lit as possible. Realistically when you are out on location, you’ll never be able to have it perfectly lit- so just get it close is enough. Often times you can just rotate or tilt the card so that as much of the light as possible is hitting it.

Placing 18% Gray Card to fill screen- (Camera Lesson 30) [VIDEO SCREENGRAB]

Now you’ll take your camera and fill your frame with the card- edge to edge. You do this just to make your life easier. Unless you fill the frame with the card, it can be hard to tell where the card falls in the histogram. Now you adjust your exposure until there is a sharp spike in the center. If you happen to be using a DSLR, then you can use the exposure meter on the back of the camera as a second reference point. The little arrow, or flashing block, should fall under the 0, or very close to it on either side.

Placing 18% Gray Card creates peak on histogram- (Camera Lesson 30) [VIDEO SCREENGRAB]

After you have achieved that exposure, you are now set and ready to roll. When you change shots or framing, as long as that gray card still falls in the middle of the histogram, you know that your exposure levels are the same. If you change shots and the card no longer falls at the same exposure level, then it is time to adjust your lighting.

Thoughts?

So that is how you can use your histogram to get an accurate exposure, and maintain consistent results regardless of the composition of your frame.

If you have any comments or questions, leave them in the comments section below, and then come join me in the next video.

Depth of Field, Part 1: How Aperture and ISO Affect Focus

price76 says:
March 8, 2015 at 9:46 pm

Hi Ryan,

I’m a little confused regarding the middle grey calibration more specifically in relation to DSLR cameras which seem to put middle grey at 40-45 IRE(I am using a 5dmkii and 7d and seem to be getting 45 IRE when I follow your above advise and use the in-camera spot meter to be bang on 0, or zone V off 18% grey card, also my exact IRE readout for middle grey came from using the magic lantern spot meter in IRE mode once I had got 0 on the in-camera spot), so when I do this of course the histogram reading is slightly to the left of middle as one would expect. My first question is (after that convoluted explanation) do I run with using 45 IRE as middle grey or bring up my exposure to 50 IRE for this calibration from the key light source? If not and I set middle grey to 45 IRE are my IRE target values you discussed (skin tone and all the others) needing to be all brought down by 5 IRE?

thanks
Dave
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- Ryan E. Walters says:
  March 9, 2015 at 9:03 am
  
  Dave,
  
  Great observation. 🙂 And here is where artistry, personal preference, and scene content come into play. You can go with 40 IRE, 45 IRE, or 50 IRE- it is up to you. Regardless of which one you choose, just stick with that reading and you’ll get consistent results with your histogram / waveform.
  
  If you choose 40 IRE:
  You’ll be very slightly underexposing your image. (Maybe by 1/3 – 1/2 of a stop at most.) What that means is that there will be more room in the overexposure part of the image (See Lesson 28: Properly Exposed & Lesson 32: Advanced Exposure.) So your highlights will roll off more smoothly- they will not clip as fast or as harshly. However, if you want to bring up the levels in the grade, the mid-tones and the shadows will be more noisy- which may be objectionable to you. Depending on the look you are after, 40 IRE would probably be a better choice for a scene with a lot of highlights. (Zone 9 & 10)
  
  If you choose 45 IRE:
  You’ll be ever so slightly underexposing your image (or it may be spot on) by about 1/3 of a stop or less. Same rules apply as the 40 IRE exposure, only there will be less room in the highlights, so they will clip faster, and not roll off as smoothly. Again, depending the look you are after, 45 IRE would probably be a good choice for a scene with some highlights. (Zone 9)
  
  If you choose 50 IRE:
  You’ll be either “correctly” exposing your image, or very slightly overexposing your image by about 1/3 of a stop or less. In this case, your highlights will clip faster, and not roll off as smoothly as 45 or 40 IRE. However, your mid-tones and your shadows will be cleaner then if you had used 40 or 45 IRE. So, depending on the look you want, 50 IRE would probably be a good choice for a scene with little highlights in it. (Zone 9)
  
  What if you like 40 IRE, and you want clean mid-tones & shadows?
  Well, that is where you’ll have to do some additional lighting, and our Lighting Series comes into play. 🙂
  
  As you can tell, there is just as much personal choice as there is technical “correctness”. The technical level is a good place to start. But don’t get hung up on just the technical- the look of the image and what you are after is just as important.
  
  I hope that helps.
  
  Cheers,
  Ryan
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price76 says:
March 9, 2015 at 4:31 pm

Hi Ryan,

Makes perfect sense 🙂

Thanks
Dave
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Mike says:
April 16, 2015 at 1:27 pm

This technique would give you the same exposure as taking an incident reading under your key light and setting your aperture to what the meter tells you, correct?
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- Ryan E. Walters says:
  April 17, 2015 at 9:32 am
  
  Yep, it gives you the same exposure as using a light meter. My preference is to always use a light meter, but I know that’s not everyone’s thing- and this trick works just as well.
  
  (Technically you are still using a light meter with this trick- you are using the light meter built into the camera. 🙂 )
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