I hope this post is not entirely irrelevant since Gio Scope was released about a year ago. Despite arriving late to the party and with everyone already departed I want to provide a more coherent criticism of Gio Scope than has been offered online. After all, the Red forum addresses all questions in the same manner in which buckshot addresses a target; demolishing it beyond all recognition. In comparison I will handle it so exhaustively as to produce somnolence in the reader.
I was unaware of the existence of this tool until I had dinner the other evening with a former student and now colleague. We are trying to work on applying the science of sensitometry to digital cameras in order to update the technical foundations behind Zone System. He showed me the post on No Film School which claims that Gio Scope “works just like Zone System.” Being a Zone System practitioner with my analog photography and using its principles on set as a cinematographer I wanted to pursue this claim to both better understand the tool and clarify the practice of Zone System for myself.
The Tool
Gio Scope is a false color view overlaid on the RAW sensor data. I am assuming this tool works on the RAW data post linearization but pre white balance and debayering. Since Gio Scope views the RAW image the advertised 16 stops of dynamic range of the sensor are broken into 16 steps, each corresponding to one stop change in light intensity in the scene. These are numbered from 1 to 16 with the noise floor being below 1 and full well capacity as above 16. (For the sake of avoiding confusion I’m going to refer to the Gio Scope divisions as steps and the Zone System’s divisions as Zones.) Since the tool correlates exposure to each numbered step Red proposes this as a substitute for a light meter.
When the cinematographer selects the numbered zone on the scale at the top of the screen the corresponding area of tonality is filled in with a unique color in the image. I particularly like the feature of selecting the specific tonality shown in false color because this greatly simplifies the information viewed and can be tailored to an individual’s lighting process. Moreover, the selectivity feature also allows the user to quickly analyze the contrast ratio between any two selected steps.
So does Gio Scope work just like Zone System?
In honesty, I cannot find anywhere that Red claims Gio Scope replaces or has anything to do with Zone System on their website or in the video introducing the tool. The claim seems to originate on the No Film School website as the tool “working just like Zone System.” Of course, this statement has been picked up by Red users and discussed on their forum. The first post not only astutely inquires as to the relevance between Red's tool and the Zone System, but also links to Norman Koren’s website who I personally find is a venerable source of answers. Despite Norman’s lucid explanation I can understand how confusion is created from the differences between the Gio Scope 16 step scale and the Zone definitions.
Opposing Scales
One of the first points of confusion is attempting to correlate the 16 step scale in Gio Scope to the 11 Zones in Zone System. The difficulty primarily lies in the numerous ways in which the two could be related. For instance, if we relate each step to each Zone in a 1:1 manner than we have two seemingly arbitrary scales of numbers. Where do they connect in a comprehensible manner? Red reports that step 11 is neutral gray so using this as Zone V we could produce the following chart:
However, this only brings up multiple questions. What use are the Zones below 0 and are they superfluous? Why is the neutral gray point on the Red sensor not 8.5? What ramifications does this have to image quality assuming I have even more Zones below 0 and I consider them as part of my exposure?
Tying the Zones to the steps in this one stop correlation is problematic because Zones can be more or less than a stop of exposure because they are defined perceptually. At this moment I recommend looking back at Norman's website and reading the Zone definitions as supplied by Ansel Adams. So under this logic I should actually look at the RAW image and assign the tonality I see to each corresponding Zone. In which case it would look something like this:
Relating the Zones to the RAW image is a conceptual dead end because the desired end of photography is to relate tonality as seen in the world to that of your final image. If one decides to light a scene such that the RAW view appears to have Zones from 0 to X then the actual scene would look very unusual and very high contrast! Attempting to correlate the RAW image to each Zone is as foolish and unnecessary as the analog photographer looking at his negative and trying to do the same.
Linking the Zones to these 16 steps fails because the Zones and their definitions are conceptual tools. As Norman Koren points out on his webpage the Zone definitions embrace each step in the photographic process whether the scene, the print, and the different gamma settings of computer monitors. In the highly technical but unparalleled Beyond the Zone System Phil Davis further frees up the definition of a Zone by calling it “An ambiguous term” in the Glossary. While Davis does continue to clarify his definition what I wish to emphasize is that these Zones are tied to a conceptual division of the range of black to white with neutral gray as the midpoint of the scale. Since we like decimal scales there is something not only appealing but intellectually useful about having a ten step scale balanced around Zone V. This is entirely different than the steps in Gio Scope which are tied to camera data and therefore serve cannot serve the same purpose.
Zone System is more than just the sum of its Zones
Defining Zones perceptually allows the photographer to understand the changes in tonality through different mediums and through each step in the imaging chain. In order to make this clear it helps to look at the definitions of Zone System by multiple experts.
Ansel Adam’s own definition from The Negative: "The Zone System allows us to relate various luminances of a subject with the gray values from black to white that we visualize to represent each one in the final image. This is the basis for the visualization procedure, whether the representation is literal or a departure from reality as projected in our “mind’s eye." After the creative visualization of the image, photography is a continuous chain of control involving adjustment camera position and other image considerations, evaluation of the luminances of the subject and placement of these luminances on the exposure scale of the negative, appropriate development of the negative, and the making of the print.”
Similar definitions emphasize the interconnectedness between each step of the imaging chain and that its ultimate end is the realization of the photographer’s artistic vision. Notice that this last definition does not even need to address camera technology.
From White, Zakia, Lorenz’s seminal The New Zone System Manual: “Previsualization is the beginning, control of the process the middle, and postvisualization brings the process full circle.”
The use of Zone System is often best understood through a test shoot and there is an extremely helpful video here that was originally made to demonstrate Gio Scope.
The image in this video has nearly a full range of tones from black up to nearly a pure white. The subject’s face is lit with a 4:1 contrast ratio and the RedGamma4 curve is applied. Watching the overexposure of our subject’s skin you can see that at the image is completely blown out at step 16 which indicates this is 5 stops overexposed. This is Zone X! As the camera stops down you can see that the highlight side of his face just begins to possess detail when it reaches step 14, which would be analogous to Zone VIII.
Moving forward you can do the same analysis for the shadow detail by observing the fill side of the subject’s face fall into underexposure. Notice that when the fill side is at step 8 the exposure is such that it has just enough visible detail before being plunged into black when exposed at step 7. This means step 8 correlates to Zone II. My reason for picking out Zone II and VIII is that these Zones are critical because they contain the deepest shadow and the lightest highlight that still contain texture and detail in the subject. Therefore, if I want any information about my subject present in the final image I need to light, expose, and control my post process so that it fits within this range of Zones.
What is particularly good about this video is that it provides useful information to the Zone System user; RedGamma4 is a curve with a correlation of one stop of exposure to each Zone. Any exposure in my scene above or below 3 1/2 stops will not be reproduced in the final image. To see this in an analytical setting I exposed a gray card at subsequent steps of over and underexposure and charted the results:
Data produced applying a simple Zone System test designed to the Red Epic. Side note: despite setting exposure through a light meter the image came back 2/3 stop underexposed and I lifted the curve appropriately. I have found this is pretty consistent with most digital cameras due to the way the manufacturer maps their curves but also that when the scene is lit with a tungsten light there is exposure loss from the reduced spectrum of the source.
With this graph you can visually see that the last points of useable tonality that are above Zone VIII and below Zone II.
If I wanted to translate Zones into the steps in Gio Scope I could claim that the RedGamma4 has a range of steps 6 to 16 to create a black to white image and that the useable range of tonal detail is from 8 to 14.
The fact that RG4 correlates so nicely to the Zone System definitions and each Zone is a whole stop change in exposure is because the camera image with this gamma holds a 7 stop SBR or Subject Brightness Range. SBR is a Zone System acronym used for the range in subject brightness from the limits of tonality with visual detail, in other words from Zone II to Zone VIII. When this range fits the limits of the photographic medium and its display (camera + monitor or camera + print) than the final image will depict a full range from black to white tonality. As you can see in this video this is exactly the case when the exposure is correct, which is about at the 0:20 point when the key is in step 11 and the fill in step 9. On our curve the SBR would be represented as follows:
Since my exposures are in the middle of these Zones I have a 1/2 stop range in exposure above and below them. I should say the limits of my scene are 3 1/2 stops above and below normal exposure and this gives us the full 7 stop SBR.
At this moment it is worthwhile to re-visit Phil Davis definition of a Zone in its entirety:
“An ambiguous term. In this book, any one of the several divisions of the print gray scale that represent separate, consecutive luminance ranges of 1 stop in the normal subject. In subjects other than the normal 7-stop range, each print zone represents one seventh of the total SBR, whatever it is. Print zones stand for specific average values of gray that, when memorized, assist the photographer in visualization.”
Quite a few comments on the Red Forum and many on the internet make the claim that each Zone equals one stop. This can be the case in the special circumstance where the SBR is 7 stops and the photographic process places this SBR in Zones II to VIII in the final image. This is about the range of an average scene and I would like to reserve a further discussion on this point for a future post because there are important ramifications here for understanding the limits of our visual system as well.
Nonetheless, if the SBR is less than 7 stops than we are observing a low contrast scene and if higher than 7 stops we are observing a high contrast scene. (Of course, there is a level of subjectivity in what is high or low contrast, but this is a rough mathematical definition.) In these instances the photographer changes their lighting so the scene better matches the limits of their medium, or perhaps changes their development time of the negative or the shape of their curve in Photoshop to produce a final image with full black to white tonality. In this instance each Zone in the scene is expanded or contracted to produce a full black to white final image. The fact that Zones are not precisely tied to each stop of exposure is why the System works so well: the scale of tonality needs to be flexible because it is being transformed by the medium at each step of the imaging chain. This is in direct contrast to the rigid Gio Scope scale. If a step in Gio Scope can be white, neutral, or black depending on the LUT applied then it becomes irrelevant data.
Even though I have given correlating numbers between Gio Scope steps and Zones the entire use of the Gio Scope scale is unnecessary. Zone System encompasses the entire process whereas Gio Scope is confined to analyzing one step, the exposure as seen by the camera. In which case Gio Scope as a tool only has two functions; seeing where the exposure falls in relation to the sensor in order to ensure it is not beyond the limits of the camera’s dynamic range, and as a light meter if none is available.
If not a Zone System how about a Zone System Tool?
Investigating Gio Scope's use to a Zone System practitioner is also best handled through an example. Consider the problem of creating an image of a black and white cat and you want to determine the exposure of his white and black fur. To find this you must press the individual steps on Gio Scope until the white and black fur are shown in false color. Compare this to aiming and pressing the button twice on a light meter. Obviously, the light meter is a much quicker method by which to acquire exposure information. I could additionally argue that looking at a Waveform would be quicker as well. (If Gio Scope was to function with the speed of a light meter it would need to be programmed so that the user could press an area on the image and all corresponding tones were shown in false color and the step in the scale above is highlighted. That would be an impressive feature!) True, Gio Scope is helpful in determining that if the white fur is in step 15 and black fur is in step 5 then our subject has a contrast range of 10 stops. However, you could also just know your f/stop scale and that the difference between the metered dark fur at f/1 and the white fur at f/32 is also two stops. If the latter seems more difficult than this probably is because you are not engaging with the f/stop scale as much as you should.
The second problem that would be worth investigating is that most false color modes highlight not a single exposure, but a range. So each step most likely highlights a range of one stop of exposure. This could lead to a false impression of a scene's contrast range. If the cat’s fur is on the cusp of steps 4 to 5, just barely in 5 and at the cusp of 15 to 16 and just within 15 then it would be better to interpret this ratio as 11 stops. I think this is especially critical in the interpretation of contrasty scenes that push the limits of your medium. I understand that RAW allows for correction of exposure errors, but this becomes increasingly difficult at the limits of a sensor. Moreover, whether the tonality is rescued from over and under exposure successfully is dependent on so many circumstances and upon the desired quality of image that I would rather not pretend a 1 stop difference in exposure does not matter.
So I contend that using a light meter is far simpler. If you know your shooting stop than it is really just a matter of taking readings of objects and seeing if they fall into the Zone of your choice. The No Film School article suggests that in order to do this you also need a pencil and paper, but this is maybe only the case when first practicing Zone System or if you are rigorous and take notes on set. However, this notion that Gio Scope liberates you from having to use a pencil and paper are the kinds of comments I find commonly made by those who do not practice Zone System but like to provide criticisms from their lack of experience. Some photographers write down exposure info and its relation to Zones and some don’t. That’s an individual’s working method and has nothing to do with Zone System itself.
What Function Does Gio Scope have?
Zone System is a method by which a photographer can envision an image and knowing the limits of their medium reproduce their pre-visualized tones in the final image. This is a world of difference from Gio Scope which is just a new variation of a false color view using the RAW sensor data. Zone System encompasses the photographic process whereas Gio Scope is an exposure tool. Calling Gio Scope a Zone System is enthusiastic fan-fiction that misrepresents both. Certainly, it could be a tool used by someone using Zone System in their work, but only in the limited capacity of a means to analysis exposure on the sensor. Does Gio Scope replace a light meter? Not entirely, as a light meter could be seen as a quicker and more accurate tool.
I am not saying that Gio Scope is not useful, but it is not novel. Perhaps this explains the confusion expressed by so many users when their experience of this tool does not correlate with what they are being told about the tool. One user on the forum glibly offers that this is what happens in the face of innovation. I hesitate to go as far in this case because I don’t want to mistake change with innovation. Sometimes change is innovation but more often change is just change. We need to always be wary of change masquerading as innovation.