Exposure Basics, lesson three?

Started Mar 18, 2013 | Discussions thread
Najinsky Veteran Member • Posts: 5,739
Re: Quick correction.

richarddd wrote:

Najinsky wrote:

richarddd wrote:

Dennis wrote:

richarddd wrote:

The more light on the sensor, the less noise but more possibility of blown highlights. Aperture and shutter speed (and available light) control how much light falls on the sensor.

I don't think I'd talk about it in terms of possibility; that suggests a randomness to something that you should strive to control. More light on sensor means less noise; too much light on sensor means blown highlights.

Of course, but I was pointing out the main problem with the wired.com triangle, which didn't even mention blown highlights. It also doesn't mention diffraction as aperture decreases. It both ignores some trade-offs and gets the noise / light trade-off wrong.

It's a recap aid about what the three settings are, in a bit more detail the the introduction aid. Not the exposure bible.

All that stuff gets covered in the course, just not all using that one slide.

Seriously, how sensible is it to judge a whole course on one slide and your assumptions about how it might be getting used?

The slide does not appear to add anything to understanding. Why use it?

I can only give the same answer I already gave to the same question.

The exposure triangle is useful in overcoming the new student's fear of the camera controls. At the introductory level of the students I was teaching, most had a fear that they didn't know what the camera controls were or how to use them. Most were shooting auto, all were shooting JPEG, even though some had DSLRs.

I would say to the students, when you shoot the camera in auto, the camera is making decisions for you about three key settings. What we're going to do is learn what those settings are, and what they mean to the camera. We'll learn how they impact your images so that we can begin to make our own decisions about those settings so we can start capturing the images we want.

This diagram shows you the three settings the camera is deciding for you (cue the exposure triangle diagram). Lets look at each one in turn.

And as also said elsewhere, this slide is a tiny section of the course. All the important explanations were covered by their own slides and lots of image samples. Followed by lots of practice and assignments. The slides had a small, but useful role.

On my camera, I can get lower noise (read noise) by increasing ISO, at least up to about ISO 800 or 1600. How does that fit into the slide?

It doesn't. But nor is it typical, and even less so when this course ran.

If you're going to talk about noise, why not say that more light on the sensor means lower noise and both aperture and shutter speed control light on the sensor? It's not a very complicated concept.

I did. And I already said I did in the main post :

I talk about the days of film, and show some old Olympic photos capturing action in grainy black and white. I mention that they used 'high speed' film which is more sensitive to light and therefore allowed them to get by with the available light/aperture and required shutter speed. I also explain how the picture is very grainy and this a consequence of having used less light.

Then I come back to digital and talk about the sensor. I explain that it's sensitivity to light doesn't change as was the case with different film speeds, but it tries to simulate this by boosting the recording to make it look like there was more light captured than there really was, to prevent the image from looking under-exposed. However, like with fast films, there is a consequence to using this.

This is what I mean about making assumptions about how the slides are used, even though I took the trouble to write about how they are used.


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