Confused about ISO

There are no real "limits". Not all cameras are equal. I can shoot 2,000 ISO with my D700 and get great shots. 400 ISO on a D70 and the image starts looking like garbage.
 
On the video that you posted, the sky is actually OVER exposed, and too bright to render much detail. Yes, a graduated ND filter would have been appropriate for that situation (like the first shot).

To start with, ISO is a quantitative measure of a film stock's sensitivity to light. It is now being used to express the sensitivity to light of digital imaging systems. For an over view, here is the Wikipedia article for film speed.

http://en.wikipedia.org/wiki/Film_speed

When you are shooting, with a specific camera, under specific lighting conditions, with a specific lens, you can control exposure by changing your aperture opening (F stop/T stop) your shutter speed, your ISO setting, or by filtration. Those choices, along with the use of supplemental lighting, camera angle, and camera movement, are the meat and potatoes of cinematography.

If you are using a T2i, which I have also recently purchased, you can use the camera's internal metering system to set your exposure. Now, I have a film background, so I am shooting with this camera at 24 fps, and I set my shutter speed to 1/50 of a second and will only change this with very narrow limits (1/60th or 1/40th, maybe). I also use manual focus, and manual exposure lenses. What I would do, in the situation that you have in the video you posted is to first set the camera metering mode to "Spot", then set the camera to the "M" mode, which is the still mode manual setting. Once I have set my frame, I select the area in the frame that I want to be the focus, put the "Spot" metering circle over that area and then adjust the aperture so that this area is exposed properly (the pointer is set to the middle). I then move the camera so that the "Spot" metering circle takes readings on all areas of the frame. I note what the change in exposure is for the different areas of the frame, and then do something about that.

The T2i has about a 7 to 8 stop useful dynamic range. I am still working on figuring out exactly what it is, at the different ISO settings, but if the different areas of the frame still fall within that, based on the readings from the manual metering spot readings, then I stick with the exposure of the scene focus, and set my aperture for that. If the frame has areas of light that are outside that dynamic range, then I have choices to make. I would need to use supplemental lighting, graduated filtration, or change the frame. Of course you could just go with it, and have a scene exposed like a home movie, or a reality TV show.

Once I have established my exposure, based on the meter readings from the "M" still camera mode, I switch the camera to movie mode and make my shot. Now, if you get down in it and have to make the hard choices, then, as a general rule of thumb, make your exposure decisions to make your scene focus, especially portraiture, correctly exposed.

Of course, when I use this exposure method, I am calling on years of experience which includes many years shooting film. As apposed to Chris, I am more oriented towards to making incident light meter readings. Switching to reflected readings, using the camera's internal system, is still a learning curve for me also. Of course, the system I described, is for run and gun, of other situations in which I can not control the lighting. When I control the lighting, I chose the lens (focal length), aperture, ISO and shutter speed first, and control the lighting to fit that. I haven't done it yet, but with the DSLRs, I will incorporate the camera internal metering, as a supplement to my use of an incident light meter to set exposure.

I use a Sekonic L-398, Studio Deluxe light meter. They are available for less than $200.00. It is an analog meter, and I guess I have had mine for almost 20 years now. I have always meant to get a more advanced light meter, but just never got around to it, since the Sekonic works just fine for me. While a lot of expensive light meters have a lot of "Gee Whiz" features, you have to realize that, what ever light meter you get, the most important thing it gives you is a point of reference, that you have to take and make creative decisions with. All of my exposure choices are based on my long experience with the Sekonic L-398. Chose a light meter, learn how to use it, and go out and make great images.
 
Ryan Patrick O'Hara said:
It's not the BEST thing to do when the money is on the table and the shot counts... but as far as learning, it demands more discipline and exacting knowledge to understand lighting and ratios without looking at a monitor.

But the downside, however, is that being this familiar with lighting is always a non-exact science, unless you work with the same camera all the time. DIfferent cameras have different ways of reproducing light via dynamic range, latitude, and color reproduction... therefore not only do you need very good knowledge of lighting but you need to have a very good knowledge of the camera you are using and how to light for it.
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I almost want to fight for the idea that even when money is on the table, you should probably ignore what the LCD is giving you. It's always always wrong in one way or another. Sometimes I wish my digital camera would just show me a big histogram, and only that everytime I took a picture, because I already know what's inside the frame, and I know if I expose it properly, everything will be fine.

It's true though, to believe in this idea you have to know the camera and have seen what happens in different situations and different results.

Read Ansel Adams "The Negative", that will get you brain workin'.
 
RyanT said:
I almost want to fight for the idea that even when money is on the table, you should probably ignore what the LCD is giving you. It's always always wrong in one way or another.
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This is why I miss film. It was SO much fun to take my new FILM camera out a few months ago and just shoot. Use your experience, skill, and craft... and just pop the shutter. Getting it back after development and seeing your work is just magical.

But then I started on a Anscomat rangefinder film camera. Not sure how many here are even old enough to remember rangefinders. I probably shot for 7 years before I held my first SLR. I had a 110 camera, a 126 camera, and that 135. All before seeing an SLR.

We've come so far in some ways, and taken some major steps backwards in others. People look at the LCD in these HDSLRs like they were calibrated monitors or something. When really, it's more akin to a sophisticated video tap. I don't trust them for anything.

When I shot a night soccer game last winter on my friends 50D, he had to remind me that I could use live view. I told him I preferred the optical and stayed with that. Different generations for sure!
 
perroneford said:
firstly, i do not mean this response to sound harsh in any way. I have a lot of respect for people who are trying to learn this stuff and are willing to ask questions to improve their work.

That said, more than anything else i've noticed about the dslr revolution, is that it's showed up and exposed shooters who have no background in photography. I would estimate that 90% of the questions we see regarding shooting with the cameras are things that are covered in a first year photography course.

As dadinwinchester has noted, the answer here is a light meter. But that is hiding the point. The point here is that there is a general lack of understanding of exposure and the relationship of iso, shutter speed, and aperture.

To the original poster i would strongly suggest two courses of action.

A. I would suggest signing up for a photography course at your local community college. Everything you learn there will apply directly to video. It will answer a great many of your questions and give you a wonderful level of confidence behind the lens.

B. I would suggest spending some time on your own taking photographs. Treat the camera as though it had film in it. Iso 100, iso 400, iso 800. 100 for outdoor sunny conditions, 400 for outdoors without a lot of sun, or well lit indoors, and 800 for indoor with natural lighting, or outdoor evening. Then go through the apertures and see what you come up with. Take notes, or i guess you don't need to do that now since we have exif data. Sorry, i grew up with film!

These exercises will cost you nothing. When i learned, it costs hundreds if not thousands of dollars in film and processing.

And if you continue to shoot on a dslr, buy a light meter. The sekonics are excellent as are the spectracine units like i have, and that one's a bit cheaper though not as fully featured.

Best of luck to you.
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+1
 
Halsu said:
Technically, yes. In practice, the current sensors have so low a noise that upping ISO is not nearly as big a problem as it used to be.
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Yes, it has come a long way, that is for sure, but on the T2i, I personally find the noise above 800 ISO to not be pleasing at all. I realize that in some situations that you have to do what you have to do and have to go higher, but I am going to try very hard to stay at 800 ISO, or less, with THAT camera.
 
digifruitella said:
http://www.youtube.com/watch?v=ac3KbmiLEho

as you can see in the first shot, the sky is underexposed - I take it I needed a gradual density filter here...
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As others have said, the sky is overexposed, not under. And yep, a gradient filter would have helped.

As far as the exposure goes, in general i personally try to follow the ETTR priciple (Expose To The Right). In other words, expose as bright as possible, without clipping highlights. I don't know if your camera has a feature that shows when the image is clípping to white (i.e. blinking black on top of the highlights, or a zebra pattern), but the proper exposure using this technique is just before anything important hits that.

I also shoot (almost) as flat (low contrast) images as possible with any given camera. I'm not familiar with your camera, but you probably have picture styles to choose from, maybe "neutral" or similar might work here. Or, you may be able to use custom styles. The resulting images aren't necessarily too hot as-is, they often/usually need to be color corrected to get the final image to look pretty.

Here's a pretty good video about it.
 
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David G. Smith said:
Yes, it has come a long way, that is for sure, but on the T2i, I personally find the noise above 800 ISO to not be pleasing at all. I realize that in some situations that you have to do what you have to do and have to go higher, but I am going to try very hard to stay at 800 ISO, or less, with THAT camera.
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Well, even that's quite a lot actually, assuming the native ISO is 100 or 200: 2 or 3 stops, or 12-18 dB in video camera terms.
 
cardmaverick said:
The zone system is based on using a reflective light meter. If I remember right, the Ansel Adams book I learned it in was quite critical of incident metering. I can somewhat agree, though incident metering does have its uses for more advanced light meter users.
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The 'zone system' hinges on 'what you see (through a Wratten 90 filter...) is what you get'... or perhaps 'what you would see, is what you can achieve'...

But basically the idea is to know the film+processing+printing response, and a priori 'map' what is currently seen in the setting, and make those values represented in the final print. There are an additional 'requirements' often stated, such as 'detail' in the whites, 'detail' in the blacks... etc... but if your 'intent' was to have a blank white sky... or blank black shadows... well that was your intent...

So, in order to be able to 'map' scene values into final print values, one has to know what the imaging material+processing is capable of... If an object is 'reflecting' X amount of light, then the lens+sensitive material should be exposed to render 'reflecting' X amount of light as desired in the final print...

The 'problem' with incident meters, is they do not indicate what the 'reflected' light value is that is 'seen' by the camera and sensitive materials.

There's even a debate about 18% grey... is it really 18% or something else...

So, most of the Zone System is 'calibrating' the materials and processing to how a particular photographer 'works', rather than relying on manufacturer's data, or 'standard estimates of reflectivities'...

Using a spot meter one can determine the relative reflectivities, and resulting 'required' exposure.

One of the significant differences in still shooting and 'film' is the fact that for film, one is typically limited to 1/50 or 1/60 shutterspeed for a 24 fps filmspeed. Hence, one has only aperture, neutral density, or ISO to change to achieve a given exposure.
Or, if the light is too low... learn to love digital 'grain'...

As a note, I believe there is a significant technical difference between the way in which 'digital' ISO numbers are determined, vs. Real(tm) Film.

For Real(tm) Film, it is based on the amount of light required to result in a density of .01 above 'filmbase+fog' on the film.

There are several 'measures' for the digital equivalent of ISO, and so, one is not left with a certain sort of 'absolute', as in the case of Film.
 
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My personal approach to metering is to set my meter up for overexposure compensation, and simply meter off the scenes brightest object. Works every time! I do use a zone system inspired method myself, I just choose to work from the top down instead of the middle down - because unlike film, digital sensors have a hard upper limit you need to protect.
 
cardmaverick said:
My personal approach to metering is to set my meter up for overexposure compensation, and simply meter off the scenes brightest object. Works every time! I do use a zone system inspired method myself, I just choose to work from the top down instead of the middle down - because unlike film, digital sensors have a hard upper limit you need to protect.
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That's the 'recommended' way, for digital and it has been recommended for slide film as well. Because the highlight detail is 'lost' quickest/first...

In the case of B&W negatives, one could always 'futz' around with development times to either get the 'best' density for 'highlights' in the eventual print, or 'save the day' if the negative was under exposed, and live with the resulting grain of 'over development'...

Slide film always required much more care in exposure, and was not really amenable to the changes in processing to compensate.
 
j1clark@ucsd.edu said:
That's the 'recommended' way, for digital and it has been recommended for slide film as well. Because the highlight detail is 'lost' quickest/first...

In the case of B&W negatives, one could always 'futz' around with development times to either get the 'best' density for 'highlights' in the eventual print, or 'save the day' if the negative was under exposed, and live with the resulting grain of 'over development'...

Slide film always required much more care in exposure, and was not really amenable to the changes in processing to compensate.
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Yeah, the first film I shoot was reversal film, and I think that getting used to that has served me well with the switch to digital/video, as exposing them is very similar, i.e, expose for the highlights to avoid over exposure. Compared to reversal film, exposing color negative is easy... expose for shadow detail, and all is well. (a broad generalization, of course)
 
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