Exposure and a few other queries

[bagopeas]

Hi all,

I have a few questions that i need answered as part of this photo course that i want to do. I'm hoping to improve way beyond my amateur level.
Searched google with no luck so maybe you guys can help.


- When using both color negative and transparency films, do we work out the correct exposure the same way, if not why?

- Any disadvantage of using a telefoto lens?

- What happens to film if subjected to a magnetic field?

- What is a quick way to color correct an image containing a white or grey area?

- What is the maximum value of a pixel?

- What happen to a selection, made in a new TIFF file, if you were to press 'Backspace or choose Clear?'

- What happen to a selection, made in a new PSD file, if you were to press 'Backspace or choose Clear?'

thanx in advance, appreciate your help!

[Ben Syverson]

What a weird collection of questions.


- When using both color negative and transparency films, do we work out the correct exposure the same way, if not why?
This is aesthetics. Some people slightly overexpose E6 to open up shadows, some slightly underexpose to protect highlights. There are literally entire books written about how to expose negatives -- without knowing what you're trying to do technically or aesthetically, it's impossible to advise.

With that said, many people rate negative film slower than its nominal speed. It has so much latitude that it can take the overexposure and retain highlight detail.


- Any disadvantage of using a telefoto lens?
I'm going to gamely assume that you mean a LF lens with a telephoto design. As far as I know, there are no significant disadvantages to these lenses, and they let you use focal lengths that would be impossible to achieve on some cameras.


- What happens to film if subjected to a magnetic field?
Nothing


- What is a quick way to color correct an image containing a white or grey area?
Use the white balance color picker in Adobe Lightroom or Aperture. Not much use for color correcting color negative film, but you said "quick"


- What is the maximum value of a pixel?
In a typical 8 bit image, 255. In 16 bit, 32767. In 32 bit float, it's not a concern.


- What happen to a selection, made in a new TIFF file, if you were to press 'Backspace or choose Clear?'

- What happen to a selection, made in a new PSD file, if you were to press 'Backspace or choose Clear?'
Deleting a selection from the "Background" layer will fill the selection with the background color.

[bobwysiwyg]

Remember, it's Sunday. I think you just did his homework assignment and it's due tomorrow. :D

[bagopeas]

bensyverson: thank you, appreciate your help.

bobwysiwyg: haha, good one! except this is no school assigment. im applying for this intense photography course to really push my photo skills and for some reason they gave me this questionnare with a bunch of random Qs. Most ive managed to answer but these were the ones that left me totally confused.

There is also another i forgot to include:

- Name the most important part of the computer interface when working with the digital image, and say why.

( i want to say screen, but im not sure what they mean by computer interface)

thanx again all.

[Ben Syverson]

Remember, it's Sunday. I think you just did his homework assignment and it's due tomorrow. :D
D'oh! Well, if it's a take home quiz it's a gimme anyway. :D

[John T]

If they are asking these questions before you start the program, it seems like they just want to know where you stand. If other people supply the answers, it will skew the results and may not give them an accurate picture of your base knowledge.

That said, some of the questions are a little vague and questionably written.

[Alan Davenport]

- When using both color negative and transparency films, do we work out the correct exposure the same way, if not why?

For an "average" scene, and given negative and trans. films with the same ISO, the correct exposure would be the same. More or less. But the critical exposure for a negative is the shadows, while for transparencies the critical area is the highlights.

With negatives, there is a certain level of exposure below which you get no added density in the negative. If your shadow exposure is not sufficient to get past the toe of the density curve, then those areas will be nothing but the clear film substrate after development. Such areas are what we call blocked shadows.

In transparencies, the case is reversed. An overexposed highlight leads to the same result -- areas where all you have after development is the clear film substrate, with no density built up in the emulsion, AKA a blown highlight.

So for critical exposure calculations, you need to use opposite ends of the brightness range. For negatives, you should meter the darkest shadow where you require usable detail in the final print, then place that exposure on Zone III or perhaps Zone II once you know how the film responds to your development and printing workflow. For transparencies, meter the brightest highlight where you need to retain detail, and place that on Zone VII.

You can only place one value; all other values will fall onto the exposure latitute of the film depending on film type and development.

[Alan Davenport]

- Name the most important part of the computer interface when working with the digital image, and say why.

Make sure the mouse and keyboard (or other input devices) are securely tightened. There's nothing worse than a loose nut with a computer. :)