How to calculate average speed.

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Chan Tran

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I really don't want to say how one should use the meter and arrive at the exposure he/she wants. I simply first show the OP how to calculate the average of several spot readings in the fashion that a meter with that function would do. I don't say it's a good or bad approach. I did make a comment that if you average a lot of readings then you come up with the same reading as if you use a wide angle averaging meter instead of a spot meter.
 

markbarendt

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I really don't want to say how one should use the meter and arrive at the exposure he/she wants. I simply first show the OP how to calculate the average of several spot readings in the fashion that a meter with that function would do. I don't say it's a good or bad approach. I did make a comment that if you average a lot of readings then you come up with the same reading as if you use a wide angle averaging meter instead of a spot meter.

I was probably reading to quickly and to quick on my comment, no offense meant to you or Bill.
 
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Absolutely and as you point out the fix required is often a change of lighting, whether artificial or natural.

I will suggest though that this problem is common to all photographic mediums, the problem with slide film is that the fix has to be applied during the camera exposure because we are going straight-to-final-output. With negatives we can change the scene lighting or we can burn, dodge and manipulate when we print, or both.

This isn't necessarily the case, in fact Dunn and Wakefield essentially puts pegging to the shadows into more of a special-case-use classification in the grand scheme of photography. It's basic advantage being minimizing exposure, which is nothing to sneeze at, but not necessarily a priority for most shooters.

Personally I no longer peg any exposure to shadows, my choices are always centered on the mid-tones I want to print, shadows and highlights are simply allowed to fall around that come what may. I will on occasion use a high tone and an offset to peg my mid-tone. I avoid using shadows as a peg because I find judging them unreliable.

Onward, I'm not understanding what extra limits you see with color negatives, can you elaborate?

Gladly Mark :wink:

My observation that color negative film has more limitations is simply that color film cannot be developed to such different extremes as black-and-white negatives; no N+2 or N-4 for color negs without a lot of color crossover. Plus, there are no variable contrast color papers I am aware of to help deal with contrast at the printing stage. There are digital (gasp) possibilities but...

As for pegging shadows: we Zonies grew up on shadow-value placement; I feel fairly confident placing shadow values. However, when shooting roll film, I use a mid-tone as well for the most part. The only real danger when using an average value is in very contrasty situations, when the shadows can end up severely underexposed. Highlights will be hot as well, but that is not an issue with most black-and-white films; color is a different matter again. When shooting black-and-white with average readings in contrasty situations, I'll usually give an extra stop exposure to hold some shadow detail and then deal with the overexposed neg at the printing stage.

Best,

Doremus
 

markbarendt

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Thanks Doremus, very reasonable thoughts.

One thing that C-41 taught me about myself/my work, is that "normal" development works well for me.

I have brought that thought back to my B&W work and found it works just fine for me there too. My development target is to get the general "snappiness" I want, especially across the mid-tones. I find almost without exception that I prefer the result when I burn and dodge versus applying plus or minus development to a film, or a change of paper grade.

I give up fitting a scene to the paper in exchange for contrast consistency. Just a different priority.
 

jp498

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You guys are all wrong!
Average speed is Total distance divided by Total time.


I simply cannot resist. . .

And if direction is involved, it's velocity not speed as speed is a scalar quantity rather than a vector quantity.
 
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