Just a quicky

[graciousness]

Originally Posted by ccting

I thought sharpness is everything... Why we are not referring to the MTF curve from widest to smallest aperture. Difference lenses have different sweet points. Wider aperture at far distance should give sufficient DOF to the parade?

"Aim.. set, and SHOOT!"

It's not about sweet spots in this case as the OP has priority to get several subjects in focus at a given distance. If you go wider, less than f/4 per se, you narrow your DOF and risking getting blur on subjects that the OP wants in focus. Remember that there are several people in the shot here, not just one.

I don't like to complicate information with so much numbers as you do as it just doesn't help. You want to simplify, not complicate.

You need to learn to unclutter your head from all those numbers and simplify settings especially in scenarios where you don't have time to calculate and set up shots. You just have to do it quickly and shoot.

Sharpness is not jsut about what number you use on your aperture, but how you take the shot - least camera shake to no camera shake as possible, using fast enough shutter to freeze moving targets, etc.

Oh and if you really want to learn about sharpness and light - go shoot and put all those reading into practice instead of just visualising and conceptualising what you think you know.

Use your camera.

[RichardTaylor]

@ Graemey

This multi part DPS tutorial may help.

Exposure (1) A balancing act

The zone of sharpness (DOF) depends on.
(1) The distance to the subject.
(2) The aperture used
(3) The focal length of the lens.

This DOF calculator may help give you an idea.
Online Depth of Field Calculator

If I was shooting that scene I would either
(1) Shoot with a fairly small aperture (f16?) if you want a fair amount of the image in focus.
(2) Or shoot at a relatively wide aperture to isolate the subject.

Here are two examples from a parade I was shooting from the same spot..
#1

Camera Canon EOS 5D
Exposure 0.003 sec (1/400)
Aperture f/16.0
Focal Length 58 mm
ISO Speed 400
Exposure Bias -2/3 EV

#2 To isolate the subject.

Camera Canon EOS 40D
Exposure 1/2500 sec
Aperture f/4.5
Focal Length 140 mm
ISO Speed 200
Exposure Bias -2/3 EV

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@ ccting
What is sharp is important, however, not always is sharpness the most important thing and in some cases super sharp is the last thing you want for parts of some subjects
It depends on what you are trying to achieve.

Until you get the basics, including focus & exposure, right there is no point in thinking about sweet spots & MTF etc. Even then ask your self what is more imortant - shooting at the sweet spot or shooting for an optimised exposure where DOF meets your needs, shutter speed meets your needs and you are shooting at a relatively low ISO.
Sure I can shoot a lot of pics at a couple of stops down from wide open (sweet spot?), however it may mean I do not get a usable image

#3
Here is an example shot hand held in very low light.

Camera Canon EOS 40D
Exposure 0.006 sec (1/160) If I was shooting at a sweet spot (f8-f11I and 1/80 or 1/40 second) I think subject motion or camera motion would have been a major problem.
Aperture f/5.6 (wide open)
Focal Length 400 mm
ISO Speed 3200