In which I attempt to calculate the perfect lens for shooting rock shows.
[edit: in which i completely miscalculate any number of figures. Math is hard, let's go shopping.]
Supposing (and this is extravagantly generous) the average lighting condition is such that ISO3200, f/1.8, and 1/400sec works out to a correct exposure ... I should say that I'm taking those values from one of my favorite shots (of Shawn Kyle of the Beauvilles) from the Sleepy Vikings/The Beauvilles/Dead Confederate/Deer Tick show at Crowbar.
But ISO 3200 is too noisy on the 30D, and I'd really rather keep it to no higher than ISO 800, which is two stops. To compensate, shutter speed has to drop to 1/100sec. That's OK, even without IS, for focal lengths up to about 85mm, and with stop motion pretty well if it's not *too* fast.
But! Not every lens goes f/1.8. Suppose we're looking at f/2.8? That another one and one third stops ... to compensate, we'd have drop our shutter speed to 1/40sec. Ouch. Handheld without IS only to about 25mm. But guess what? I have an IS lens that lines up nicely there, so I don't have to worry too too much about camera shake. But 1/40 doesn't freeze motion as much as I might like ... will work in a pinch, but not if the act is particularly frenetic.
So, that's all good to know, but what about focal length? Well, focal length effects to main factors, field of view & (with aperture) depth of field. DOF is the easy one ... I figure I want a minimum of a 9" and no more than maybe 3 feet. A foot might be ideal. In any case, I want enough that if I blow focus the shot can be saved, but not so much that backgrounds are in focus.
FOV is harder for me ... mostly because I'm not really sure what fields I need. I guess a 3' x 2' portrait for a one-shot and ... uhm ... maybe 7' x 10.5' landscape for two or three performers, from head to toe?
So, focal lengths/apertures(shutter) @ focal distances yield DOF, FOV
17/2.8(1/40) @ 10' 16.5' 13.24' x 8.82'
17/2.8(1/40) @ 15' 89.9' 19.85' x 13.24'
17/2.8(1/40) @ 17.7' Infinite 23.43' x 15.62'
20/2.8(1/40) @ 10' 9.75' 11.25' x 7.5'
20/2.8(1/40) @ 15' 29.3' 16.88' x 11.25'
20/2.8(1/40) @ 20' 97.9' 22.5' x 15
28/2.8(1/40) @ 10' 4.33' 8.04' x 5.36'
28/2.8(1/40) @ 15' 10.3' 12.05' x 8.04'
28/2.8(1/40) @ 20' 20.1' 16.07' x 10.71'
35/2.8(1/40) @ 10' 2.69' 6.43' x 4.29'
35/2.8(1/40) @ 15' 6.22' 9.64' x 6.43'
35/2.8(1/40) @ 20' 11.4' 12.86' x 8.57'
50/1.6(1/125) @ 10' 8.64" 4.5' x 3'
50/1.4(1/160) @ 15' 1.46' 6.75' x 4.5'
50/1.4(1/160) @ 20' 2.61' 9' x 6'
50/1.8(1/100) @ 10' 9.72" 4.5' x 3'
50/1.8(1/100) @ 15' 1.84' 6.75' x 4.5'
50/1.8(1/100) @ 20' 3.3' 9' x 6'
50/2.8(1/40) @ 10' 1.29' 4.5' x 3'
50/2.8(1/40) @ 15' 2.94' 6.75' x 4.5'
50/2.8(1/40) @ 20' 5.29' 9' x 6'
55/2.8(1/40) @ 10' 1.07' 4.09' x 2.73'
55/2.8(1/40) @ 15' 2.42' 6.14' x 4.09'
55/2.8(1/40) @ 20' 4.34' 8.18' x 5.45'
85/2.8(1/40) @ 10' 5.28" 1.51' x 1.01'
85/2.0(1/80) @ 15' 8.52" 2.27' x 1.51'
85/1.8(1/100) @ 20' 1.13' 3.03' x 2.02'
Gah, I gotta post this so I don't lose it whenever. I'll try to remember to edit it up ...
Supposing (and this is extravagantly generous) the average lighting condition is such that ISO3200, f/1.8, and 1/400sec works out to a correct exposure ... I should say that I'm taking those values from one of my favorite shots (of Shawn Kyle of the Beauvilles) from the Sleepy Vikings/The Beauvilles/Dead Confederate/Deer Tick show at Crowbar.
But ISO 3200 is too noisy on the 30D, and I'd really rather keep it to no higher than ISO 800, which is two stops. To compensate, shutter speed has to drop to 1/100sec. That's OK, even without IS, for focal lengths up to about 85mm, and with stop motion pretty well if it's not *too* fast.
But! Not every lens goes f/1.8. Suppose we're looking at f/2.8? That another one and one third stops ... to compensate, we'd have drop our shutter speed to 1/40sec. Ouch. Handheld without IS only to about 25mm. But guess what? I have an IS lens that lines up nicely there, so I don't have to worry too too much about camera shake. But 1/40 doesn't freeze motion as much as I might like ... will work in a pinch, but not if the act is particularly frenetic.
So, that's all good to know, but what about focal length? Well, focal length effects to main factors, field of view & (with aperture) depth of field. DOF is the easy one ... I figure I want a minimum of a 9" and no more than maybe 3 feet. A foot might be ideal. In any case, I want enough that if I blow focus the shot can be saved, but not so much that backgrounds are in focus.
FOV is harder for me ... mostly because I'm not really sure what fields I need. I guess a 3' x 2' portrait for a one-shot and ... uhm ... maybe 7' x 10.5' landscape for two or three performers, from head to toe?
So, focal lengths/apertures(shutter) @ focal distances yield DOF, FOV
17/2.8(1/40) @ 10' 16.5' 13.24' x 8.82'
17/2.8(1/40) @ 15' 89.9' 19.85' x 13.24'
17/2.8(1/40) @ 17.7' Infinite 23.43' x 15.62'
20/2.8(1/40) @ 10' 9.75' 11.25' x 7.5'
20/2.8(1/40) @ 15' 29.3' 16.88' x 11.25'
20/2.8(1/40) @ 20' 97.9' 22.5' x 15
28/2.8(1/40) @ 10' 4.33' 8.04' x 5.36'
28/2.8(1/40) @ 15' 10.3' 12.05' x 8.04'
28/2.8(1/40) @ 20' 20.1' 16.07' x 10.71'
35/2.8(1/40) @ 10' 2.69' 6.43' x 4.29'
35/2.8(1/40) @ 15' 6.22' 9.64' x 6.43'
35/2.8(1/40) @ 20' 11.4' 12.86' x 8.57'
50/1.6(1/125) @ 10' 8.64" 4.5' x 3'
50/1.4(1/160) @ 15' 1.46' 6.75' x 4.5'
50/1.4(1/160) @ 20' 2.61' 9' x 6'
50/1.8(1/100) @ 10' 9.72" 4.5' x 3'
50/1.8(1/100) @ 15' 1.84' 6.75' x 4.5'
50/1.8(1/100) @ 20' 3.3' 9' x 6'
50/2.8(1/40) @ 10' 1.29' 4.5' x 3'
50/2.8(1/40) @ 15' 2.94' 6.75' x 4.5'
50/2.8(1/40) @ 20' 5.29' 9' x 6'
55/2.8(1/40) @ 10' 1.07' 4.09' x 2.73'
55/2.8(1/40) @ 15' 2.42' 6.14' x 4.09'
55/2.8(1/40) @ 20' 4.34' 8.18' x 5.45'
85/2.8(1/40) @ 10' 5.28" 1.51' x 1.01'
85/2.0(1/80) @ 15' 8.52" 2.27' x 1.51'
85/1.8(1/100) @ 20' 1.13' 3.03' x 2.02'
Gah, I gotta post this so I don't lose it whenever. I'll try to remember to edit it up ...