Bjorn Reviews the Nikon D700
Bjørn Rørslett (Norway) is very interesting- everytime I read something from him, there’ll be something in there that makes me think either, “He’s bullshitting” or “I’m not certain what he’s talking about”. I always believe it’s the latter, but it always strikes me as the former.
So for example, this time he’s found out that the way they’re measuring the viewfinder coverage really equates to 90% coverage, not 95% (bolding is mine, making text red is his):
…here is the definite answer to the question of viewfinder coverage: the 95% figure is NOT a planar measure as it should be, but linear. Hence actual frame coverage is 90%. This figure will vary slightly with the actual lens used. I tested with the 45/2.8 PC-E. Traditionally, frame coverage is specified for a 50 mm lens at infinity.
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A new confirmation: The dust reduction assemblage adds a frame structure inside the mirror box, just in front of the shutter curtain. This might be a stop for the shaking system? Whatever the explanation, it is clear that this frame will mask the finder slightly. This lends support to the explanation I got from Nikon techs earlier that the dust-removal system was responsible for the slight reduction in finder coverage on the D700, NOT the built-in flash since the prism heads appears to be large enough on its own.
I really have no idea what the difference between planar and linear is in this context, but I’ll accept his word for it.
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July 18th, 2008 at 4:04 am
I don’t really understand the importance of this frame coverage question.
As I understand it you will get more in the picture than you see in the viewfinder. Is that right?
Isn’t that a good thing? You can always crop afterwards if you want.
July 18th, 2008 at 6:49 am
He’s talking about the difference between 95% coverage in one direction across the frame, (eg. if the image was 95mm wide, and the frame was 100mm) and 95% of the area of the frame, eg. if the image was 97.5mm by 97.5mm the area would be 9506mm^2, instead of 10,000mm^2 for 100×100mm.
Area v’s length in other words.
July 18th, 2008 at 11:18 am
If there is 95% coverage in each direction, he would be correct from the perspective of area.
Here’s how to calculate it:
The Nikon FX frame is 36mm x 23.9mm resulting in a total area of 860.4 sq mm
95% of 36mm is 34.2mm.
95% of 23.9mm is 22.705mm. 34.2mm x 22.705mm = 776.511 sq mm
776.511 sq mm / 860.4 sq mm = 90.25%.
But to me, unless you’re using a tripod and shooting grids, it is absolutely impossible to frame that accurately anyway. In the horizontal dimension, you’re talking .9mm on each side. NO ONE can frame that accurately. Camera shake alone can account for .9mm In the vertical direction, you’re talking about less than .6mm on each side. That’s about the thickness of a fingernail.
July 20th, 2008 at 5:30 pm
I don’t consider it important to most people but it’s a problem because what you see isn’t what you get. Some photographers or jobs (wedding, event, journalism?) may not do any post and the extra image outside your view might not be pleasing.
What bothers me most is the size of the image in the viewfinder, the finder magnication. Either I’m getting older or it’s getting smaller.