camera footprint

[endeavour]

hi everybody

i have a question: i tried to calculate the footprint (area covered) of a camera setting with my canon 5dsr having 8688x5792 pixels on a 36x24mm sensor which is a SPS of 0.00414365mm. now with a 35mm lens and 500mm distance i calculate a covered area of 514x342mm. ((calculation according to the "US Bureau of Land Management Publication: Tech Note 248 on Photogrammetry"))

 

BUT

if i look thru the camera viewfinder the covered area at 500mm distance the covered area is only approx 410x273mm 

to achive an area as the calculated 514x342mm i must set the lens on 610mm 

 

any ideas whats wrong here? it's still an about 20% difference from calculation to "reality"

 

thanks everybody for every sugestion

best greetings from zurich switzerland

martin

[macsurveyr]

Hmmm,

 

Not sure I can explain it since the calculated footprint can be confirmed. That leaves what you are seeing to be the mystery. I believe spec wise, the Canon viewfinder is supposed to cover ~96% of the actual footprint so again, not sure I can explain it based on the numbers.

 

Tom

[endeavour]

thank you Tom

i'm talking of course not about the viewfinder but about the covered area in an image which i measured now again along with other prime lenses and a mirorless lumix GF1. see the results attached chart. with the canon lenses the difference between calculation and real world is irregular while with lumix zoom lens more regular but not really regular either. the difference is allways in the 20% range which is quiet a bit.

 

still looking for an explanation. or a formula . 

 

thanks everybody

Martin

 

 

 

[macsurveyr]

Martin,

 

There is a more exact formula that can be used to calculate the footprint at closer distances such as you are doing but it is still an approximation. You can explore this website for more information. Depth of Field (DoF), Angle of View, and Equivalent Lens Calculator

 

Make sure to click on the See Notes link under the 2 methods for calculating the field of view. Once there, be sure to follow the other link Calculation the Angle of View: When Theory Meets Practice.

 

Additionally, lens distortion can account for a few percent less (usually) field of view.

 

Tom

[endeavour]

thank you Tom

great site! i'll check it out and will give feedback.

[endeavour]

hi Tom. 

now i have read the website. and now i understand how it works and why i had this differences. so far i hav'nt tried the formula but sure i'll have better results. thank you again so much.

 

sunny greetings from zurich switzerland