App ?

[Domip]

Hi to all,
Does someone knows if an app exists, or a formula that can tell wich lens you must/can use, when only a certain surface (3x3meters) at an certain distance (2,8meters) is known? Sometimes a client asks me if I can photograph a painting in a constrained space, like the example given...

[Alex]

For a useful app:

https://pcamapp.com/Pro/pCAM_FILM_+_DIGITAL_PRO.html

Module: Field of View

It doesn't take into account magnification factor so for I'd give yourself 5% leeway <5metres & 10% <3m. AFAIK there isn't a calculation for working distances <4xfocal length.

Alex

[jerome_m]

I would use the intercept theorem https://en.wikipedia.org/wiki/Intercept_theorem.

If L is the size of the painting, l, the size of the sensor, D, the distance to the painting and f the focal length, you would have f=l*D/L.

In the given case: L=3000mm, l= 51mm (H4D-50), D= 2800mm and f= 51*2800/3000=47mm. The 50mm lens is a bit long, you will need the 35mm.

[ChrisL]

Gracious me, it does a lot and so it should for £28.99.

Distance = Subject Height x focal length / Image height (with all units same)

Image height is the height of your sensor or the size you want the image to be on your sensor.
(Below 10x focal length this changes but sounds like we are not going macro here)

Take an analog example: Hasselblad 500c/m 80mm lens on 6x6cm A12 back with your 3m high subject all in cm so:  8x300/6 = 4 meters required, swop to 120 macro for quality 12x300/6 = 6 meters now needed. No room?  use the 50mm, needs 2.5 meters, an App sounds overkill to me.

Yes I know the A12 image is around 5.6cm not 6cm but if you want to work to decimal places please do and remember this is to image plane so your camera needs to fit in, don't measure film plane to the wall.


Just beaten by Jerome, rather than change lens get a bigger sensor :-)

[Domip]

Thanks guys for this info...!
I'll use the formula like Jerome explained, and adapt to 32,9mm back of my H5D-50c MS.

[Alex]

Gracious me, it does a lot and so it should for £28.

Ouch - £28!! I remember buying it for only £10 - and only then because of being an "at hand" phone solution.

Alex