Field of View information required

[JTPhotographics]

Hi gang,

Yesterday I took position of a new motorised panoramic head. The head allows for the digital input of information to allow the head to calculate the frames etc required for the desired pano. One of the questions it asks is the FOV for both Horizontal and Vertical.

My go to lens for shooting Panos is a Sigma 50mm F1.4 EX DG HSM. When I look at the tech specs is says Angle of View 46.8 degrees. I believe this is measured across the diagonal and Im wondering if this can be translated to Horizontal and Vertical degrees?

Any help is greatly appreciated.

For information, this is on a Pentax K5 if that makes any difference.

Regards
John

[ricktas]

field of view has two dimensions to it, width and height, generally the one stated in the technical information is the horizontal field of view. So your lens has a field of view of 48 degrees, to get a pano that goes all the way round you, you need 360 degree, but for stitching each image to the next it is worthwhile having a good level of overlap.

[JTPhotographics]

Thanks Ricktas,

I have shot panos before using a manual head and all went well with the overlaps etc. With this new one the onboard computer is asking for H & V FOV. On the Sigma site it only lists the Angle of View (in Diagonal). Im wondering if this can be converted etc.

[Cage]

A bit of bush maths may help.

Your K5 sensor is 4928 x 3264 pixies, vertical plane being 66.233% of the horizontal. So 46.8° x 66.233% = 30.1°, probably within a poofteenth of spot on.

[nardes]

Here’s some I have used although the list of cameras may not be up to date:

http://www.howardedin.com/articles/fov.html

http://www.mat.uc.pt/~rps/photos/angles.html

http://www.tawbaware.com/maxlyons/calc.htm

Cheers

Dennis

[JTPhotographics]

Thanks Cage

Im still trying to work out the maths you used for this one :)

If the Horizontal is 30.1% whats the vertical?

(Why do I feel Im about to be shown how dumb my question is)

John

[Morgo]

http://focusphotographers.org/shooting-multi-row-panoramas/

- - - Updated - - -

Scroll down a bit

[arthurking83]

This is a hard one to figure out(depending on how accurate you want to be!)

One problem is that lenses are always the focal length they're pretending to be(and they can also change focal length within themselves depending on their design and focus abilities!)

But if you want super accurate values, then you'd need to physically test the lens yourself.

If you read the TDP(digital picture) review of the Sigma, it's noted that the angle of view of the Sigma is a little wider than the 50mm Canon lens:


Focal lengths are supposed to be rated at an infinity focus distance, but even at hundreds of feet, the Sigma still frames the scene a similar percentage wider than the Canon lenses. While this is a real difference, I'm not sure it matters if your prime lens frames like 50mm or 46.5mm. It's a small difference.

So the question is, is the Canon lens more than 50mm(more likely to be something like 51mm) or is the Sigma lens more like 46mm like TDP seems to think
Either way, it's said to be 93% wider in terms of FOV.

So to use a standard focal length to FOV calculator will produce a margin of error .. because the focal length of the lens may not be what it seems.
(note that manufacturers are allowed this leeway too!)

There is a calculation tool available on the net, that specifically gives FOV values for certain LENSES(ie. not generic focal lengths!).
Problem is that it doesn't appear to have been updated for a while, and we don't know if the calculations are real/physical/tested .. or hypothesised, working from hypothetical values stated here there and everywhere else! :confused:

Here's the link to that if you're curious: (http://www.sweeting.org/mark/lenses/sigma.php)

Going by the cameras listed as examples, it looks like the calculator hasn't been updated since about 2005-6!

the Sigma value of 46.8° FOV seems to be for a 24x36 mm frame too .. so take into account your cropped sensor FOV relative to that.

If we can assume that you don't mind a 10% error margin to work with, using that Lens FOV calculator, and using the Sigma 50/2.8 macro as a guide and a Nikon APS-C as the sensor:

You'll get FOV values of 26.9° on the Horizontal and 17.44° on the Vertical .. and 31.4 on the Diagonal.
If we use a 10% margin or error make that 24.2-29.6° Horizontal, and 15.7-19.1° Vertical

If you don't mind a bit of inaccuracy .. I'd say 25° V and 17° H

hope that helps

[Cage]

Crop factor. :Doh:

[JTPhotographics]

Dont beat yourself up Cage, you were only 5 degrees off..

I have to say, this thread is immensely interesting to me. I really appreciate all of the help given.

As a side note, I have emailed Sigma with this exact question. If they reply with the information I am looking for, I will post it as it will be fun to see who got closest.

John

[JTPhotographics]

Good news folks. I have it worked out I think. Using the FOV of 25 and 17 seems to work (just have to remember to flip them as I am shooting in portrait mode). I have also finally figured out the motorised head and plan on giving a few test runs tonight. I will post back the results.

Cheers
John

[arthurking83]

I think it's always best to give yourself a bit of wiggle room with panos and stitching.

So the actual FOV horizontally is 26point something degrees, then the value of 25 gives you enough space for any anomalies at the periphery and some room to stitch more accurately.

I'm assuming that the pano head thing you have comes with auto stitching software too?

[JTPhotographics]

HOwdy.

The Pano head is actually a telescope head that also has functions for multi-row panos.. I will be using PTGui for the stitching

[JTPhotographics]

If you would like to see the results, I have posted them here:

http://www.ausphotography.net.au/forum/showthread.php?144296-New-motorised-pano-head-results&p=1336492#post1336492

Thank you all for your help. Im a happy man.

John