NeilF92
Crewdog
Registered: 11/20/06
Posts: 1,712
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Reply with quote | #31 |
To be honest Pete I had not got to that stage yet - I never really used APM to create a painting before ( apart from the Buccaneers for which I just used whatever came out of APM at what I figured was a reasonable viewing distance.).
Embarking on a serious painting this time and knowing I'd have to get it right I was working my way through Joes manual again.
I had deduced that I would need to relate image size to canvas but not got round to the detail of doing so. My initial post here was just a crude colour / general layout for discussion with my friend .
Shortening the viewing distance certainly alters the image - particularly the far wing - but having done so the image still does not match to Kevs because I think we are using quite different parameters .
This image is calculated at what I estimate to be 145 ft viewing distance. If I've got the geometry right this one should relate the a/c image to a 24" canvas but I'm still studying this bit of the exercise.
Thanks all for your inputs - I guess my learning curve on APM has been boosted slightly prematurely but all to the good.
Attached Images:
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NeilF92
Crewdog
Registered: 11/20/06
Posts: 1,712
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Reply with quote | #32 |
Just like to add my thanks to Kev and Gray for their patience in working through this with me . I guess I was right - but for all the wrong reasons.
You folks were right for all the right reasons.
And thanks to Pete for getting to the nub of the issue so quickly.
Never having done the scale COV to canvas window exercise with APM I had no idea the extent to which this would dictate the viewing distance . I am surprised at how short it has come down to -145ft ,just a quarter of my original View Distance choice of 600 ft - always assuming my geometry/arith is correct.
Thanks again - good to have friends who take time to help.
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PeteWenman
Moderator
Registered: 10/29/06
Posts: 899
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Reply with quote | #33 |
Neil hi
Just to add to the cone of vision bit, this is what I have picked up over the last couple of years. Like you my first APM plots were based on a random distance with no thought to the size of the canvas. (It's a good thing the eye will correct a lot of perspective issues  ).
Wade Myers in his DG manual makes mention of the physical view distance of a painting being 125-140% of the paintings greatest dimension. So a 24" canvas should be viewed from 30" to 33.6". This is one way of establishing the cone of vision (or angle of vision) which at 125% view distance is 44 degrees, or at 140% view distance 39 degrees.
Joe Demarco suggests that images at, or within 30 degree COV are within the comfort range of human vision, but perspective starts to be exaggerated when the COV is much wider than 40 degrees.
If interested drop me your email address and I'll copy you an article that Joe put together last year covering this. It makes it a lot easier to understand, and deals with the sizing of the aircraft on a canvas far more easily than I could otherwise explain here.
By my calculations based on the 145' view distance, and 30 degree COV and a 24" canvas the Blenheim should be just under 14" wide. (13.89" to be precise). You can scale the APM data to this and draw it, or as you did already print the preview cartoon and enlarge it to match.
HTH
P
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NeilF92
Crewdog
Registered: 11/20/06
Posts: 1,712
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Reply with quote | #34 |
Pete
Thanks for that - yes I make the Blenheim around 13.5 using the size factor calculation Joe advocates , that gave me 5.49.
I think I know the article you refer to - I was reading it just a few days ago - I had managed to figure out the size/ scaling factor - I just need time now to assimilate it all and put into practice .
The view distance/ canvas size tie in is good though.
I understand better what Joe is saying now - prior to this I'd been more concerned with what represented a normal viewing distance in the low level photog. game , usually working from own photos for paintings - much happier now I understand image size/canvas/ view distance.
regards
Neil
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joedemarco
Moderator
Registered: 11/21/06
Posts: 131
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Reply with quote | #35 |
Hi Neil, FYI, viewing distance sometimes does funny things to perspective. A banked Spitfire is notorious for giving the impression that the far wing is longer than the near one. It's due to the dihedral and the fact that the far wing projects more of its lengh on the flat picture plane than the near one which is at a lesser angle to the line of sight. The impression is heightened as the viewing distance (camera lens to object) is increased. A similar thing happens in pictures of the Blenheim. Kevion was right when he brought up the probability that the viewing distance (600 ft. wasn't it?) to your airplane was too great for its size and placement, its "nearness" to the viewer, in your composition. Ordinarily I'd take umbrtage to his faulting APM, but under the circumstances that came to light in this thread, all is forgiven.  A couple of years ago a bunch of us had a go-round over the same matter of the Blenheim's wings and I made the attached set of APM comparisons. In each image the azimuth and elevation angles are the same, but the viewing distances are changed. One can see the differences in the apparent length of the near and far wing panels. The last one, at 400000 ft.—yes, 75 miles —for all practical purposes that's infinity—is about as bad as it will ever get. Kevion, you gotta have faith; APM is a mathematical camera. I heartily endorse all the good things Neil said about it. |
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NeilF92
Crewdog
Registered: 11/20/06
Posts: 1,712
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Reply with quote | #36 |
Thanks Joe - Kev , Gray and Pete - I wish I'd got to the bit of the manual dealing with all this before I posted the damn colour study - but it's all ended happily  .
Don
Would this thread be more appropriate moved to the APM section? So the lesson isn't lost for others who may follow ?
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joedemarco
Moderator
Registered: 11/21/06
Posts: 131
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Reply with quote | #37 |
Good idea to move it to the APM section. Would appreciate if someone can tell me how to do that. I'm pretty good at perspective but pretty dumb when it comes to maneuvering in Cat 2.
Would appreciate if anyone cares to take me on in Posting to Cat 2 -101.
Joe
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