simple question - focal lenghts

[Michael Fontana]

Just a simple question:

a doubled focal length will double the size of the objects in the image - correct?

Here's a testshot I did yesterday, with a 40 mm on a crop 1.3; but, as we know, for the object's size, crop or no crop doesn't matters. The main object is the white-lined roof...

As they are working at the tower, access is difficult; the shots have to be fine in the first session.

 

[Bart_van_der_Wolf]

Just a simple question:

a doubled focal length will double the size of the objects in the image - correct?

Yes, on a rectilinear projection the projected image scales linearly with focal length. Should the cranes/elevator(?) get in the way, multiple shots with non-overlapping crane structures will allow to remove the crane from a smartblended composite image (if need be with alpha masks to factor out the crane structures from the calculations).

Bart

 

[Jack_Flesher]

Depends on your definition of "double" the object size... It will double the AREA your original subject covers, but it won't increase it's width or height by double; it will increase width/height of your subject by root2...

 

[Doug Kerr]

Hi, Jack,

Depends on your definition of "double" the object size... It will double the AREA your original subject covers, but it won't increase it's width or height by double; it will increase width/height of your subject by root2...

No, if we are talking about an certain object at a (certain) substantial distance, doubling the focal length will double the width and height of the image of the object in the focal plane (a change in area of 4x, whatever that is good for).

 

[Jack_Flesher]

Of course it will Doug. My stupid and thanks for correcting me. I meant to clarify the opposite, that it takes a 1.4x increase in focal to double the size of the subject...

Stupid...

 

[Doug Kerr]

Hi, Jack,

Of course it will Doug. My stupid and thanks for correcting me. I meant to clarify the opposite, that it takes a 1.4x increase in focal to double the size of the subject...

Well, to double its area!

Best regards,

Doug

 

[Michael Fontana]

Thanks for making sure; I'll just get 1 - 2 minutes to get the shots done; so its crucial to know ahead exactly the image will look like.

Bart, these are elevators; to bring up reconstruction material to the tower. Off course, I want to avoid' em by going about 15 m more to the right, if I convince my top dog to talk to the other top dog ;-)

Same story will happen in 2010 again, the reconstruction of the tower takes about 5 years...

but it's the only solution, apart from taking a chopper, which I'm considering as well. The chopper though will not be allowed to be lower than twice the testshots heights: 70 m chopper versa 35 m tower...
so with the chopper, there will be a different perspective as well.

 

[Bart_van_der_Wolf]

Thanks for making sure; I'll just get 1 - 2 minutes to get the shots done; so its crucial to know ahead exactly the image will look like.

You're right, proper planning gets half of the job done ..., the other half is just coping with the unforeseen

. No, joking aside, one really needs to plan for eventualities (the fewer the better). The actual shoot can offer enough distraction as to jeopardise a successful result, although experience helps to increase the success rate.

Bart, these are elevators; to bring up reconstruction material to the tower. Off course, I want to avoid' em by going about 15 m more to the right, if I convince my top dog to talk to the other top dog ;-)

Yep, one needs to get the people in charge involved in one's endeavor, as if they can benefit from the cooperation. It often requires little more than some personal interaction skills, and a sincere "Thanks for you cooperation". That too is part of getting the job done. Usually people are quite willing to help.

Bart

 

[Deleted member 55]

Greetings Michael,

Would it not be better to shoot from one of the elevators stopped at the right floor?

 

[Michael Fontana]

Will

that elevator is not build for humans, but for materials only: I doubt that they will let me use it.

Yep Bart, cooperation is one key word, I've been working already two days, to scout for the best cam position, establish relations....

So here's a handheld stitch, showing the building of interest with the painting on its facade:

I don't like that viewing angle to much, as the court in the foreground challenges the building of interest; but its the only possible one in the court.
The white tent - at the left of the painting - is from the archeological institute, they found some roman's foundations - and will dig as long as they can.


The stitch was shot on top of the roof, at the left:

Theoretically, it would be possible to go up to the small windows of the grey facade, but they' re very small, no chance to bring a panohead in position.

The problem of the chopper is, that when flying low, flowerpots, etc of the surrounding old houses will fall ob the street; and be a danger for the people.

I spoke to the guys from the the archeological institute, they would probably even participate at the choppers cost, in exchange to some aerial shots.

BTW: the new roof will have about that shape: