Advice re: lens and perspective for 8x10

[aopie]

I posted a couple of weeks ago about finding the right 8x10 lens for a tight studio setting and got a lot of great advice, now I find myself with a perspective problem.

I'm shooting 8x10 vertically oriented full standing portraits (with my 250 mm Fujinon W lens) and I'm getting too much floor in the shot. I am constrained by needing the subject to be a certain size and position - I can't move them closer to the backdrop which I believe would help. To give you an idea how much floor I am seeing the floor is taking up 25% of the final image (height). In a vintage portrait I want to emulate the floor takes up 15% of the total image height, that 10% is the difference between elegance and clunkiness to my eye. Moving the camera up and down and changing the angle that way doesn't seem to help.

My understanding is that the only way to change the perspective on the floor in relation to the subject is to use a longer focal length lens, right? If I get the camera further back I will see less floor in relation to the subject at the same size.

The specifics of my setup: I'm currently shooting with the camera 10' from the subject. I have space to move it to ideally 13' (to 16' max) from the subject. My subject is 5' 6" on average, standing about 2' in front of a 8' high backdrop with 8' usable width.

If my use of lens calculators is correct I need between a 370mm and a 500mm lens but I don't know enough about lenses to be sure that I would have the right angle of view.

Any thoughts and suggestions? And, as I am not well educated about lenses, any suggestions of books to help me with that would be appreciated.

Thanks!

[Bob Salomon]

Changing the focal length does not do anything to perspective. If you want to change perspective you need to change the camera position.

However, in your case, assuming that your camera has front and/or back movements, all you need do is a lens rise or a back drop or a little of each.
Otherwise you can tilt your camera up and tilt your lens and back till they are level again. That is called indirect displacements. If you raise or lower your back you are doing direct displacements, The end result with each is the same.

You do realize that if you stay in the same camera position and use the same lens and reduce the foreground you will add the same amount of space above the subject, don't you?

If you don't want that then you have to use a longer lens or shoot closer.

[William Whitaker]

Perspective is controlled by the relationship of the camera to the subject, not by lens choice. You write of increasing the camera-to-subject distance, but that is only going to increase the amount of floor seen by the camera. It sounds as if you need to move the camera closer to the subject. But your question isn't really clear.

Edit: Bob was quicker off the mark than I...

[Old-N-Feeble]

The others are spot on and if you feel the need to crop then acquire a slightly longer lens. Regarding rise/fall of the front/rear standard: You can also just raise the entire camera... and this may be more appropriate because... a general rule-of-thumb for full-length portraits is to set the camera at chest height.

[aopie]

Hm. Thanks for this. So, I'm really not understanding how the lens works. I tried raising the camera but will have to try again and see if I can get it. I also tried some camera movements but not in a very systematic way. I need to shoot with the lens open so raising the front standard - which I have done in the past - poses a problem since I start to see fall-off.

[Old-N-Feeble]

PERSPECTIVE... is set by camera distance, height and angle.

IN-CAMERA CROPPING... is set by lens focal length.

FILM SIZE... Does Not Matter

[Colin Graham]

Just to be clear, aopie is talking about off-axis perspective. The shorter the lens and the closer to the subject, the steeper the angle is to the extremes of the composition. As a result, the greater the apparent distance is off-axis between the subject and the background.

[Tracy Storer]

Why not try working it out via magnification ratios? Your subject is 5'6"(66") How tall do you want them to be on the film?
Start there. You say you want the floor to be 15% of image height (15% of 10 is 1.5" = OK) How much head room do you want? That leaves subject height on the film. Figure out what that is in relation to ACTUAL height (66") and you can have the mag ratio. With that, you can easily work out needed bellows extension and lens to subject distances for any given focal length.

As usual, we've got people trying to be helpful, without having the complete picture. Help us help you.

[aopie]

Thanks Tracy and All,

Always hard to give a complete picture of the specifics, mostly because of my limited knowledge. I'm trying to upload a couple of pictures to give a visual aid but can't get it to upload.

Target:
I want 1.25" headroom, and .75" foot room (from front of feet to bottom of picture). I want the apparent floor (from the area at the bottom of the picture showing floor in front of subject's feet back to where the wall and floor meet) to take up the lower 1.5" (to 1.75" max). The feet come down into the apparent floor area. So, in this scenario the subject is 8" tall. I don't know how to do the math involved in going from there.

That information help or hinder? I wish I could get the images to upload, doesn't seem to work with an Ipad.

[Tracy Storer]

OK, magnification is 0.12. With your 250mm lens, you should get the right scale with your lens 91.86" away from your subject. Bellows should be just over 11"
If your camera and lens are too low, you will see the top of your 8' high background, but based on your data, it is unlikely you will want to have the camera that low.
The same magnification with a 300 lens will have the back of your camera just about 10.5' from your subject.
The same magnification with a 360 lens will have the back of your camera just over 12' from your subject.