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Pawlowski6132
27-Jul-2017, 18:59
So, I'm sure there is a formula or online calculator or spreadsheet somewhere to help calculate the answer to this but, here's what I'd like know:

On a 8x10 camera, using a 450mm lens, with a person standing 15 feet away from the lens, what is the required bellows extension to get a head-and-shoulders shot?

Can someone point me to some resources I can study?

thanx much

jrp

stawastawa
27-Jul-2017, 22:46
try playing with this simulator,
though I think you will have better luck playing and measuring the bellows extension yourself.

my quick test shows that a 450mm lens will be close to torso / full body than a head and shoulder image at 15ft subject distance.
http://apenasimagens.com/en/focal-length-distances-and-framing/?preview=true

Emmanuel BIGLER
27-Jul-2017, 23:40
Hi!

The key factor to properly answer your question is the magnification ratio.
For a head & shoulder portrait on a 8"x10" format, you'll need something 2x or 3x bigger as a frame on the subject.
This implies a magnification ratio M = (image size) / (object size) between 1:2 = 0.5 and 1:3 = 0.33

Hence the different working distances are given as follows:

Distance from the subject to the lens = f(1+1/M) = between 450 mm x (1+2) and 450 mm x (1+3) = between 1350 mm and 1800 mm

Total bellows draw (for a non-telephoto, quasi-symmetrical lens) = f(1+M) = between 450 mm x (1+0.5) and 450 mm x (1+0.33) = between 675 mm and 600 mm

Additional bellows draw beyond the focal point (infinity-focus setting) = f M = between 450 x 0.5 and 450 x 0.33 = between 225 mm and 150 mm.
The formula f M giving the additional bellows draw beyond the focal point is valid for all kinds of lenses including telephoto lenses (and including retrofocus lenses, but no such lens exists, to the best of my knowledge, for the 8"x10" format).

Pawlowski6132
28-Jul-2017, 06:30
Both responses spot on what I was looking for.

thanx for taking the time.

I'm a little smarter...

jrp

Pawlowski6132
28-Jul-2017, 07:09
Oh, one more thing (and I should know this by now)...

With a 450M, lets say, when I am focused at infinity, the bellows extension is approximately 450mm correct? if so:

1. What does this mean, in practice, with regards to what will or will NOT be in focus??
2. The closed focus plane to the lens is the "minimum focus distance"?

thanx

Ken Lee
28-Jul-2017, 07:17

28-Jul-2017, 09:21
All the math in the field is pretty useless, because you are focused on the composition.

Use Quickdisk from a photographer in Austria and enjoy your life as a large format photographer. It is free of charge. You just need a decent printer, a cutter, scissors and 15 minutes.

Quickdisk (http://www.salzgeber.at/disc/)

Vaughn
28-Jul-2017, 09:48
Nicely done, Ken.

Personally, if I am worried about bellows extension w/ B&W film, I usually double the exposure -- same with reciprocity failure compensation. Close enough to get what I want.

Drew Bedo
29-Jul-2017, 08:05
I regularly work in 4x5. My most commonly used focal lengths are 90mm, 150mm and 210mm.

What I do::

I have pre-calculated the extra exposure for the two longer lenses. The 150 is a six inch lens. For each one inch of extension beyond infinity (6") I open up 1/3 stop.

The 210mm is close to (but not exactly) an eight inch lens. With this lens, I add 1/4 stop more exposure for each inch beyond infinity, which I approximate as 8".

I have used the 210mm on my 8x10 with small front5 movement and this method works fine.

Your 450mm is nearl y(but not exactly) a twelve inch lens (at 11.7"). Fot this lens, every two inches beyond infinity will need 1/3 stop extra exposure.

After focusing, I measure from the front of the lens board to the film plane and work it out. No formula or head math, and I can do it with a cold wet wind blowing in my face when I am tired.

You can work through the formula with an app on another piece of expensive gear, but this method has worked well for me hands-free.

Bill Burk
29-Jul-2017, 09:46
The Quickdisc look like a very easy and sound solution.

Pere Casals
29-Jul-2017, 10:05

This a very clear way to explain all that, thanks.

Leigh
29-Jul-2017, 13:39
Oh, one more thing (and I should know this by now)...
With a 450M, lets say, when I am focused at infinity, the bellows extension is approximately 450mm correct?That's only true of lenses with modest focal lengths, not true at either extreme.

The correct definition is:
The infinity-focus distance is from the film to the REAR NODE of the lens.

For lenses of modest focal length, the rear node is at or close to the lensboard.
For long lenses the rear node will be in front of the lensboard, sometimes by hundreds of mm.
For short lenses the rear node will be behind the rear lens element, perhaps by tens of mm.

I expect your 450mm lens falls into the telephoto design group, with the node out in front.
Of course, that depends on the specific make and model of lens you're using.

The distance commonly quoted is the Flange Focal Length of the lens.
That's the distance from the film to the lensboard when focused at infinity, i.e. the bellows draw.
You'll find that on every lens datasheet.
it may be substantially different from the lens' focal length

- Leigh

Dan Fromm
29-Jul-2017, 14:44
That's only true of lenses with modest focal lengths, not true at either extreme.

Leigh, you are considerably mistaken. That the nodes are near the diaphragm is true for lenses of normal (not telephoto, not retrofocus) construction. The 450/9 Nikkor M is a tessar type, not a telephoto. Per Nikon its flange-focal distance is 428.4 mm.

Bill Burk
29-Jul-2017, 15:25
The Quickdisc look like a very easy and sound solution.

For bellows extension exposure correction. Funny I can't see bellows and extension together in a sentence without thinking exposure correction. And that's not the question here.

Bill Burk
29-Jul-2017, 15:27
Leigh, you are considerably mistaken. That the nodes are near the diaphragm is true for lenses of normal (not telephoto, not retrofocus) construction. The 450/9 Nikkor M is a tessar type, not a telephoto. Per Nikon its flange-focal distance is 428.4 mm.
I've never known Leigh to be mistaken on matters related to optical design. Looks like he's covered the telephoto and retro- focus designs in his post. Where did you see a mistake?

Dan Fromm
29-Jul-2017, 15:41
Bill, since you asked, the line I quoted is simply wrong. Long focus lenses don't have to be telephoto and in fact few of the long focus lenses that LF photographers use are teles. There are very few retrofocus lenses for LF.

Bill Burk
29-Jul-2017, 16:18
Oh right, you mean your lens, and many/most LF lenses.

Some long LF lenses are telephoto of course, with the node out in front, like my Dallmeyer.

Dan Fromm
29-Jul-2017, 16:45
Bill, not my lens, the OP's. Or, more exactly, the 450/9 Nikkor M that the OP gave as an example. And the vast majority of lenses for LF.

Leigh over-generalized.

Bill Burk
29-Jul-2017, 18:18
I'll tell you one thing, the Internet looks weird on a phone. I'm still getting used to it. Makes it harder to read the whole discussion.

I'm no good as an optical designer, so I rely on friends.

I was surprised to find out my lens was telephoto when I tried to photograph the last solar eclipse. I built a film plane up based on the "focal length" of my lens and found I was off by a half inch because ... well the plane wasn't where I thought it would be ...

Leigh
29-Jul-2017, 19:37
Leigh, you are considerably mistaken. That the nodes are near the diaphragm is true for lenses of normal (not telephoto, not retrofocus) construction. The 450/9 Nikkor M is a tessar type, not a telephoto. Per Nikon its flange-focal distance is 428.4 mm.Sorry, Dan, but I am not mistaken.

My comments suffer from the same problem as all generalities.

The FFL for the Nikkor M 9/450 is 435.4mm.

The FFL for the Fujinon T 8/400 is 226.5mm, much shorter than the optical focal length.
The FFL for the Nikkor T 9/600 is 409.8mm, "
The FFL for the Fujinon T 12/600 is 383.9, "

As I said previously, it depends entirely on the lens design .
The OP said "a 450mm lens", not further identified.

- Leigh

Dan Fromm
30-Jul-2017, 06:14
Sorry, Dan, but I am not mistaken.

The OP said "a 450mm lens", not further identified.

- Leigh

Please see post #5 in this discussion.

Pawlowski6132
30-Jul-2017, 16:06

Honestly, this is everything I needed. Thanx. Very well written and organized.

Who could have written such great material????

Pere Casals
30-Jul-2017, 16:58
Sorry, Dan, but I am not mistaken.

My comments suffer from the same problem as all generalities.

The FFL for the Nikkor M 9/450 is 435.4mm.

The FFL for the Fujinon T 8/400 is 226.5mm, much shorter than the optical focal length.
The FFL for the Nikkor T 9/600 is 409.8mm, "
The FFL for the Fujinon T 12/600 is 383.9, "

As I said previously, it depends entirely on the lens design .
The OP said "a 450mm lens", not further identified.

- Leigh

The general case for LF lenses is that flange to film distance is very close to focal distance in the vast majority of the cases. Most popular lenses follow that, all Symmars, Sironars, Nikkor SW, W, M...

Main exception is telephoto designs that are suitable for field cameras with limited max bellows extension, at the cost of some handicaps like lower max aperture. A few extreme wide angles are retrofocus type, so also an exception.

Here http://www.largeformatphotography.info/forum/showthread.php?13697-aperture-position&p=111996&viewfull=1#post111996 there is an interesting notice about where pupils and nodal points are located.

For barrels, you have to take the barrel mid point, as the lens is placed in front of the plate, and then in most cases it will also match closely.

With convertible lenses it happens same effect than with barrels, when using a single cell you can consider the cell midpoint to know the required bellows. With my Symmar 360 convertible, when converted to 620mm I need more bellows than 620mm because the lens is at the rear of the lens board. Instead, if I use the front cell only, then required bellows draw is shorter.

Drew Bedo
30-Jul-2017, 17:11
Did the OP get his question answered to his satisfaction?

drew.saunders
31-Jul-2017, 08:54
The distance commonly quoted is the Flange Focal Length of the lens.
That's the distance from the film to the lensboard when focused at infinity, i.e. the bellows draw.
You'll find that on every lens datasheet.
it may be substantially different from the lens' focal length

- Leigh

Fortunately, the Ebony web site is still up, so this page is still available: http://www.ebonycamera.com/articles/lenses.html Hopefully it'll be available for a long time.
It has the flange focal distance for many modern lenses. It helped me decide between the Fuji 300/8.5 vs. the Nikon 300/9 back when both were available new, as I could benefit from that wee bit shorter FFD from the Fuji for the camera I was using at the time (a Tachihara).

Leigh
31-Jul-2017, 12:39
Fortunately, the Ebony web site is still up, so this page is still available: http://www.ebonycamera.com/articles/lenses.html Hopefully it'll be available for a long time.
It has the flange focal distance for many modern lenses. It helped me decide between the Fuji 300/8.5 vs. the Nikon 300/9 back when both were available new, as I could benefit from that wee bit shorter FFD from the Fuji for the camera I was using at the time (a Tachihara).The Flange Focal Length (FFL) aka Flange Focal Distance (FFD) is a critical parameter in determining whether a particular lens is suitable for a particular use on a particular camera.

Lots of particulars, but they are certainly relevant.

My lens database includes that and other information on most modern lenses (except Schneider, which I dislike).

- Leigh

Pawlowski6132
1-Aug-2017, 13:00
Did the OP get his question answered to his satisfaction?

He did. I finally rolled up my sleeves and got a calculator and worked through some equations.

In fact, I was able to put them into practice. I had a group shoot yesterday. Based on my new found knowledge I was able to set up camera, seating arrangements, etc. in advance. By the time the group sat down, all I had to do was fine focus.

than

plaubel
1-Aug-2017, 15:28
Can someone point me to some resources I can study?

For example, Plaubel LF handbooks contain every formula needed for LF.

Best,
Ritchie

aluncrockford
2-Aug-2017, 14:54
As ever there is always an app

https://itunes.apple.com/gb/app/reciprocity-timer/id459691262?mt=8

Pawlowski6132
3-Aug-2017, 18:16
FWIW, instead of an app, I created a handy table I can keep in my bag or pocket.167818