Bellows Compensation for Landscapes

[Robert Oliver]

I like my ruler idea better. just put the pre-marked ruler on the side of the camera determine whether or not I need exposure compensation. Place the ruler's 0 end at where the film plane is and note where the lensboard is (doesn't have to be 100% accurate. (telephoto lenses need different measurements) I marked the ruler for infinity and at 1/2 stop intervals until it's 1:1. Each lens has it's own marking on the clear plastic ruler. Light, easy and most of all brainless and quick. Great in fading light and light breezes.

Seems kind of like a hassle to put a disk on a subject and measure it's size on the GG. Might be more accurate but seems like a pain.

[Bruce Osgood]

You'll see slightly differing numbers regarding how close you can be to the subject before compensation is needed, but a distance of ten times the focal length seems to be safe.

I think you are correct. The math for factoring the exposure is:

Lens Focal Length^2 / Bellows Length^2

Where: LFL = 5" (25) / BL = 10" (100) Compensation would be 4 stops.

Rounding is acceptable as it is not a precise issue -- good enough for government work.

[David A. Goldfarb]

There are lots of methods for determining bellows factor. I have the magnification table in the attachment taped to all my cameras and in my notebook. I usually estimate the magnification factor by comparing the width or height of the scene at the subject position to the width or height of the format visible on the groundglass, or if I need to be more precise, I'll put a ruler in the scene and actually measure it on the groundglass to determine the magnification factor precisely, then I look up the bellows factor on my table and calculate it into the exposure.

This method works with any lens, any format, any camera, requiring no new calculations for new lenses (as rulers do) or scaling up or down (as the QuickDisk and square version that Calumet sells, which only work on cameras that have an accessible groundglass of sufficient size and with scenes that are larger than the disk or square itself).

[Photojeep]

Bellows compensation only comes into play when the bellows draw is longer than the focal length of the lens.

I teach large format photography and this is the most mis-understood and mis-used bit of information in photography. To simplify it, I tell my students that if they are shooting anything outside other than a flower or similar close up, they will not need any compensation. I also tell them that EVERY TIME they shoot their large format camera indoors, they will need to compensate for bellows extension.

Best regards,
Randy

[Leonard Evens]

I have used the Quickdisc for close-ups when I had an RSW and still use one with my SU. They are so simple and accurate to use, even for E6, all you need is some blutack for windy day.. and possibly laminate for when it is wet. I don't see why people persist with the maths (and I teach it).

You only need to worry, if a key part of the image is very close and you are having to rack the bellows out some way beyond focal length of lens to focus. If bellows extension is modest and you are able to get that part of the image in using movements then you won't need to to apply a bellows factor compensation.

The mathematics has of course already been done by whoever made the Quick disk. But if you know the mathematics, you can make your own quickdisc or use any one of several methods which require minimal effort in the field.

For example, I made a small paper tape which has scales, one for each of my lenses, from which I can read off the number of stops or fractions of a stop correction to apply. I just lay it between the standards and read off the correction. It rolls up into a coil less than an inch in diameter. The advantage it has over the quickdisc is that I don't have to put something in the scene and then remember to recover it before I make an exposure. The disadvantage is that theoretically I should compensate for the difference between the actual focal length and the rear flange focal distance, but since none of my lenses is of telefocal design, that doesn't make enough difference to matter. Also, if I were really concerned about that I could make a simple table from which I could read off the correction based on the shift from infinity focus to the close-up focus measured in mm.

[Daniel Geiger]

I like my ruler idea better. just put the pre-marked ruler on the side of the camera determine whether or not I need exposure compensation. Place the ruler's 0 end at where the film plane is and note where the lensboard is (doesn't have to be 100% accurate. (telephoto lenses need different measurements) I marked the ruler for infinity and at 1/2 stop intervals until it's 1:1. Each lens has it's own marking on the clear plastic ruler. Light, easy and most of all brainless and quick. Great in fading light and light breezes.

Seems kind of like a hassle to put a disk on a subject and measure it's size on the GG. Might be more accurate but seems like a pain.

Yes, the ruler (or tape measure) works great as long as you do not introduce any movements, particularly no tilt. With center tilt it is pretty much fine (as long as you don't do much rise/fall), but with base tilt, you may get some pretty wrong factors, that will show up on chromes. If you compare the quick disk/exposure calculator with the ruler measurements, I have been off by 1/3 to 1/2 f-stop. With bracketing one should be quite fine, but it is worth taking into consideration.

Tele lenses are actually not different for the application of the ruler method, as long as you do a dry-run at home, with quickdisk at particular mag, and then measure the bellows draw. Works great for my Nikor T-360/500/720.

[Turner Reich]

There are lots of methods for determining bellows factor. I have the magnification table in the attachment taped to all my cameras and in my notebook. I usually estimate the magnification factor by comparing the width or height of the scene at the subject position to the width or height of the format visible on the groundglass, or if I need to be more precise, I'll put a ruler in the scene and actually measure it on the groundglass to determine the magnification factor precisely, then I look up the bellows factor on my table and calculate it into the exposure.

This method works with any lens, any format, any camera, requiring no new calculations for new lenses (as rulers do) or scaling up or down (as the QuickDisk and square version that Calumet sells, which only work on cameras that have an accessible groundglass of sufficient size and with scenes that are larger than the disk or square itself).

I opened it an found the scale repeated several times, How does it work? Is it just a scale printed out?

[David A. Goldfarb]

Yes, it's just a scale printed out. I have it duplicated five times on one page, so you can print it out and cut it up and put it on five different cameras or tape it to your light meter or into your notebook or wherever is handy, if you wish.

How does it work? So say you're taking a head and shoulders portrait on 8x10". The width of the format is approximately 8 inches. The width of the field of view at the position of the subject from one shoulder to the other shoulder is going to be about 24 inches--you can estimate this distance or you can physically measure it with a ruler--so the magnification ratio will be approximately 8:24 or 1:3. Look up the ratio of 1:3 in the left hand column of the table, and the bellows factor will be in the right hand column--between 2/3 and 1 stop.

You don't need to think about the focal length of the lens or the length of the bellows with this method. If you decide to shoot 4x5" instead of 8x10", the magnification for an image framed in the same way becomes 4:24 or about 1:6, so your bellows factor for the same composition with a 4x5" camera will be about 1/2 stop.

Most of the time, an estimate of the magnification factor is sufficient. You always know the dimensions of the format, so you only need to estimate the dimensions of the scene in the real world. If you have trouble estimating, put a filmholder in the scene to provide a sense of scale.

[Turner Reich]

Very good that makes sense, I will print out the scales and take them along on the next shoot.

tr

[John Berry]

No correction factor is needed for anything over 8 times the focal length. I learned on this very forum the simplest way ever to find the correction factor. Think of your focal length as an f-stop. If you have an 8 in lens, and your distance from lens to film plane is 11 in, that is one stop. Plain and simple. I don't have to do math or chase my 2" target for my factor scale when the wind blows it away. Do set up the camera and make a reference measurement at infinity. I put the focal length dimension at the back close to film plane and see where it falls in the front standard. That's a defined edge, not hanging in the air in front of the lens board. I start the tape on the front standard at that dimension and measure to the back. No scales, no calculations, only a tape measure as long as the bellows. The paper yardsticks they have at IKEA work hunky dory, and they are free by the handful.