IT’S NOT just the kit that gets bigger in large format, practical difficulties can be magnified, too.
This was driven home to me while I was checking some night shots I took with the 6×9 film back on my Crown Graphic. Despite my best efforts to avoid it, the bright lights were still slightly blurred by camera shake.
I guess most people would be pretty happy with the shot – hung on the wall as a 10×8 it would look pretty good – but if you are shooting medium or large format film you really want something better than that. After all, 35mm can look excellent at 10×8 as well.
Still, encountering problems can be a good thing if they make you think about what has happened, why and how you can improve your technique to try to overcome them.
This is the photo….
It is an exposure of somewhere around 30 seconds on Reala 100 film, probably at about f/14. I’m not sure about the lens, it could be a 105mm, a 135mm or 150mm. I held something in front of the shutter as I triggered it, so that any shake wouldn’t be recorded and did the same again when I closed it.
I had reckoned that since the old-timers used this sort of camera for very long-exposure landscapes it should be able to get sharp images in this shot. Now I’m not so sure.
The basic problem is that the bright lights are very, very bright compared to the overall brightness of the main subject. They are over-exposed, of course, but that doesn’t matter. What matters is that they may be more than seven stops difference between the lights and the museum wall. That would be more than 128 times brighter. That means that if the camera shifted for just a quarter of a second during a 30 second exposure, it would be enough to burn a fully exposed unwanted image of the lights into the negative.
Compare that with the situation facing an Ansel Adams wannabe shooting the desert in Utah. The difference between his main subject and the brightest part of the image is probably only two or three stops. If his camera wobbles or is jerked to the wrong position for a whole second during a 30 second exposure it will probably not be enough to create an unwanted second image, as the brightest part of that will be two or three stops underexposed.
It follows from this that very long exposures will tend to mask the effects of a momentary wobble, such as that caused by shutter-slap, unless there is an extreme brightness range.
A second issue is the focal length. Larger negatives require longer lenses to get the same image. Obviously, the longer the lens, the bigger the image displacement if it shakes. Countering that is the fact that the negative itself is larger, so the actual blurring of the image will probably be the same with a 40mm lens on a 35mm camera and a 110mm lens on a 6×9 negative.
That means that enlarging the 35mm camera’s image and the 6×9 image to the same size will result in the same amount of blurring on the print. Where the larger format suffers is if you try to enlarge it to a size bigger than you would do with 35mm – which, surely, is one of the main reasons for using the larger format. Of course, a 110mm lens on a 4×5 inch negative would be much more wide-angle than the same lens on 6x9cm (2×3 inches) so the double image would extend across a smaller percentage of the negative’s width (just as it would if you used a wider angle lens on a small camera).
So a given shake will create an identical amount of blur regardless of format for images which record identical angles of view. Therefore greater care is needed to get acceptable sharpness in larger format than in smaller formats, in order to be able to produce bigger enlargements that will withstand close scrutiny.
In practice, this means large format night photography in a city requires windless conditions, a very solid tripod and extreme care to avoid jolting the camera at any point during exposure, particularly when opening and closing the shutter (holding something black in front of the lens at those moments is a good idea).
However, in daylight very long exposure times will tend to minimise blur from a momentary shock, such as the shutter activating – the longer the exposure the less it will matter.
Can anyone add further suggestions?