Proper shading of LF and ULF lenses

[Robert A. Zeichner]

I have been experimenting with some new ways to shade lenses more effectively and have run tests confirming my suspicions. The results are in my latest article in the March/April issue of Photo Techniques magazine, pages 33-34. This should be of particular interest to those using ULF cameras with older lenses that have huge coverage as well as those using panoramic formats, where the light outside of the image area often exceeds the picture area! With excess veiling glare reduced significantly and and bellows flare eliminated altogether, negatives will exhibit better contrast and appear sharper.

[GPS]

I don't have access to your article but I use my own lens shades that I construct (calculate) for each of my lenses and format. I discovered that speaking about effective lens shades with the majority of amateurs is a lost time - you will mostly get the "I use my T-shirt" answers... Yet an efficient lens shade is more important for the picture result that multi coating itself.

[Daniel Grenier]

Can you both briefly describe your findings and procedures here, perhaps?

[darr]

Robert,

I appreciate your article (I have read it), but I must say that in the copy I received, one can not really see that much of a difference between the resulting prints. It was best that you described your findings in the article because the photos printed do not show a difference in contrast larger enough for me to give up on my Lee system. You are definitely a creative soul to put together a contraption that includes barn-doors, velvet paper, and hair scrunchies.

Best,
Darr

[Ash]

I have a 52mm filter size rubber lens hood from an SLR lens. I use a bit of tape to attach it to uncoated barrel lenses.

This has worked fine. Yesterday I had a studio flash at about 90degrees, 3-4feet from the lens, so without a lens it would have flared over the whole image probably. The image came out fine. the hood is also wide enough and shallow enough not to cut out any coverage.

[Juergen Sattler]

I finally invested in a Lee Hood with slots for filters whch I can use on all my cameras from 35mm all the way to 8x10. The Lee filters and hoods are pricey, but I figured that it is justified, given its usefullness and the fact that I can use it for all my gear. It works great, esp. with split density filters.

[Stephen Willard]

Robert, I read your article a few days ago about shading the LF lens. In my issue I saw a notable difference between the prints and the differences were significant. I do have a few questions for you.

1. If the front element of the lens is completely shaded without the use of a lens hood, do you still need to use one? A good example would be when the sun is behind you.

2. What is the difference between using barn doors and an adjustable lens hood such as the Lee lens hood?

Any considerations would be greatly appreciated.

[stompyq]

I don't suppose theres a link to this article is there? I am very intrested in it. I normally do not use hoods b/c most of the time i use a cokin filter holder with singhrays.

[Robert A. Zeichner]

Robert, I read your article a few days ago about shading the LF lens. In my issue I saw a notable difference between the prints and the differences were significant. I do have a few questions for you.

1. If the front element of the lens is completely shaded without the use of a lens hood, do you still need to use one? A good example would be when the sun is behind you.

2. What is the difference between using barn doors and an adjustable lens hood such as the Lee lens hood?

Any considerations would be greatly appreciated.

Stephen, these are both good questions. The first thing that needs to be pointed out is that photographic lenses have conical fields of view. Out of the rear of the lens is a similar conical projection. The target (film) is rectangular and when calculating that portion of the image circle that lies outside that rectangle, we discover that a considerable percentage of the light passing through the lens never touches the film. As an example, a format that is twice as wide as it is high will be struck with only about 50% of the projected cone of light exiting the rear of the lens. All of that non-image-forming light bounces around inside the lens and depending on the vintage of the optic, whether or not it is coated, multicoated, well baffled or not, that extra light contributes to veiling glare which reduces contrast. Unless you aim your camera at a rectangular subject that is the same proportion and orientation as the film, beyond which is a background of jet black, there will always be some light striking the lens that has nothing to do with what hits the film. In a worst case scenario, there will be bright open sky or beach sand or snow that lies outside of the desired image. Even on overcast days, it is a mistake to assume that because there is no bright sun, that light colored objects lying outside the image area can't contribute to increasing veiling glare. They will and they do. So, the short answer to #1 is yes, you need a shade, preferably a rectangular one that lets only image forming light reach the lens.

One other factor to consider is that light that is outside the image area can strike the inside of the camera's bellows at shallow angles. This can actually cause bellows flare which will kill contrast as well. Using the BD shade eliminates light from hitting the bellows at all.

In answer to #2, I'm not intimately familiar with the Lee hood, but I can tell you that unless it allows you to change the aspect ratio of the shaded opening and unless it allows you to compensate for off center images where some shift and rise/fall have been used, it can't be as effective as the barndoor shade. The adjustability of the leaves of the barndoor automatically allow you to compensate for different formats and movements.

I was simply astonished at the difference in the negatives I made using the BD shade vs. the round shade and in just about every lighting situation and with every lens I tried. I won't ever again be without my BD shade. I'm just sorry it took me so long to come up with something this simple and effective.

I hope that helps.

[Robert A. Zeichner]

Robert,

I appreciate your article (I have read it), but I must say that in the copy I received, one can not really see that much of a difference between the resulting prints. It was best that you described your findings in the article because the photos printed do not show a difference in contrast larger enough for me to give up on my Lee system. You are definitely a creative soul to put together a contraption that includes barn-doors, velvet paper, and hair scrunchies.

Best,
Darr

Darr,

I received three issues of the magazine from the publisher and in all three, the reproductions clearly show the difference. The printing process is an imperfect one and is often subject to variation, so I won't dispute that your issue doesn't reveal much of a difference. The attached files might better demonstrate what I am talking about in the article. Look at the detail inside the darkest cavity of the stump and also the rocks just below that area. Also the fence in the upper right.

As far as my contraption, what can I say? Perhaps I've been watching too many McGyver(sp)? re-runs.