Stupid question about lenses, vignetting, groundglass illumination

[Leigh]

yes but strobes change the look totally ...

It doesn't have to. It's all in how you use the lights. It can look every bit as natural as sunlight through a window.

- Leigh

[Leigh]

BTW, your ground glass may have the corners clipped. That's so you can peek through and see that area is still getting light from the lens...

Actually the corner bevels are just to permit free airflow as you adjust the bellows.

- Leigh

[Gem Singer]

Leigh,

Allowing the air to enter or escape the bellows, when it is expanded and contracted, is only one function of the clipped corners of the ground glass.

The most handy function is allowing the photographer to look into the camera through a clipped corner opening and check to see if the lens is stopped down sufficiently to cover the format, thus preventing vignetting.

When looking at the lens opening wide opened, the aperture appears to be football shaped.

As the aperture is closed down the football shape becomes round (the shape of the lens's iris) indicating that the aperture has been closed down to a point where vignetting no longer occurs.

[Noah A]

The Apo-Sironar S 240mm was my favorite lens when I was shooting 8x10. It should serve your needs very well.

I didn't hesitate to shoot it at fairly wide apertures, maybe even f/8-11, for interior portraits. Often with 400NC that would give me usable shutter speeds. I don't have any of that work online, but maybe I'll re-scan some of it and post it.

I was often doing portraits in the range of 1/8th of a second to 1 second.

I was doing single portraits though, not families. That would be tougher.

I know it's expensive, but you will just need to do some experimentation. Perhaps you could get some cheap B&W film, or even use paper negs, for some tests...

I've actually never used a camera without a fresnel, but I imagine one would help. Still, the darkened corners on the groundglass don't necessarily correspond to what you'll get on film. When shooting my 80mm lens on my 4x5, the corners are very, very dark on the GG. And while there is falloff with that lens, it's not nearly as bad as the GG would have one believe, even with a fresnel.

You also may need to move your head around...if you look at the corners of the frame from an angle you can sometimes get a brighter view. And the clipped corners are very helpful for checking coverage.

There's a difference between natural light falloff and mechanical vignetting. So it's definitely smart to check for the latter by looking through the clipped corners of the GG to see if the aperture is round. The 240 doesn't allow for a ton of movements, but I found it offered enough coverage for most uses.

[DaveTheWalker]

Wow, this thread explains a lot! I was just doing a search to try to find out whether the pronounced bright spot was just down to my setup or more universal. Thanks to all for the explanations.

Time to sort out a decent dark cloth...