How do you test your focusing/equipment

[sully75]

Is there a good test for checking your focusing skills and your rig? I'd just like to know that I have everything zero'd in. Should I focus on the 6" mark on a ruler wide open? A fence? I guess both of those would work but anyone have anything classier?

[Lynn Jones]

Yes, make a significant enlargement!

Lynn

[Dan Fromm]

Paul, it helps to have the target at an angle to the film plane, with the target's intersection with what you think is the plane of best focus well marked (don't rely on memory, mark it well) and to focus back and forth through it several times. It also helps to have a target with fine enough detail from a good distance in front of the intended plane of best focus so that you'll have a chance of estimating where the plane of best focus really is when you examine the negative at high magnification.

Why are you asking? I ask because every once in a while I miss focus consistently. I never know it until the film's processed. When it happens I curse a bit, then set up and test. The results aren't surprising, given that I haven't replaced focusing panels or film holders for quite a while. So far, the problem's always been me, not a discrepancy between the front of the ground glass and the film plane that has just magically appeared.

[ic-racer]

Is there a good test for checking your focusing skills and your rig? I'd just like to know that I have everything zero'd in. Should I focus on the 6" mark on a ruler wide open? A fence? I guess both of those would work but anyone have anything classier?

I find "infinity" to be a better target.

For 'zeroing' the detents, the shorter the lenses you use, the more critical it is. For example, my experience is that a 65mm lens on a 4x5 camera needs to have the detents zeroed from right to left with what I estimate to be one-half the precision of a Hassleblad lensmount to get the horizon at infinity in focus from the far right to the far left. I aligned the detents on my Horseman 6x9 and Horseman 4x5 FA using a laser.

[Leigh]

For 'zeroing' the detents...

What detents?

- Leigh

[TheDeardorffGuy]

I have Deardorffs. The only detent is the rear tilt. I check the squareness to the bed with a machinest square. Check. Then open the lens and square the front by eye or square. I focus on power lines that are about a mile away. Can I detect the insulators holding the wires? How about the branches of trees in the winter? Do they seperate? And then you should take a picture and realize it does not make a difference unless you do not like the print.

[Vaughn]

I exposed negatives and make prints. If I like the print, everything must be just fine.

Vaughn

[Brian Ellis]

I don't think I've ever made a focusing test but if I did it probably consisted of putting a sheet of newsprint on the wall and making a couple photographs.

One of the reasons I haven't found it necessary to test is probably the fact that with the landscape and architecture work I typically do, and at the smaller apertures I typically use, depth of field tends to fix any focusing errors that would be cured by adjustments to the camera on the order of a few mms or less. With many photographs I don't even remember exactly what I focused on - was it that leaf on the left or the bark underneath it? - so I wouldn't know if there was a focusing error or not unless everything in the photograph was out of focus, in which case the problem almost certainly was me, not a matter of making some camera adjustment by a matter of a few mms. And even if I did get everything on the camera adjusted and lined up to perfection I know the film holder doesn't hold the film perfectly flat so I'd still be off by some unknown amount. I don't know, I certainly don't mean to put down anyone who conducts focusing tests. I just haven't found a need to do so that I recall.

Of course if I consistently got the same focusing mistake - e.g. I was a portrait photographer and every time I focused on someone's eyes I got the tip of their nose in focus instead - that would be a different matter but I wouldn't need to test to find that kind of thing, I'd know from looking at my photographs.

[E. von Hoegh]

I make certain that my filmholders are within spec., yes I check every single one with a depth micrometer; perform the same check on the groundglass, and take photographs. I use a 10x Peak loupe to focus, it has a removeable skirt for looking into the corners with a wide-angle lens.