Focus and recompose

[Stan98103]

Do you focus and recompose with long lenses wide-open?

There is an interesting article on focus-recompose problems at the link below. Although it refers to autofocus on SLRs, I think it may be relevant to rangefinders as well. A 90mm lens at f/2.8 and 5 feet only has a depth of field of 1.5 inches.

What do you think?

http://www.visual-vacations.com/Photography/focus-recompose_sucks.htm


Stan

 

[Doug]

Do you focus and recompose with long lenses wide-open?

Stan, I sure do! Even with short lenses wide open, which could be a worse problem, trigonometry-wise. With a longer lens I'm generally far enough away from the subject that shifting the in-focus object a few degrees won't make much difference, and if I think of it I can pull back a bit. And I avoid razor-thin DoF anyway, so for me there's a little margin. The more important issue, I think, is that I don't want to leave the focus point at the center of every composition, and I'm willing to take a small risk on focus to avoid that!

 

[Stan98103]

Doug, I think the link was addressing portrait work where shallow depth of field and long lenses are generally favored. Even though shorter focal length lenses have greater depth of field wide open, you may be right about the trigonometry involved if there is a substantial change in the angle and thus the distance to the object after recomposing. Right now, it’s too late for me to do the math.

Stan

 

[RML]

I do it often but hardly ever (never?) at f2 or so. More likely at f5.6 or up. That way at least I'll have the DOF to cover any mistakes in distance guesses.

 

[wyk_penguin]

Taking pictures is always full of comprimise. I would allow a bit of softness than to have to crop my pictures everytime and be restricted to wide angles.

If it were so critical, everyone would be using large format and focusing on ground glass.

 

[VinceC]

I nearly always try to focus and recompose, unless I'm in too much of a hurry with moving subjects. I haven't had a sharpness problem with old Nikkor lenses.

The focus issue described in the linked article mainly affects high-end flat-field aspherical lenses, copy lenses and darkroom enlarger lenses. My understanding is that all of these are optimized for photographing postage stamps and brick walls wide open but not for capturing the human vantage point -- our viewpoint is spherical: something in front of our nose is closer than something an arm's reach away off to one side or the other.

Nearly all non-asphereical lenses -- ie, all but the very high-end Leica and Cosina lenses -- have a spherical zone of focus that creates no harm when you focus then recompose. The focus point isn't a plane but a bubble. I'm not into Leica or Cosina lenses, so I have no idea how they handle this issue. Classic lenses from Leica, Nikkor, Canon and others should all place you safely in a sphere of sharpness that allows you to focus to a particular point, then pivot to your heart's content while staying focused at that specific distance.

This is actually a bigger issue for fast normals and wides. If you tried to focus a flat-field 35mm lens at f/2 at a distance of 3 feet, there would be a significant change in focus when you recompose.

 

[ClaremontPhoto]

Why would 'wide open' create any sort of a focus issue on a rangefinder?

It is out of the equation.

 

[pvdhaar]

I have a philosophy about it, and it goes like this:

If the lens is long, and DOF is shallow, then the change in angle is so small that the change in distance still falls inside DOF.

If the lens is short, and the change in angle is so large that the change in distance is large, DOF is so deep that the change in distance still falls inside DOF.

Notice a pattern here? I did... I never fuss about it, and it's never bitten me.. Not at 24/2.8 nor at 50/1.8 and neither at 135/3.5 or anything in between.

 

[flipflop]

I have never had a problem with this. I use the contax G camera press the shutter half way down, lock focus, recompose and the press the shutter all the way down. Its quick painless and works very well for me. With the 90mm if I am super close I will usually stop down a little f/4 or maybe 5.6.

 

[Bobbo]

I've never really had this problem before, even on my 10D with a 200mm lens at 2.8, and it's the fastest 200mm lens for less than $3000. I'll have to get the obscenely rare Nikkor 300/2 and see if I can show this problem...I think I hear GAS calling🙂

 

[payasam]

Never had a problem not of my own making. Sometimes in so much of a hurry (see Vince's post) to focus and fire that re-composing is given the go-by. What suffers is composition, not focus; and this seldom happens when using wide to medium long lenses close up and at full aperture. Kicking one's own backside is not an enjoyable activity.
[EDIT] Failing vision has been making focussing more and more difficult, but it's not on to use that as an excuse.

 

[jano]

I've seen this come up on other boards in the past year or two. The resulting conclusion: the article is actually inconclusive. The actual difference in length is minimal.. this may actually apply to seated portraits, not any other kind because they are rarely shot "flat" at 90 angles... not to mention natural human tendency to "sway" (from the portraitee's stand point) which makes the focus point item moot, etc.

With my dSLR, I do use focus points to focus (it was natural habit), but with rangefinder, it's obviously focus and recompose. I rarely see a difference, but sometimes, when on tripod, I do with the rangefinder could have other areas of focus 🙂

 

[David Goldfarb]

Focus-and-recompose is the only option if I'm using the rangefinder on my Technika, because the rangefinder is separate from the viewfinder, so yes, I do it all the time on 4x5" even if I'm shooting wide open with a fast or long lens. This is true of most press cameras that have rangefinders.