do you focus with filters on?

[Andrea Gazzoni]

how do you usually focus? filters on or off?
thank you for any suggestion
andrea

[Andrew O'Neill]

I focus with filters on... except when I'm using an opaque filter such as #87 for infra-red photography.

[BrianShaw]

Yes, generally. Always with screw-on or slip-on filters, but not always when using gel filters.

[Gem Singer]

My routine: take a meter reading while holding the filter in front my Pentax digital spot meter lens.

Then, screw the filter onto the camera lens and focus on the ground glass using a loupe.

My answer to your question is YES.

[Ari]

No, I don't, and I've never seen a problem in my negs.

[Brian Ellis]

There are lots of interesting possibilities when using filters and focusing. Ideally I remember as I'm setting up that I'll be using a filter so I put the filter on as soon as the camera is on the tripod, then focus with the filter on. Another possibility is to get all set up and ready to go, then remember the filter. When that happens I don't bother to refocus, I put the filter on and shoot. I haven't seen that either way makes a difference.

But unfortunately there are other possibilities. One that I like is to forget to put the filter on until after the exposure is made, then remember that I based the exposure on using a filter, in which case I throw away the first sheet of film, put the filter on, and make a second exposure, usually without refocusing.

Another, which is my personal favorite, is to forget the filter and also forget that the exposure was based on using a filter until I process the negative and see how badly it's underexposed.

[Emmanuel BIGLER]

how do you usually focus? filters on or off?
thank you for any suggestion
andrea

Hello from France !

When taking pictures of far-distant objects with a good quality filter with plane and parallel surfaces there is in principle absolutely no focus shift when the filter is located in front of the lens. Hence I always focus with the filter on (I've never used dark ND filters or dark red "infra-red" filters). For this kind of visually opaque filters used in front, no focus shift, I would simply focus without filter a usual and attach the filter just before taking the picture.
However, for some large-size view camera lenses, it might be more convenient (a smaller filter being be cheaper) to use a smaller size filter attached to the rear of the lens.
In this configuration, there is a backward image shift depending on the filter material and filter thickness (see below). For an ordinary glass of refractive index 1.5, the image shift is equal to 1/3 of the glass thickness.
The question was recently raised, not later than yesterday (!!) by a friend of mine who wished to use a dark ND filter on a large wide-angle view camera lens.
Setting the filter at rear would save some $$$ with a smaller filter, however, since, at rear, you have in principle to focus with the filter in place, to compensate for the image shift, with a dark ND filter you won't see anything on the ground glass ... you could of course imagine to calibrate the proper image shift and apply it "mechanically" after focusing without the filter .. but doing so we a entering a time-consuming procedure (I can already hear all DSRL users laughing out loud ! "the guy insists on using a cumbersome view camera and pretends that he dislikes slow procedures !! ah ah !!") :D

Regarding using filters at the rear of the lens, the image shift is a constant independent on the position of the object an image, it is a constant value proper to the fllter combination of glass (or gelatin) filter thickness "t" and refractive index "n" ==> shift = t.(1-1/n) (yields t/3 when n=1.5)

[Sirius Glass]

I focus with the filter on unless the filter makes it too dark to easily focus, then I focus without the filter, lock the focus, put on the filter.

[Armin Seeholzer]

No, I don't, and I've never seen a problem in my negs.

For the front ist dos'nt matter, if I use one behind then I fokus with it!

Gruss Armin

[Heroique]

My Lee system determines my most common habits…

Filters are off for focusing & movements (including filter rings, holder, shade).

Protection filter, always on – but usually never on in calm conditions.

Entire filter system + shade is on, when checking corners; if it’s a difficult shot, fine-tuning focus & movements are sometimes necessary at this point.

Exceptions apply. ;^)

[Peter De Smidt]

Like Armin, I focus without the filter if I'm using one on the front of the lens. If it's on the rear, I focus without it, note where the plane of focus is, put the filter on, check if it's still on the same plane, and then refocus a tiny bit, if needed.

[ImSoNegative]

no i never have,