Printable View
This is not a question for landscape photographers.:-) I am talking about when the light from the lens is really off axis, such as when you have your 90mm shifted 2 inches, or your 110/120 shifted 4 inches on 4x5. This seems to defeat wide Fresnels, which are otherwise great for head on shots with wide lenses. Do things like Maxwell screens help in this situtation? Is there a Maxwell screen users out there who uses extreme wide angle movements?
The absolutely best solution for wide angle (which is the same as "steep angle") is to use a specially designed fresnel which is stronger than the universal fresnel. I don't use e.g. the Super Angulon 47XL, but even without any shift, the corners should suffer from the same problems which you describe.
//Björn
The only way I handle extreme off axis ray situations is to use a tilting loupe. Even that is a poor solution since the best focus on the GG occurs along a single line within the depth of focus of the loupe. But still it's the best solution I've found when you need to go beyond the widest angle fresnel. I don't think a 4 inch shift and a corner view will be handled by the widest Maxwell screen. My 110 SSXL with a 4 inch shift on 4X5 is a near impossible situation due to light falloff and less than stellar sharpness at the corners.
Nate Potter, Austin TX.
Nathan is right-
a tilting loupe, or at least, a tilted one, is the only way I can do it with 47xl, and the 72xl with movements-
and that's on a standard Arca fresnel-
On bright sunny day outside it's not big problem - you can deal with it.
In studio or dim lighted places, another story:
On Sinar(P2/F2) I use bino viewer (which has mirror angle control adjustement) + standard fresnel. It won't cover whole image at once with 72mmXL + center filter or Nikkor 65mm with movements, but at any given angle I can see part of image and varying angle covers whole image.
In studio sometimes I also use MF digital back for focusing & exposure (and then load film holder:))
I have Linhof TK for field, and on that thing using wides is royal pain cause there's no bino viewer, neither can it take sliding digital back holders. Tilting loupe & luck is all that you can count on. Overall it's up to your camera/accessories design and time you have for framing & focusing. I do quite a lot of portraiture and time is limited.
Thanks for info on tilting loupes! I have been thinking about one, but did not want to spend the money without a report that they helped.
Bjorn - While the WA fresnels work better head on, they actually make things worse off axis. I had to pull mine on my Ebony because I just could not see what I was doing way off axis. I think they end up being more directional, which means when you get them out of their planned orientation, they do not help.
With my standard Maxwell screen, I can see into the corners of my 47mm Super Angulon using a straight-on loupe. That lens needs a dark cloth and maybe even a little time under it to let the eyes open up a bit, if you want to see into the corners.
That lens is more limiting in terms of viewing than longer lenses with more extreme movements. (My 47 is not an XL and I use it for 6x12, where it is at its limits.)
I am able to compose a 65mm f/5.6 Super Angulon on 4x5 easily with the Maxwell screen, right into the corners of its coverage.
Rick "who'll experiment with a 90/5.6 Super Angulon with huge shifts and report back" Denney
Hey Rick! Let us know about the 90mm. I have no trouble with my 65mm Nikon, but then all I can get is about 1/4 shift and it is f4 lens.:-)
Okay, I just played a little bit with the 90/5.6 Super Angulon. Eyballing it, I'd say I have three inches of shift, right to the edges of coverage. Using a tilted loupe, I could easily focus on interior light sources in rather dark conditions, right at the edge of coverage, with no dark cloth. I measured a lamp that was in the view with my Pentax Spotmeter, and it was EV 5-1/3. With the shift removed and the camera pointed right at the lamp, it measured about 7-1/2. The lamp itself measured 15. The lens was wide open at f/5.6, which, of course, exacerbates the off-axis falloff. I would have needed a laser pointer to focus it at f/22.
Looking at the Maxwell screen straight on, the brightness of the lamp (shifted to the edge of coverage) dropped three or four stops compared to viewing it with a tilted loupe.
So, the Maxwell screen is quite usable at the extreme of the 90, but a tilting loupe is still necessary.
Rick "whose loupe is too bulky" Denney
If you are doing a lot of work with a roughly constant front movement (for example, taking architecture shots with a roughly constant large amount of front rise) you can cut an off-centre section from a larger fresnel.
Say you are working in 4x5 with two inches of front rise. Mentally imagine you have an 8x10 back on the camera with some kind of reducer that puts the 4x5 film in the right place. What you want is to cut out the section of an 8x10 Fresnel that corresponds to where your 4x5 film is.
Don't get hung up on the 8x10 size: the real problem is that the optic axis of your lens is not aligned with the optic axis of your Fresnel. Cutting an outer section of a larger Fresnel lets you align the axes again. The only problem is knowing which section to cut, and that's why you need a roughly constant set of movements (unless you want to carry a whole bunch of Fresnels for different cases).
Of course, good large Fresnels are expensive, but a whole page magnifier gives enough offset for 4x5 to provide a useful composing tool - just pop it out when you want to fine-focus.