PDA

View Full Version : 90mm lens for objects almost on top of lens?



dh003i
15-Jan-2009, 21:53
These two shots were taken with my Oly E-3 (http://www.tabblo.com/studio/stories/view/1691487/) (a 4/3rds sensor, about half the diagonal as 35mm film). The first one with a the 58mm (I don't know the f-stop, but I'm pretty sure it was stopped down below f/1.2 ;-), the 2nd one at 14mm, probably stopped down to f/22.

In particular, on the second shot, the wind had blown that leaf (which I'd previously placed a little bit further from the lens), practically right on top of it just before timed shot. It was a good accident, imo (although the other leaf that was still in motion was too bad). It appears almost sharp from right on top of the lens to the back-ground (still reasonably sharp).

I've been looking at the Nikkor-SW 90/4.5 or Rodenstock Grandagon 90/4.5 to "complete" my LF lens set, for relatively wide-angle landscape. Will these lenses (with about 102 to 105 degrees of coverage, excess coverage of up to 72mm) be able to provide that kind of depth in the shot, while maintaining resolution (not stopping down to f/64), due to the movements?

PS: In case it isn't clear, I'm asking about the Nikkor-SW 90/4.5 or Rodenstock Grandagon 90/4.5 for the 4x5 format. ;-)

If anyone has some photography showing 4x5 work that incorporates objects both really close to the camera and far away by utilizing tilt, I'd be interested in links.

Mark Woods
15-Jan-2009, 22:09
EXCUSE ME 4/3RDS SENSOR????? This is a forum for LF. I think, if I understand correctly, that the minimum LF standard is 4"x5". You don't mention the format you're interested in. Tilts and Swings can change focus capabilities. The angle of coverage can be determined with a number of sources including ones on this website. Resolution is determined on a number of factors: acuity of film/lens, projection (size of print), and viewing conditions. Acceptable DOF is determined by the format you're working in. 4/3" chip has a great deal of DOF at F/8 while 16x20" DOF at F/8 is considerably less. These are mathamatical relationships you should become aware of befoe posting something like you did. The information is out there.

dh003i
15-Jan-2009, 22:24
EXCUSE ME 4/3RDS SENSOR????? This is a forum for LF. I think, if I understand correctly, that the minimum LF standard is 4"x5". You don't mention the format you're interested in. Tilts and Swings can change focus capabilities. The angle of coverage can be determined with a number of sources including ones on this website. Resolution is determined on a number of factors: acuity of film/lens, projection (size of print), and viewing conditions. Acceptable DOF is determined by the format you're working in. 4/3" chip has a great deal of DOF at F/8 while 16x20" DOF at F/8 is considerably less. These are mathamatical relationships you should become aware of befoe posting something like you did. The information is out there.

Chill out, I'm aware of those things, which is why I was asking the question. I thought it was clear I was asking about the 90/4.5 lenses for 4x5. (I modified the OP to explain that).

The hyperfocal distance for the focal length/aperture at which I took the second shot is ~2 ft, which is surprising to me since that leaf is closer than 1 ft, but still appears quite sharp (even at 1:1 looking at the unsharpened RAW file). The hyperfocal distance for 90mm at f/22 on 4x5 is 12 ft, at f/32 it is 8.6 ft, and at f/64 is 4.45 ft. I'm wondering if the tilt (which I calculate to be about 27-32 degrees, depending on if it's vertical or horizontal) is enough to get those very close objects into focus.

Dan Fromm
16-Jan-2009, 02:55
At 1:1, f/64 indicated is f/128 effective. Might as well use a pinhole.

Joe Forks
16-Jan-2009, 08:03
Here's some articles which should help you quite a bit with your questions.
http://www.trenholm.org/hmmerk/HMArtls.html

These helped me quite a bit.

CG
16-Jan-2009, 09:26
Yes, you can tilt / swing and get very sharp near and far, but I think you will just have to try it and see what works for you. You may find that the limiting factors are rather mechanical; how much you can distort your bellows; how close you get to the edge of the circle of coverage...

Most modern short lenses won't stop down to f128 ... f180 etc, and for good reason, the sharpness really takes a hit at small apertures - so movements are key. You may want to look at 75mm, 72mm, 58mm, 47mm, the really short glass. I don't know that they are better, but if you are looking for the wide angle effects, there's a lot of room on the short side of 150mm for various wide angle possibilities.

Given that, a 90 is a good stepping stone to the 72/75 or shorter lenses, so that you don't have a huge gap between your angles of view. I can see a set of 90, 72, 47mm making good sense.

aduncanson
16-Jan-2009, 10:09
Dan Fromm gave a great answer in a recent thread about the closest focusing distance of a 125mm Fujinon lens. In any lens you can focus no closer than 1 focal length from the front nodal point of the lens. Unfortunately to focus that close you would need a bellows of infinite length (which Dan hinted at, but did not explicitly say.)

So, how did your 14mm lens do the impossible? Two answers come to mind. First, the front nodal point may be buried deep inside of what I suspect is a pretty complicated zoom lens. Second, the lens may well be focusing by a means similar to what was known as front element focusing, commonly employed on old folding cameras. Rather than moving the entire lens as a unit away from the sensor when focusing close, the spacing between elements is adjusted to shorten the effective focal length. Meaning that when focused close, the focal length of the lens is actually shorter than marked.

Dan Fromm
16-Jan-2009, 12:35
Zooms. Ah, yes, zooms. Internal focusing zooms, or zooms that have a macro mode in which moving the zoom group(s) alters the focused distance.

I can't remember which one now, the Angenieux 8x8B comes to mind and so does the thought that I'm mistaken, but there were zooms for S8 cine cameras that would focus on an object in contact with the front surface.

AFAIK nothing like that is available for LF. But I do have a somewhat busted TTH Varotal gathering dust in a closet. I think might cover 2x3 at its longer focal lengths, if I ever get the moving parts to move as they're supposed to.

Cheers,

Dan