If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#71
|
|||
|
|||
High resolution photos from a digital camera.
"Scott W" wrote in message oups.com... Second, for a telephoto lens, the nodal point can be VERY far in front of the lens. Of course, the later can be accomodated using an offset camera mount. Well the nodal point can't be way in front of the lens Perhaps we have a confusion of terms. Are you thinking of the Entrance Pupil? Telephoto lenses are, by definition, physically shorter than their focal length. The front nodal point can be in front of the lens. Yes, outside the lens. |
#72
|
|||
|
|||
High resolution photos from a digital camera.
Lorem Ipsum wrote:
"Scott W" wrote in message oups.com... Second, for a telephoto lens, the nodal point can be VERY far in front of the lens. Of course, the later can be accomodated using an offset camera mount. Well the nodal point can't be way in front of the lens Perhaps we have a confusion of terms. Are you thinking of the Entrance Pupil? Telephoto lenses are, by definition, physically shorter than their focal length. The front nodal point can be in front of the lens. Yes, outside the lens. It can't be very far out. Trace some rays, they have to go through the nodal point and then hit the main objective lens. The diameter of the objective lens limits how far out the nodal point can be. Also paralax is less of a problem with longer lenses in any event, it is aways the short FL shoots that are tricky. Scott |
#73
|
|||
|
|||
High resolution photos from a digital camera.
"Scott W" wrote in message oups.com... Telephoto lenses are, by definition, physically shorter than their focal length. The front nodal point can be in front of the lens. Yes, outside the lens. It can't be very far out. Trace some rays, they have to go through the nodal point and then hit the main objective lens. The diameter of the objective lens limits how far out the nodal point can be. The nodal point is so far from the default tripod mount that one had better take it seriously. Also paralax is less of a problem with longer lenses in any event, it is aways the short FL shoots that are tricky. And to exacerbate that, there is edge distortion in most wide lenses. |
#74
|
|||
|
|||
High resolution photos from a digital camera.
Lorem Ipsum wrote: "Scott W" wrote in message oups.com... Telephoto lenses are, by definition, physically shorter than their focal length. The front nodal point can be in front of the lens. Yes, outside the lens. It can't be very far out. Trace some rays, they have to go through the nodal point and then hit the main objective lens. The diameter of the objective lens limits how far out the nodal point can be. The nodal point is so far from the default tripod mount that one had better take it seriously. I use a panoramic head, it rotate the camera around the nodal point in both axis. Also paralax is less of a problem with longer lenses in any event, it is aways the short FL shoots that are tricky. And to exacerbate that, there is edge distortion in most wide lenses. The software adjusteds for that fairly well, still wide angle shots need much more care. Scott |
#75
|
|||
|
|||
High resolution photos from a digital camera.
In rec.photo.equipment.35mm Scott W wrote:
It can't be very far out. Trace some rays, they have to go through the nodal point and then hit the main objective lens. The diameter of the objective lens limits how far out the nodal point can be. Now consider the angle of view of long tele lens... Scott -- Sander +++ Out of cheese error +++ |
#76
|
|||
|
|||
High resolution photos from a digital camera.
"Perhaps we have a confusion of terms. Are you thinking of the Entrance
Pupil? " When shooting multi-image panoramas you need to rotate about the entrance pupil, not the nodal point. This is because the center of perspective is the entrance pupil. In telephoto lenses the entrance pupil is almost always either well inside the lens, and in many cases is *behind* the lens, not in front of it. Offset camera mount? Maybe, but offset in the opposite direction to what you are thinking about. Brian |
#77
|
|||
|
|||
High resolution photos from a digital camera.
"BC" wrote in message oups.com... "Perhaps we have a confusion of terms. Are you thinking of the Entrance Pupil? " When shooting multi-image panoramas you need to rotate about the entrance pupil, not the nodal point. This is because the center of perspective is the entrance pupil. In telephoto lenses the entrance pupil is almost always either well inside the lens, and in many cases is *behind* the lens, not in front of it. Offset camera mount? Maybe, but offset in the opposite direction to what you are thinking about. At last, a source of authority. Brian, so many QTVR and other documents specifiy 'nodal point', but then talk about something else. I confess to being confused, and I appreciate the clarification. |
#78
|
|||
|
|||
High resolution photos from a digital camera.
Lorem Ipsum wrote: "BC" wrote in message oups.com... "Perhaps we have a confusion of terms. Are you thinking of the Entrance Pupil? " When shooting multi-image panoramas you need to rotate about the entrance pupil, not the nodal point. This is because the center of perspective is the entrance pupil. In telephoto lenses the entrance pupil is almost always either well inside the lens, and in many cases is *behind* the lens, not in front of it. Offset camera mount? Maybe, but offset in the opposite direction to what you are thinking about. At last, a source of authority. Brian, so many QTVR and other documents specifiy 'nodal point', but then talk about something else. I confess to being confused, and I appreciate the clarification. I have to confess I was also confused about this issue a few years ago, because I really hadn't thought it through. Like you say, an awful lot of web sources say you should pivot about the nodal point. Even sources that should know better, like Kaidan, make the same error. But then I tried a simple experiment to demonstrate that the correct rotation point is indeed the entrance pupil. First, I used parallax to determine the rotation point for my 50mm f/1.4 lens - stopped way down of course. Then I moved the entrance pupil by moving the aperture stop: I opened the lens to f/1.4 and placed a piece of tin foil with a small hole in front of the lens. Sure enough, the new rotation point (determined experimentally) had moved forward by the same amount the pupil had shifted. The nodal points are completely independent of stop location, so the entrance pupil is clearly the correct rotation point. In a sense it really doesn't matter, and for most people its just pointless technical semantics. After all, the parallax method commonly used to find the correct rotation point is very accurate, and doesn't require that you understand the underlying optical principles. Brian |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
High resolution...through digital interpolation... | Des | Digital Photography | 256 | April 18th 05 02:51 PM |
Price War Hits Digital Photos | MrPepper11 | Digital Photography | 3 | March 19th 05 12:32 AM |
digital camera storage conundrum - Answered! | [email protected] | Digital Photography | 0 | January 12th 05 02:51 AM |
FA: Panasonic Lumix DMC-FZ1 Digital camera with Leica 12X optical zoom lens | Marvin Culpepper | Digital Photo Equipment For Sale | 0 | October 15th 04 01:05 AM |
Which is better? digital cameras or older crappy cameras thatuse film? | Michael Weinstein, M.D. | In The Darkroom | 13 | January 24th 04 09:51 PM |