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#1
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one unsharp corner on prints? Help!
Hello,
I need some help. I have been making some 8x10 prints from 4x5 slides using my 150mm rodenstock rodagon lens. For the most part my prints are full frame. I am getting one corner that is not sharp and in fact it looks like movement. It always happens in the same corner. I re-aligned my enlarger and assured my paper is laying flat. My easel is totally flat. When I change to my 135mm Nikon lens problem goes away. Prints made with my 80mm rodenstock lens from 6x6... no problem. That I know of I haven't noticed this problem before with the 150mm lens. Am I doing something wrong? Could it be the lens? Has anyone experienced this before? Thanks Ed Margiewicz |
#2
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one unsharp corner on prints? Help!
I'd say it's the lens. But just to be sure set up a negative and do a print
that shows the problem. Don't touch the negative and rotate the lens 90 deg in its mount. If the unsharp area moves to follow the lens rotation you've proven it's the lens (but could also be the lens mount board if you're using something like a Beseler. Curtis |
#3
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one unsharp corner on prints? Help!
Thanks Curtis and Robert I am going to try both.
Ed "Ed Margiewicz" wrote in message ... Hello, I need some help. I have been making some 8x10 prints from 4x5 slides using my 150mm rodenstock rodagon lens. For the most part my prints are full frame. I am getting one corner that is not sharp and in fact it looks like movement. It always happens in the same corner. I re-aligned my enlarger and assured my paper is laying flat. My easel is totally flat. When I change to my 135mm Nikon lens problem goes away. Prints made with my 80mm rodenstock lens from 6x6... no problem. That I know of I haven't noticed this problem before with the 150mm lens. Am I doing something wrong? Could it be the lens? Has anyone experienced this before? Thanks Ed Margiewicz |
#5
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one unsharp corner on prints? Help!
On Sat, 31 Jan 2004 11:04:07 -0800, "Ed Margiewicz"
wrote: Hello, I need some help. I have been making some 8x10 prints from 4x5 slides using my 150mm rodenstock rodagon lens. For the most part my prints are full frame. I am getting one corner that is not sharp and in fact it looks like movement. It always happens in the same corner. I re-aligned my enlarger and assured my paper is laying flat. My easel is totally flat. When I change to my 135mm Nikon lens problem goes away. Prints made with my 80mm rodenstock lens from 6x6... no problem. That I know of I haven't noticed this problem before with the 150mm lens. Am I doing something wrong? Could it be the lens? Has anyone experienced this before? Thanks Ed Margiewicz Quite likely the carrier is not centered with the lens and you are running the image outside the circle of sharpness of the lens. Remember the circle of illumination and the circle of sharpness is not the same. Most lenses lose definition when approaching the limits of thier circle of illumination. Does the corner sharpen up by much when the lens is stopped down to f/22? Possibly the lensboard has an off center lens hole in it. |
#6
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one unsharp corner on prints? Help!
I never thought the the center of the lens and slide could be out of line.
But I took my lens and lens board in hand an managed to move the lens around in the lens board hole. I found there is alot of play there. The lens thread is 50mm and the lens board hole is 52mm in diameter. This is a new beseler lens board and is supposed to be 50mm. I must have moved it around while putting it in and out of the enlarger. Thanks for your help. I am going to try your method of alignment. Ed Margiewicz "Dr. Dagor" wrote in message om... For the most part my prints are full frame. I am getting one corner that is not sharp and in fact it looks like movement. It always happens in the same corner. The importance of lens alignment dawned on me about thirty years after I started printing. The center of the neg and the center of the lens need to be aligned. They need to be on center and they need to be parallel. There are lots of methods to doing this. Among the current popular methods is to use a laser. You can make a suitable laser out of one of the cheap, small laser levels from the hardware store and a penta prism or right angle prism. Here's the method I use. 1. Level the easel and place the laser on it so the beam is straight up. (That's the hard part.) 2. Put a good, first surface mirror in the negative stage, and make sure it is parallel to the easel (no lens installed). Repeat this for the lens stage. 3. Install the lens and position the laser so the light is aimed near the center of the lens. Adjust the horizontal position of the negative stage and lens to make sure the center of the negative stage opening lines up with the center of the lens. (Laser, lens, and negative stage are co-linear.) 4. Put the mirror back in the negative stage. If everything is in alignment, the laser light should go to the negative stage and back along the same path -- even if the lens is slightly off center. It took me a while to realize this, but if the laser light hits the lens straight on, it should leave the lens straight (at least close to the center of the lens). If the laser beam hits the mirror straight, it should be returned along the same path. Hope this helps. |
#7
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one unsharp corner on prints? Help!
For the most part my prints are full frame. I am getting one corner that is
not sharp and in fact it looks like movement. It always happens in the same corner. The importance of lens alignment dawned on me about thirty years after I started printing. The center of the neg and the center of the lens need to be aligned. They need to be on center and they need to be parallel. There are lots of methods to doing this. Among the current popular methods is to use a laser. You can make a suitable laser out of one of the cheap, small laser levels from the hardware store and a penta prism or right angle prism. Here's the method I use. 1. Level the easel and place the laser on it so the beam is straight up. (That's the hard part.) 2. Put a good, first surface mirror in the negative stage, and make sure it is parallel to the easel (no lens installed). Repeat this for the lens stage. 3. Install the lens and position the laser so the light is aimed near the center of the lens. Adjust the horizontal position of the negative stage and lens to make sure the center of the negative stage opening lines up with the center of the lens. (Laser, lens, and negative stage are co-linear.) 4. Put the mirror back in the negative stage. If everything is in alignment, the laser light should go to the negative stage and back along the same path -- even if the lens is slightly off center. It took me a while to realize this, but if the laser light hits the lens straight on, it should leave the lens straight (at least close to the center of the lens). If the laser beam hits the mirror straight, it should be returned along the same path. Hope this helps. |
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