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Author Topic: NEED ADVICE ABOUT LENS REPAIR  (Read 494 times)

drewharty

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NEED ADVICE ABOUT LENS REPAIR
« on: August 09, 2019, 09:25:59 am »

Hello,

I recently purchased a Rodenstock HR 100 to replace my Sironar Digital 105. The HR 100 was in a Sinar DB shutter, so I had SK Grimes put new F/stop scales on a Copal 0 shutter and mount the lens. I tested the resolution performance of the HR 100 at F4, F5.6, F8, F11, and F16 and was surprise by the loss of sharpness between F4 and F5.6. The reason I purchased the HR 100 was because of its reputed sharpness at F4.

The Service Manager at Rodenstock said HR lens can be adjusted on a MTF machine for a cost of approximately $450 USD, but he gave no indication whether the loss of sharpness that can be seen in the lens test between F5.6 and F4 is within normal accepted performance for the lens. My HR 40 and HR 70 do not show the same degree resolution loss between F8 and F5.6, though there is some loss of resolution.

Does the loss of sharpness between F5.6 and F4 on the attached file look normal to any of you working with Rodenstock HR F4 lens?
Has anyone sent HR lens to Rodenstock for adjustment, and did you see an improvement if the Len's performance?


Thanks, Drew Harty

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ben730

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Re: NEED ADVICE ABOUT LENS REPAIR
« Reply #1 on: August 12, 2019, 08:06:32 am »

Hi Drew
I don't know the HR 100. But I use the HR 23, 28, 32 + 90 and your attached file looks normal for me.

Regards,
Ben

BFD

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Re: NEED ADVICE ABOUT LENS REPAIR
« Reply #2 on: August 24, 2019, 07:44:56 pm »

Not to insult anyone, but I'm assuming you did multiple captures at f4 with the same result and not just one that could have been the subject of human introduced vibration?
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drewharty

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Re: NEED ADVICE ABOUT LENS REPAIR
« Reply #3 on: August 28, 2019, 10:17:25 pm »

Good question. I'm not insulted. Yes, I do take multiple series or exposures refocusing the camera each time. What surprises every time I test lens is how difficult it can be to get accurate focus wide open, even using a live view back at 100 - 150% with a good loupe. Inevitably one exposure wide open is less sharper than the others.

I decided to send the HR 100 into Rodenstock after comparing it with my HR 40, which was clearly sharper at every F stop.

I will see how much a Rodentstock tech can improve the sharpness using an MTF machine.
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BFD

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Re: NEED ADVICE ABOUT LENS REPAIR
« Reply #4 on: August 28, 2019, 10:24:57 pm »

Good question. I'm not insulted. Yes, I do take multiple series or exposures refocusing the camera each time. What surprises every time I test lens is how difficult it can be to get accurate focus wide open, even using a live view back at 100 - 150% with a good loupe. Inevitably one exposure wide open is less sharper than the others.

I decided to send the HR 100 into Rodenstock after comparing it with my HR 40, which was clearly sharper at every F stop.

I will see how much a Rodentstock tech can improve the sharpness using an MTF machine.
Would love to see what they find if you can post the verdict when you get the lens back.
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