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Author Topic: minor scratches on rodenstock sironar digital 55mm's glass  (Read 1324 times)
studio347
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« on: November 29, 2012, 01:11:37 PM »
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Hi,
I need some advices from 4 by 5 lens' experts.
I just got an used rodenstock sironar digital 55mm lens, (which I intend to use with P65, sinar 4 by5 camera for wide angle still-life shootings @f 8 or f11) and noticed very thin & short coating scratches on the rear glass center area. such scratches you can expect/ guess when cleaned/ wiped carelessly while some dust still on the glass...
I can see that this lens was kept without the rear lens cap.
They are very thin and short. I can noticed only with LED loupe at the right angle. It's not possible to see the scratches without the loupe. But still they are located in the center area of the rear glass.
I know it's relative. But how much should I worry about the scratches for the image quality? I bought it with a good price. Should I return the lens?
Or the minor coating scratches doesn't  affect the quality much?
Let me hear some advices from you guys?
Thanks!
« Last Edit: November 29, 2012, 01:37:01 PM by studio347 » Logged
theguywitha645d
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« Reply #1 on: November 29, 2012, 02:45:15 PM »
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Perhaps they are just cleaning marks--dust really does not scratch glass. Why not try to clean it?

If you are having a hard time seeing these, then you don't need to worry.
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studio347
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« Reply #2 on: November 29, 2012, 03:02:59 PM »
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after thorough cleaning, there are still the scratches... very thin, but still there.
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Rand47
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« Reply #3 on: November 30, 2012, 07:17:40 PM »
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Hi,
I need some advices from 4 by 5 lens' experts.
I just got an used rodenstock sironar digital 55mm lens, (which I intend to use with P65, sinar 4 by5 camera for wide angle still-life shootings @f 8 or f11) and noticed very thin & short coating scratches on the rear glass center area. such scratches you can expect/ guess when cleaned/ wiped carelessly while some dust still on the glass...
I can see that this lens was kept without the rear lens cap.
They are very thin and short. I can noticed only with LED loupe at the right angle. It's not possible to see the scratches without the loupe. But still they are located in the center area of the rear glass.
I know it's relative. But how much should I worry about the scratches for the image quality? I bought it with a good price. Should I return the lens?
Or the minor coating scratches doesn't  affect the quality much?
Let me hear some advices from you guys?
Thanks!

Check this out:  http://www.lensrentals.com/blog/2008/10/front-element-scratches

Rand
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BarbaraArmstrong
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« Reply #4 on: November 30, 2012, 09:59:15 PM »
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I was told recently, by a salesman who I felt would know and who wasn't influencing a decision on my part (I was looking at new lenses) that scratches on a rear lens element are much more important than scratches on a front element.  So I thought I would see some mention in this thread of that distinction.  Is that not the case? --Barbara
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ErikKaffehr
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« Reply #5 on: November 30, 2012, 10:37:29 PM »
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Hi,

It may depend on the lens and the scratches. A small scratch on the front lens may pick up light outside the frame and cause visible artifacts.

A significant scratch on a rear element that is close to the sensor could cause a visible disturbance. The rear lens is usually smaller so scratches may cover a larger relative area.

My guess is that small scratches that are hardly visible would probably not cause any problem.

Best regards
Erik

I was told recently, by a salesman who I felt would know and who wasn't influencing a decision on my part (I was looking at new lenses) that scratches on a rear lens element are much more important than scratches on a front element.  So I thought I would see some mention in this thread of that distinction.  Is that not the case? --Barbara
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FredBGG
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« Reply #6 on: November 30, 2012, 10:44:25 PM »
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Scratches are going to affect the image quality. If they were not a problem lenses would not be as polished and multi coated as they are.

The position of the scratches can make things worse.

In your case they are at the center of the rear element.

This presents two problems. First the scratch is close to the film or sensor. More likely to project problems in the image.

Second because the scratch is in the center it will be progressively more problematic as you atop down. This is because when you are wide open\
the scratch covers a smaller area of the glass used in projecting the image. When you stop all the way down you are only using the center of the less... less glass just as much scratch... so to speak.

While a rear element scratch is closer to the film it is surrounded by dark so less likely to pick up light from the sides compared to a front element scratch.

If you are looking for sharpness and good contrast stay away from scratches
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studio347
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« Reply #7 on: December 01, 2012, 10:38:09 AM »
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Thanks for the reply!
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schrodingerscat
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« Reply #8 on: December 08, 2012, 05:33:44 PM »
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Rear element scratches usually have a more noticeable effect than the front. The impact with either becomes more apparent the smaller you stop down and how on-axis you are with the light source. All this depends on the severity of the damage and the location.

There are businesses that will re-polish and coat lenses, not sure just who does it these days. To retain the best optical performance, it would be advisable to send it to the manufacturer to have the rear element replaced.
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