Hi there,

Unfortunately I let my Rokkor fell on the floor, now wothout trying to save it putting my left foot to prevent it to hit the floor direclty. I partially succeeded but this happened.

Sure, if he has the right tool to do it and you feel the need to use filters, then go for it. I purchased a filter ring dent repair tool (reverse vice) a few months ago. Even with this special tool, a great deal of care needs to be taken in order not to do more damage. If you were local, I'd offer to do it for you, as I have figured out some of the tricks to doing it right.

Ouch!

I'd check for decentering . . . is the lens equally sharp in all quadrants of the frame at infinity and close focus?

Certainly check for decentering, but I would be very surprised if you find any. The lens design has no floating elements, no internal focusing, etc. Just elements solidly in place, with very little room for movement, if any. Damage serious enough to cause decentering in such a lens would likely also result in a deformed, stiff helicoid or some other major external damage. Also, ironically, the best copy of this lens that I have ever used (and still own) has filter ring damage (repaired).

Will do some tests and post here. Thank you all!

A plier and some muscle work should do it Go for it!

Oh... doesn't that just break your heart.
Ouch indeed.

I hope that lens still performs as it should.

Here it goes:

Min. focusing distance @ f/2 or 2.8, 1/100ish:

cogitech wrote:
Sure, if he has the right tool to do it and you feel the need to use filters, then go for it. I purchased a filter ring dent repair tool (reverse vice) a few months ago.

Paul, where'd you buy this? I have two of this exact lens with similar damage (not quite as bad) I was going to try hammering-out with a curved piece of wood, but I'd rather do it right.

I've had dented filter rings with many of my lenses. Repairing is simple but takes a long time as you don't want to ruin the filter thread. Yesterday I used the soft plastic back end of my pliers and gently and carefully hit the bent part of the ring back into place. Much patience is needed as it takes frustratingly long to achieve this.

When the ring is rougly in place, check if the filter thread is still smooth. If not, visit your local hardware store for a specialised tool (in Dutch its called a "tap" if that helps) to carve it out. The last part is to put on a filter, this forces the ring back in place, but it's essential that the filter remains straight here or you'll damage the filter thread.

A long explanation for a rather easy procedure. For extra safety you could protect the ring with a towel, however it makes it harder to see what you are doing.

good luck

Cableaddict wrote:
cogitech wrote:
Sure, if he has the right tool to do it and you feel the need to use filters, then go for it. I purchased a filter ring dent repair tool (reverse vice) a few months ago.

Paul, where'd you buy this? I have two of this exact lens with similar damage (not quite as bad) I was going to try hammering-out with a curved piece of wood, but I'd rather do it right.

I got mine off e-bay from a seller in India.

The trouble with these tools is that they have the potential to create a reverse dent (stretch) on the opposite side of the ring, so much care needs to be taken. The curved wood method that I have seen actually seems a bit safer in this respect, but I was able to fix several filter rings, very very carefully, with this $50 reverse vice tool.

hubsand, Paul, anything to say about the test crops I put here?
TIA

I agree that the book shot could be a DOF thing. Even the slightest angle could put the books out of focus in that part of the frame.

Unless you notice it being consistently softer on one side than the other, over multiple aperture settings and focusing distance (which you are not, based on the samples here), I say don't fret about it.

Paul & Biotar,

If one were to attept this repair with a tool such as a reversed whatever, or a tap, how do you first determine what the threading is? If you go in there with something that's close, but not right, you'll destroy the lens.

Do all lenses use some standard, international threading? Hmm, I guess they must, or there would not be standardized filters. Never thought about it before.. OK, never mind......

If you want to check for decentering go out one clear night and take some shots of the stars. Then compare the corner images, they should be reasonably similar in all 4 corners.

.75mm thread pitch is the standard for filters I think.

I had this issue once with a dropped CANON serenar.

The filter diameter was 52mm. I took an el-cheapo 49mm filter, nocked the glass out of it then placed the threaded part of it onto the dented part of the filter threads on the lens, took a plier and gently pushed the threads back out. I basically used the glass-less filter to make sure I did not damage the lens threads.
It got close enough. I then put silicone lube (very lightly onto a 52mm filter and threaded it onto the lens, going back and forth until it would screw in all the way fairly easily. It worked well enough to be usable.

dasrocket,

that's quite clever. I think I'll try it.

just be patient...