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Forum: Pentax SLR Lens Discussion 12-01-2008, 04:48 AM  
Dismantling a lens - easy?
Posted By richard64
Replies: 24
Views: 9,840
Before you start, get the right tools! It will make it a lot easier and you'll be less likely to lose something or do any damage. Also, take lots of photos as you work. Firstly, it means that you'll be able to provide a tutorial () and secondly, you'll have them as a reference when you reassemble the lens.

It's best to get some latex gloves, you can get a big bag of them cheap from a hardware store. Wearing gloves means that you don't get finger prints on the lenses. To unscrew the name plate I found that the best thing was an M42 rear cap covered in a latex glove. This means that the latex covered rim of the cap is in contact with the name plate and the front element is not touched. The name plate screws into the filter ring, so if there is a dent in the filter ring you have to do something about that first. You may find it useful to clean the filtyer ring with a toothbrush or a stiff artists paint brush first. This will clean out any crud in the threads and make unscrewing the name plate easier.

The name plate can be stiff. Recently I took apart an almost mint Super Takumar (it was unused except for the fungus that I needed to remove) and it took quite a bit of force to get the name plate to move (I guess it had not been moved in 40 years). So it is important not to use a method that could mean touching the front element.



The screws are very small, so be very careful not to lose them. They are also a real pain to get back into place and there are various techniques people employ - magnetic screw drivers, a bit of grease on the screw head etc. I used tweezers and carefully pushed the screw in place.

I don't know what the M50/2 is like inside. The Super Tak I cleaned was a 28mm and the front group was screwed in. (On my M50/1.4 it appears that there is a ring that secures the front element.) The fungus I wanted to remove was in the front group, so I unscrewed it, and made sure that the rest of the lens was covered to keep out dust.

To disassemble the front group I had to unscrew a ring. This one had indents in it. If you see a ring like this, you should use a lens spanner wrench to unscrew it. That is the safest way. Unfortunately spanner wrenches are $20 or $30 so you are now talking about a specialist investment. You can use a screw driver in the indent, but since you will have to use some force, you do risk the screw driver slipping and scratching something. To mitigate this risk I put a micro-fiber lens cloth over the lens and then put my thumb on the lens near where the screw driver will be - if I was going to scratch something it would be my thumb! In fact. holding it like this, the force is away from the lens surface. However, in my case, the couple of times the screw driver slipped it scratched the edge of the lens. With a wide angle lens the edges of the elements are painted black, so I had to do some touching up later with a sharpie. I don't think you'll have that problem with a 50. As I said, if you get a spanner wrench you'll save yourself that problem. If you use screw drivers you will also scratch the ring. Remember that flare is caused by reflections inside the lens, so when you have reassembled the lens use a black sharpie (or a fine tipped fiber tipped pen) to remove the scratches. Be careful not to get the ink on the lens surface, but you do not want any shiny scratches inside the lens.

Once I had taken the group apart I got access to the fungus. Now the fun begins. Make sure that any element that you remove you keep in a clean place, on a pec pad (and covered) and that you know which way up it goes. I put a sheet of A4 white paper on my desk away from where I am working and put on it the pieces in the order I remove them, each one face up. I also use rear end caps to hold any screws I remove.

Search the internet for advice on what to use to clean off the fungus. Different people recommend different cleaning agents. I used denatured alcohol (90% ethanol, 10% methanol), it worked fine for me, but you have to decide what is best for you. The lens coasting is quite robust, but you do not want to scratch it with anything, so use clean lens cloths. Patience is important. I used a pec pad to apply the liquid, and then gently rubbed it off with a dry pec pad. It took me about 20 minutes to remove all the fungus. (I looked obliquely across the lens surface to check.) After that, I reassembled the lens, blowing it frequently with my rocket blower.

So here's what you need to get:

- good jeweller's screwdrivers
- fine pointed tweezers
- latex gloves
- spanner wrench
- magnet, just in case you drop a screw on the floor
- lens cloths, micro fiber, pec pads.
- cleaning fluid
- toothbrush

You'll find that there is a lot of advice on the forum.manualfocus.org forum.

As always, let us know how you do, and if possible post some before, during and after photos.

Richard
Forum: Pentax SLR Lens Discussion 03-11-2009, 06:47 AM  
Industar 50-2
Posted By richard64
Replies: 7
Views: 16,080
After looking at some photos on this forum and on others I thought I would give this lens a try. At 15 this is a cheap lens and mine is in good condition. The first thing I did was to sort out a hood. The I-50 has a 35mm filter thread and I have no suitable hoods. So I got a Gu pot (Gu are rather indulgent chocolate desserts). I chopped off the bottom, and then used a craft knife to pare it down until I could push it over the filter ring. Then I used some sandpaper to roughen the inside to a matt finish.

Here's the lens and hood, separately and then with the hood on the lens.




Yes it does look weird, but since the lens is not coated I wanted to reduce any flare. One issue with this lens is that the filter ring is also the aperture ring, but with my hood in place the "aperture ring" is much wider and easier to use. Unfortunately there are no clicks on the aperture ring and the lens is fully manual, so if you focus wide open you cannot accurately stop down to a particular value. Also, it is possible when you stop down to turn the focus ring too. So it can get a little fiddly to focus and get the best aperture.

Why use a 50mm f3.5? Well, I found that for landscape it was a bit ordinary, and similarly for closer focus images (65cm is the closest focus). I found that the lens handled greens very well, and blues were really quite vivid. The photos I had seen elsewhere were with extension tubes, and this is what I wanted to try. I tried 8, 10 and 22mm and decided that the images from last two were the best. The following were with the 22mm tube, no flash, handheld and at about f5.6-f8.



It is spring time, and the only insects about are flies sunning themselves.



This is a magnolia bud just opening. I also took some pictures at f3.5 where the DOF is very small, but interestingly, the hairs are still visible, so even wide open this is a sharp lens.

This is an interesting lens for macro work, and for the price it is worth giving it a try.

Richard
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