What's in a Zeiss lens?

[chin]

I have been using the Minolta A-mount system since taken up photography in around 2001.

I always went for the top quality lenses even though they are heavy and expensive. The logic is that if not go for the top quality lenses, why bother to use large cameras at all? Instead of using low quality super-zooms, why not just use small digicams?

Anyway the first 3 lenses I bought were all fixed focal length (means non-zooming) with very large aperture - they were 85mm/F1.4, 35mm/F1.4, and 200mm/F2.8. It was funny that almost every time when people picked up my camera, they first thing they did was trying to rotate the lens barrel to zoom, and found out there was no zoom function.

Anyway, after perhaps a year I got myself a zoom lens - the 28-70mm/F2.8. This lens had traveled with me to many places including those with extreme weather such as Tibet & Xinjiang in China and hiking in northern India. Just about all the places in Travelogues before 2009. I imagine in terms of distance traveled, it has gone around the globe a few times.

The exterior of this lens is quite beat up, with chipped paints, scratches, etc... but the optical part still works very well.

In the 3rd pictures, it shows very clearly that I do not put on any UV or protective lens in front. This is one of the most common item people put on, and all decent camera salesman would be able to sell easily. To protect your lens. I think it's nonsense to buy top quality glasses then put a cheap plastic in front.

[chin]

After Sony took over the Minolta camera business, I made a switch to the top of the line Sony body A900 after realizing that the advances in processing power did make very visible difference in picture quality. And one thing came after another, and I started to buy top quality lenses made by Sony.

This time, the first lens to buy was the 24-70mm/F2.8 made by/with Carl Zeiss. My main motivation wasn't the Zeiss name, but the desire to have a lens that can focus faster. This one has internal motor built in so the focusing is much faster and quieter than the old Minolta one. This was a very expensive lens at cost of about HK$12,500. (The price on US online retailers is around US$1,600.)

The image quality is simply stunning. And I found myself using this lens in probably 90% of my pictures. I have bought 2 other Zeiss lenses since then.

[chin]

A few months ago, I started to see some of the pictures I took were badly focused. Initially I thought I had bad hand shakes. Then I noticed that the bad focusing only happened when the aperture was wide open at 2.8. Once step down to 5.6, the image would be very sharp too.

(For my friends who are not technical savvy, Aperture = Focal Length / D, where D is the diameter of the hole inside the lens barrel. So a low aperture means the ratio is low, which in term means the D is large given a focal length, which in term means more light can come through the lens. See pictures below for illustration. Photography is basically the capture of light, and more light can possibly come in, the better.)

So a few weeks ago I took the lens to Sony for check up. They came back saying the "axle" of the lens was broken and cannot be repaired. The replacement cost would be HK$4,660 labor plus parts. That cost is more than 1/3 of the original purchase price! Seeing that I didn't have many options, I gave them the go ahead. But that's not the end of the story.

Now some pictures showing aperture at work. The pictures below shows the core of the broken lens. Compare the hole in the middle in the following three pictures. And you can see the aperture from wide open to narrowed down to a small hole. And you can see the mechanism to close the aperture is through the 9 circular interlocking blades.

[chin]

Another look at the aperture blades and the lever that controls how much to open. When the lens is put on the camera, this lever would be locked into a counter part in the camera, and allows control from the camera.

[chin]

The price to fix that lens was very high. It's high enough to buy a mid-range model with a kit lens.

I am still not convinced that the core had to be replaced, instead of fixed. In my mind, there is lingering suspicion Sony is trying to make a killing in a situation where a owner does not have much choice. And I am sure the price of fixing it has nothing to do with material and labor cost, but a magic economic or marketing research discovered highest price point where the owner is still barely willing to pay.

About two weeks ago Sony called that I could pickup the lens. But when I asked if I would be getting the broken core back, they said no. And that it was their policy not to give the parts to owner.

I then read the agreement, found the policy seems to be related to defective parts. And again argue with them that mine was not defective but damaged, otherwise they should have replaced the part for free. And I had to relate to changing tires in my car and getting the old tires back, pulling my tooth and getting the tooth back, etc...

The Sony guy's respond was that if I take the part away, I had to pay more. And then he said he will try to ask management if they can try to make an exception. I had to tell him firmly that I was not asking "if I can do that", but requesting to do so. And that if he cannot decide, have someone higher up to call me. At the end, they gave me this part and charged the same amount.

Why was I so insist on getting the broken core back? First I wasn't very happy about the cost to fix it. Second I also want to see what's inside my lens.

Now that I can see and play with the mechanism, and took pictures to show my friends, I am at least a bit less unhappy about the cost to fix it.

The following pictures shows the zoom mechanism. Compare to the above pictures and you can see the grayish part is now extended fully backward. I wonder if the very visible scratch were made during repair or from normal usage. Also why some many notes? I hope the guy who fixed this wasn't a first-timer.

[chin]

The technical specifications of this Zeiss lens says 17 elements in 13 groups. I can clearly see 2 or 3 glasses still inside the core. Does each glass count as one element? Is each moving part of the barrel counted as one element?

The largest glasses, which I think could be the most expensive components and where the Zeiss name matters, are not included in this core. I assume they were reused in the fixed lens. I can only imagine that those large glasses cost a lot and if replaced, the cost would be even higher.

The above pictures were taken with the now fixed lens. It seem focusing quite correctly. I will found out next week in my trip to Yixing.

(BTW the full name of this lens is "Carl Zeiss Vario-Sonnar T* 24-70 F2.8 ZA SSM  SAL-2470Z"    )

[kai]

Chin, I strongly agree with your action.  This is very reasonable and absolutely is your right.  I always don't believe these companies, charging unreasonably high (just like some car companies do).  At large aperture value, there is always focusing problem.  When you lower the aperture by 1-2 stops, problem will be solved.  Does your camera has the function of adjusting the focusing point?  I usually adjust it a little bit front or backward when I have such problem. 

[chin]

Chin, I strongly agree with your action.  This is very reasonable and absolutely is your right.  I always don't believe these companies, charging unreasonably high (just like some car companies do).  At large aperture value, there is always focusing problem.  When you lower the aperture by 1-2 stops, problem will be solved.  Does your camera has the function of adjusting the focusing point?  I usually adjust it a little bit front or backward when I have such problem. 

The problem was more than the usual lost of sharpness at large aperture. The image was shaky. The following picture was the one of a few that made me suspect maybe problem with the lens. At F2.8, 1/80, ISO250, I think the quality should be much better.