Symptoms of oily aperture blades June 20, 2010 at 1:13 pm

Oily aperture blades is one of the maladies that can effect old camera lenses. Oil gets onto the blades when the grease in the focus gearing breaks down and leaks. Age and heat are typically what causes the grease to break down i.e. a lens left in a car on a hot sunny day. The blades should be absolutely dry, they do not need lubrication.

The primary symptom of oily blades is usually over exposure on shots where aperture is set smaller than wide open. So for example with a 85mm f1.4 lens, wide open is f1.4. If you set f5.6 on the camera and take a picture it comes out overexposed for no good reason.

What is happening is that while focusing, the camera holds the lens wide open so you have a bright viewfinder and the AF unit can do its job well. When you press the shutter release the camera closes the lens to the specified aperture and takes the picture. With oil on the blades, the blades don't move or not quickly enough to get to the correct position. The result is that you end up with an aperture more open that what was specified on the camera.

There are a few ways to check and see if this has happened to a lens.

  • Visual inspection is the best way. Obviously if you can see oil, you have identified its existence. Remove the lens from the camera and shine a flash light into the lens and look down on the blades. In most cases you can get the best view looking through the front element but you can also try the rear. Oil will appear as a circle or little triangular wings. Clean blades will look consistent and dry. Patterned discoloration is generally a sure sign of oily aperture blades. In large aperture prime lenses this technique is usually very easy to do. For zoom lenses it can be very more problematic.
  • Check "snappiness" of the blades. With the lens off of the camera, pull the aperture actuator back to open the blades. It should retract smoothly without stickiness or inconsistent resistance. When released, the blades should snap closed. If they stick in place or close sluggishly, this may indicate oil on them or a broken return spring.

Some lenses will operate fairly well even with oil on the blades and in other cases the blades might become completely stuck.

The difficulty in cleaning blades varies considerably between lenses. In any case for this job you will need the right tools, instructions and care. If you decide to give it a try, take good pictures or make a video of the disassembly, so you know how to put it back together. Work over a tray or have some way to capture parts if they drop from your work or a spring fires them off.

Of course, for rare or valuable lenses please consider a reputable repair shop. I have heard good reports about Keh’s repair service

Nikon 18-200 F3.5-5.6 VR 2 Demonstration / Review July 30, 2010 at 10:25 am

Supplemental information: the VR uses quite a bit of battery. Probably as much as the flash at near full power. Also, the VR "sleep" behavior I demonstrate is true of all VR I've tested. I went to the store and tried 5 different VR lenses and they all went to sleep if you held the lens too still. This only happens when you brace yourself or rest your elbows on something. I doubt you could hold it still enough free-standing. "Normal" mode will attempt to actually lock on and hold that position where as "Active" mode simply dampens movements but does not attempt to out-right stop them. NOTE: be sure you turn off vr for any long exposure! The lens will "drift" causing any long tripod exposures to appear motion blurry. Kind of ironic.

Tamron lens sale/rebates on Amazon June 20, 2010 at 2:47 pm

Following the nice Sigma sale Amazon just had (maybe it is still going - I am not sure) Amazon has a number of Tamron lenses with discounts.

Tamron Discounts on Amazon.

Between Tamron and Sigma, I have had better luck with Tamron. The outstanding Tamron 17-50 f2.8 is one of my more heavily used lenses. For some the range is too limited, but you can't fault the image quality for the price.

Anyway, if you have been considering a Tamron lens, this might be a good opportunity to save a bit.

Nikon CLS Demonstration Video June 17, 2010 at 7:24 pm

A simple and nice example of using the Nikon flash system. One remote flash that is fired by the camera's on-board system. In macro photography like this it is important to note that the main on-board camera flash is not contributing to the exposure, it is only triggering the flash. Otherwise the on-board will cause reflections and glare that a remote flash wont.

On my Sony A700 this is a problem because you can't turn off the on-camera flash. So a trick I used was to tape a piece of exposed film over the flash. This way the signal light could still trigger the remote flash while not contributing to the overall exposure. (if you do this make sure the camera is set to wireless mode or you will melt the film to your on-camera flash... not ideal). Obviously the Nikon system is better.

A quick demonstration using Nikon's CLS with SB-800's and a Nikon D200