How does aperture blades work

And why important? Skip to content Aperture blades sit inside the lens and are small pieces of fabric that move to reduce the size of the area that lets light pass on to the senor or film in the camera. In the picture below, you san see how the blades form a small circle: On many lenses you can actually manually move the aperture ring back and forth and see how the size of the aperture changes. Related reading What is aperture? What is lens vignetting? What is bokeh? What is OOF? What is diffraction?

Share this:. Like this: Like Loading Leave a Reply Cancel reply. How the specific lens bends the light internally seems to have some impact on the final result as well. I did hear that 7 blades gives nice star shaped lights, so that might be something to consider as well, when selecting a lens.

Number of blades is only one of the factors affecting bekoh. I have one question. I just bought componon 35 mm f4, but with no functional blades. Are there any blades from other lens which are compatible with componon 35 mm blades?

Thank you grammar guy — that one always bugs me, too. Skip to content. Background for Beginners You probably already know that the aperture of your lens affects depth of field. Different Apertures in Lenses Some lenses have only 5 or 6 blades on the aperture, and other lenses may have 9 or even 14 blades on the aperture. The lens on the right with more blades, which are rounded, is generally preferred among photographers. Quick Links. Follow us on social.

An example of this is discovering in the middle of a shoot that your lens has sticky or stuck aperture blades. Sticky aperture blades usually occur when the blades become oily.

Oily blades cause the iris diaphragm to close too slowly, resulting in overexposed photos. In bad cases the aperture blades can get completely stuck and can not stop down at all.

Usually when this happens, the blades are stuck wide open. Stuck aperture blades are not only caused by oily blades, but also by mechanical problems in the lens. In this article I will explain the possible causes of sticky and stuck aperture blades, how you can identify the cause, and how you can fix and prevent the problem. I will also take you through the step-by-step process of cleaning oily aperture blades.

For this I will clean the blades on a Minolta 50mm F1. Before showing you how to clean oily aperture blades, I will first give more information on the problem and answer some frequently asked questions:. The goal of a diaphragm in a camera lens is to block all light, except for the light that travels through the hole in its center.

This hole is called the aperture. Most modern camera lenses have an adjustable diaphragm, which is able to change the size of the aperture. It gets referred to as an iris diaphragm or iris , because of its similarity to the iris of an eye. In this analogy, the aperture can be thought of as the pupil of the eye. The iris diaphragm uses movable blades to change the aperture size. These blades are also known as aperture blades. The aperture blades can stop working properly due to a variety of reasons.

In this article I will help you fix them. There are a variety of reasons why aperture blades can get sticky, or even completely stuck. These are the most common ones:. The most common cause of sticky aperture blades is oil on the blades.

This happens when the grease on the focusing helicoid breaks down, either due to age, or due to exposure to high temperatures. The solid and liquid components of the grease separate, and the liquid oil component makes its way to the aperture blades and causes them to stick together.

This is usually a slow gradual process caused by the natural degradation of the grease. However, because lubricants generally have a lower viscosity at higher temperatures, regular exposure to high temperatures can accelerate the degradation. Aside from frequent exposure to high temperatures, a one-time exposure to extreme temperatures might also be sufficient to cause the grease to separate. The oil can flow or evaporate onto the aperture blades, but it can also end up on the glass elements or other internal components or the lens.

Some lenses are more prone to this than others. I am sure that Canon and Nikon have their own troublemakers as well. Only of those factors is controllable by the user of the lens, so it makes sense that this problem can be hard to prevent for some lenses.

It is important to note that oil on the aperture blades is not necessarily a problem. Up to a certain point, the blades will work fine with oil on them, even though it is not ideal.

In these situations you will need to address the problem and clean the aperture blades and other lens components affected by the oil. A less common reason for sticky or stuck aperture blades is physical damage to the aperture mechanism. Examples of this are bent or damaged aperture blades, or damage to the aperture linkage. These problems are usually caused by a sudden shock to the lens, or by improperly handling it in some other way. If the lens has always been in your possession, you would obviously know if your lens has been improperly repaired.

However, if you bought your lens second-hand it is possible that the previous owner did not mention this to you. Repairing damage to the aperture mechanism is possible, but it is likely that you will need some replacement parts. More on this further down the page. The return spring is a spring that snaps the diaphragm back to its smallest aperture after the control lever has been released. It is possible that a shock to the lens disconnects the spring from its mounting points, or that the spring wears out over time.

The spring wearing out due to fatigue is fairly unlikely though, as the stress during normal operation on it is small, and the springs are expected to last a long time. Therefore, any problems with the spring are most likely due to it disconnecting. In the next section I will explain how to tell these two issues, and other possible causes for sticky aperture blades, apart.

Sometimes the aperture blades do not operate properly because the camera has problems sending the correct signal to the lens, or the lens reports back incorrect data about its position. This is often caused by faulty or dirty electrical contacts on either the lens, the camera body, or both. Naturally this only applies to lenses that have the aperture electronically controlled by the camera, and not lenses with manual aperture rings as the only means of controlling the diaphragm.

All right, so you know that your camera lens has problems with the aperture blades, but how can you tell what exactly is causing it? Luckily, all possible causes have different symptoms. I will lay them all out below, so that you can identify the cause and take the necessary steps to repair the lens. If you are still able to close the diaphragm, you can shine a light into the front and back of the lens, and check if there is any oil on the surface of the aperture blades.

It is a concern if you see a significant quantity of oil however. To check whether the oil is actually causing problems, you can use the aperture control lever on the rear of the lens assuming that your lens has one.

Actuate the lever to open the diaphragm, and then swiftly release it. When you actuate the control lever, you should be able to easily move it and only feel some spring resistance. If the diaphragm does not close or move at all but the control lever still has its natural springy movement , then this might be caused by excessive oil on the blades. However, it is also possible that the blades are stuck due to one of the other causes below.

Just like when checking for slow aperture blades caused by oil, the easiest way to identify a damaged aperture mechanism or other mechanical issues is by using the aperture control lever. In both these cases you might need to open up the lens and investigate further to see what is broken or out of place. If you are able to open and close the diaphragm by moving the aperture lever, but the lever stays in place once you release it, then it is likely that the return spring is disconnected from one or both of its mounting points.

A worn out spring is not likely to occur, and usually when dealing with slowly closing aperture blades the problem is caused by oil. However, if there is no oil visible, and the aperture mechanism has no problems either, then the return spring is the likely culprit.

Identifying faulty electrical contacts is fairly easy. The clearest indicator of improperly working electrical contacts that the iris diaphragm operates correctly when the lens is removed from the camera body, but has issues when the lens is operated and controlled by the camera. To check whether the lens or the camera is causing the problems, you can try the lens on a different camera, or different lenses on the same camera.

You can also visually inspect the lens and camera for faulty or dirty electrical contacts. Damaged contacts or contacts with dirt or corrosion on them can cause problems with the signal, and need to be either repaired or cleaned.