Accessories

What Do The Numbers Printed On Your ND Filter Tell You About The Filter?

When you are shopping for the ND filters, you may have been in a situation where the numbers (printed on the filter) confuse you more than help you. All you want to buy is 1-stop, 2-stop, 3-stop or 10-stop filter which blocks 1-stop, 2-stop, 3-stop or 10-stop of lights respectively but the numbers manufacturers use to represent the f-stop creates confusion. When I bought my first ND filter back in 2012, I actually ordered the wrong filter because of this confusion. I wanted to buy a 3-stop ND filter and when I looked online, it was showing Neutral Density 3.0 and I thought it was the right filter. But later when it arrived, it seemed darker than it should be for a 3-stop filter and after doing little bit of research, I realized that the filter I got was a 10-stop filter and not a 3-stop filter. My fault was not to do proper research before buying the item but I think it would be fair to blame the part of the mistake on how manufacturers label their product as well. Why wouldn't they simply market the filters as 1-stop, 2-stop or 3-stop filter and avoid any possible confusion? I don't know the answer for this question yet but the good news is that some of the vendors have started using more sensible naming practice with the detailed description of the products. Today, I was trying to get another ND filter and the past memory came back to me. So, I thought it would be helpful for you guys to share what I have learned so that you can make the right decision when you are shopping for the ND filter. After I made a mistake during my first purchase, I tried to find out why manufacturers use these numbers and how does this naming conventions make sense? After knowing the science behind the numbers, I shifted more blame towards me for the mistake I made but I think there is still some room left to blame the manufacturers as well. It's the manufacturers job to market their products as clearly as possible so that the buyers can easily understand what they are getting.

Let's take an example of the ND filter I was going to get today and see what the numbers tell us about the characters of the filter.

Name of the ND Filter (on Amazon) - B+W 77mm Neutral Density 0.9-8x Filter #103

In the above example, B+W is the name of the manufacturer who built the ND filter and 77mm is the diameter of the filter to fit the 77mm diameter lens. You can't fit 77mm filter on 72mm lens which is obvious. This is also something you have to be careful while shopping for the circular filter. You have to match the diameter of the filter and the lens. Now, the more confusing part of the name is 0.9-8x and #103. Let's see what do these numbers suggest.

The first number 0.9 represents the multiple of the f-stop optical density (0.3) with regard to how much light the filter is letting through the lens to the sensor. The number 0.9 in our example filter is a multiplication of (0.3) and (3) which tells us that this is a 3-stop ND filter. By using this filter, only (1/2) * (1/2) * (1/2) = 1/8th of the light that hits the front of the filter is passing through the lens. The number 1/2 would be the fraction of the lens area opening if the optical density would be 0.3 compared to the full lens opening of 1 for 0.0 optical density (which means no filters are attached to the lens).

The second number 8x suggests that if you use this filter on your lens, you will need 8 times more light than without the filter to get the same level of exposure. You can get 8 times more light by using the longer shutter speed, widening an aperture (if possible), increasing the ISO value or by using the combination of the three. How to adjust the exposure setting depends on what you are trying to achieve by using the filter. Usually, ND filters are used to get the long exposure shot and hence you would want to increase the shutter speed to compensate the loss of light with the introduction of the filter.

The Third number #103 represents the general naming convention (look at the table below) to represent the 3-stop filter. So, if you look closely, all these numbers mean the same thing and that is the filter in our example is a 3-stop ND filter. If we attach this filter in front of our lens, we need to slow down the shutter by 3-stop (or 8 times longer shutter speed is required) to get the same level of exposure as we would get without the filter. If you are shooting with the shutter speed of 1/8th of a second, an aperture of f/11 and the ISO 100, after applying a 3-stop ND filter, your new shutter speed would be 1 second (1/8 * 8 = 1) to get the same exposure considering the other two exposure parameters, aperture and ISO, are same. However, in a real world scenario, you might need to adjust the calculated shutter speed little bit up or down depending on shooting condition and the quality of the filter you are using.

If the filter in our example had a 3.0-1000x number on it, it would mean a 10-stop filter (3.0 = 0.3 * 10) letting in only 1/1000th of the light and requiring 1000 times longer shutter speed to get the same exposure as without the filter. If we do a proper math using the same formula we used before and multiply (1/2) * (1/2) *.....* (1/2) 10 times, the actual number should be 1024x but for the simplicity, 1000 is being commonly used as a rounded number. If you are interested to know how to take a long exposure shot using a ND filter, here is an article I posted earlier last week about Using a 10-Stop ND Filter for a Long Exposure Shot. You can also stack the filters and multiply the effects as well. If you use 0.9-8x filter on top of 3.0-1000x filter, the effective value would be 3.9-8000x requiring to keep the shutter open for 8000 times longer than without the filter.

During my research, I found this table below on the Wikipedia and thought it could shed some lights on the discussion we just had about the significance of the numbers to represent the ND filters. The rest of the article below is an excerpt from the Wikipedia.

In photography, ND filters are quantified by their optical density or equivalently their f-stop reduction.

ND-Filter-Numbers.jpg

Note: Hoya, B+W, Cokin use code ND2 or ND2x, etc; Lee, Tiffen use code 0.3ND, etc; Leica uses code 1x, 4x, 8x, etc.

Manfrotto 175F-1 Spring Clamp With Flash Shoe

If you are looking for something that can hold your flash unit anywhere you go, Manfrotto 175F-1 spring clamp could be your best option. This clamp is a great product and should be a part of any strobist's basic lighting kit. It provides a great amount of versatility and can be attached to a light stand or clamped into anything. The ball head socket allows you to position your flash in any position you like, allowing you to create your shot however you envision it. It takes only few seconds to clamp it onto to a piece of furniture without fear of marring a surface due to the small rubber feet built into the clamp.

Manfrotto 175F-1 spring clamp

Manfrotto 175F-1 spring clamp

It is very handy for mounting the flash units like SB-600 or SB-800 in places where you can't use the light stand. It clamps very well and it's secure. The plastic cold shoe fits the strobe nice and sung so that you don't have to worry about the strobe falling out. The clamp end is strong and grips things very well. It also has a standard light stand stud on it and a clamp as well to accept a stud from the light stand. It can hold up to 4.41 lbs and rotates 360 degree. The clamp is made up of aluminum and steel and it weighs about 0.73 lbs.

Manfrotto brand is known for the quality products. I own several products from Manfrotto like 055XPROB pro tripod, spring clamp, 498RC2 ball head. They are excellent quality products and I love them. Their build quality is extremely strong and sturdy. Their products are little expensive than what you get in a regular market (non-brand item) but worth every penny and it will pay you off in the future.

How Often Should You Clean Your Lens Or Camera Sensor?

Cleaning your camera and the lens is a very important part to take care of your equipment and it helps to produce a good quality picture consistently. Even small fingerprint on the front glass of the lens can impact on the quality of the photos. How often should you clean your lens and the camera? It all depends on how often you shoot and where do you shoot. For example, if you shoot a lot in a beach area where sands and dusts are present, you may have to clean your lens for every next shot and your camera sensor more often than people who shoot inside the studio. It’s very strange to accept the fact that lots of photographers who own an expensive lenses and camera body never pay an attention on cleaning their tools which help them capturing stunning photographs. If we take good care of equipment, our equipment takes care of us. Personally, I clean up my equipment every time I come back from the shooting and before storing it to dry cabinet. It is also very common for photographers to use an UV filter in front of their lens so that the actual lens won’t get accidental scratch and they don’t have to clean their lens every time and just cleaning an UV filter will do the job.

Lens cleaning kit

Lens cleaning kit

You can use a microfiber towel to clean the lens body and the front glass which doesn’t leave a residue on the surface. Don’t try to clean your lens or camera sensor with a rough surface material like normal towel or napkin paper; you may permanently scratch the front glass of the lens if you use hard surface material. I don’t recommend cleaning your sensor unless it is covered with the dusts and you are experiencing a problem with the image quality. Cleaning image sensor by yourself without having proper knowledge may destroy your camera permanently. Some DSLRs (Nikon D90 for example) come with an option that will lock the camera mirror up and allows you to clean the sensor using a blower or other cleaning tool provided by the camera manufacturer or the other individual company who produces quality accessories for DSLR.

If you go to the SETUP MENU by using the MENU button on the back of your D90 or other model DSLR, you will see an option called “Lock mirror up for cleaning” which is specifically designed for the photographers to clean up the sensor if in case there is a dust. You can use this option to raise the mirror up and open the shutter so that you will have access to the sensor for cleaning with a blower, brush, or swab as shown in the picture above. You can find those lens cleaning kit online for $20 or less. Nikon D90 allows you to use this feature only when your camera has a fully charged battery or sufficient battery for the cleanup because you don’t want the camera power to fail while you are still cleaning your sensor.