Wratten filter for slit lamp

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12 filter

When your lens starts to become less flexible and lose its focusing ability, you’ll start to have trouble focusing on things close-up. Presbyopia is essentially farsightedness (hyperopia) that happens with aging. You might find yourself holding reading materials farther away from you to read. Or you might just notice that your eyes get tired from reading or doing close work more easily than they used to.

Kodak Wratten filters PDF

The eye lens absorbs, focuses and directs incoming light to the retina, the light-sensitive tissue in the back of your eye. It changes its shape automatically to focus on objects at different distances. It can make itself flatter or rounder to bend incoming light from different distances toward a single point. This is how it fine-tunes your focus. The lens provides about 30% of your eye’s focus; your cornea provides the other 70%.

Your eye lens is the last membrane that light passes through before reaching your retina. It’s your eye’s chance to fine-tune your focus. Made up of clear, crystallin proteins, your eye lens flexes and changes its shape to bend the incoming light toward your retina. It’s a powerful design, but it does start to wear out as you get older.

If you would like to read more about filters, check out my post Shopper’s Guide to Camera Filters over on my car photography website/blog.

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What is a Wratten filter

The lens of the eye sits just behind your pupil, which is the dark spot in the middle of your iris, the colored part of your eye. The pupil is an opening that lets light into your eye. The iris controls the size of the opening and the amount of light coming in. Light passes through your pupil to the eye lens, which focuses it onto the retina behind it. This makes your eye lens the second-to-last layer in your eye.

One of the most popular filters for shooting infrared is the Wratten 89B and it’s one of the three filters in my basic IR kit. One filter that gets used is Cokin’s Infrared 89B filter and instead of placing the filter in a Cokin holder, I typically hold the filter against the front of the lens to avoid daylight coming in from the sides and polluting the IR. The other two filters in my kit are a 58mm Hoya R72 and a 58mm Singh Ray iRay filter,* both of which I use with step-up/down rings on my mirrorless cameras. Kodak’s 3×3-inch 89B Opaque Infrared (IR) Optical Wratten filter is selling for $114.95 as I write this. And while I own a lot of 3×3 gel filters, I don’t have that one.

My book, The Complete Guide to Digital Infrared Photography is available new for $30.82 with used copies stating at around twelve bucks from Amazon as I write this. Creative Digital Monochrome Effects has a chapter on IR photography and is available from Amazon for $19.30 with used copies starting around $2.00, a bargain I think.

Wratten

Sometimes colored on-camera filters are referred to by their Wratten numbers. The English firm of Wratten & Wainwright introduced the Wratten system in their 1909 book The Photography Of Coloured Objects. Established in the 1877, the company primarily made photographic plates and chemicals and in the 1880s and ’90s started producing cameras. In 1912 George Eastman acquired Wratten & Wainwright and their name, for filters anyway, stuck.

*Update: When I purchased my 58mm Singh Ray iRay filter there as only one option. Now there are two: The 830 (Standard) I-Ray produces the dramatic black & white look of pure infrared and the 690 (Custom) I-Ray, produces both black & white or “near IR” color, which is especially useful for the blue sky” effect.

Surgeons can also replace your eye lens with an IOL before you develop a cataract to correct refractive errors like myopia, hyperopia or presbyopia. In this case, it’s called refractive lens exchange.

While age-related wear and tear on your eye lenses is inevitable, taking care of your eyes can help delay the process and minimize the damage. That means protecting your eyes from UV rays with sunglasses and avoiding environmental pollutants as much as possible, particularly smoking and secondhand smoke. Having diabetes can increase your risk of cataracts. Managing it well can help reduce that risk.

Cataract surgery is the only treatment for cataracts. During this common procedure, a surgeon removes your clouded eye lens and replaces it with a new, artificial lens (intraocular lens, or IOL).

Cataracts (cloudy spots on your eye lens) make your vision blurry or foggy. You might feel like you’re viewing the world through a dirty window. They often start in one spot and then spread. From the outside, they make your pupil, the dark spot in your eye, look cloudy, more like gray or white than black. (Babies can be born with cataracts related to genetic disorders, and this is one way to recognize them.)

Wratten filter optometry

How I made this shot: Who says all infrared shots have to be in monochrome? Not me. The above image was captured as a RAW file using a Canon EOS 50D with an old Russian-made Zenitar 16mm f/2.8 Fisheye lens shot using hyperfocal distance focusing. Exposure was 1/400 sec at f/16 and ISO 400. The color effect was created using the “Blue Sky” technique that I showed how to create in a previous post. The interesting aspect of this technique is that, depending on the original file, other colors can creep into the shot as was the case here. Call it serendipity.

Unless otherwise noted, all of the photographs that appear on this website and its blog are copyright Joe Farace and may not be used without prior written permission of the photographer. If you would like to use any of the images that appear on these pages or license them for commercial use, please contact me at joefarace@gmail.com

Wratten meaning

Your eye care specialist can walk you through the different options and which ones might work best for you. You might benefit from different treatments over time, as aging continues to affect your vision.

Aging and environmental factors like sunlight eventually take their toll on your eye lens, particularly the older crystallin cells in the center. When these cells start to break down, they lose some of their transparency and become cloudy. This is what age-related cataracts are. As eye lenses age, they also become less flexible and less able to change shape to focus on objects close-up. This is what age-related presbyopia is.

Wratten filter optometry buy

Wratten filter chart

The lens of your eye is a unique structure that’s crucial for seeing clearly. Over time, the cells in your eye lens can start to wear out and lose some of their focusing ability. You might notice your vision becoming cloudy or your focus becoming strained as you age. Regular eye health checkups can help you keep track of the wear and tear on your eye lens. Your provider can offer treatments to help recover your vision.

The eye lens is wrapped in a transparent, elastic capsule. Small, elastic fibers called zonules suspend the lens from the ciliary body above and below it. The ciliary body is a muscular membrane that sits behind your iris. Ciliary muscles help adjust the shape of the lens. When they contract, the zonules actually relax, allowing the lens to become rounder. This is how you focus on something close up.

The lens of your eye is made up of structural proteins called crystallins. This is why it’s sometimes called the “crystalline lens.” It has the highest concentration of proteins of almost any tissue in your body. These specialized proteins give the lens its transparency and focusing power. Mature crystallins have no nucleus or organelles — they lose them as they mature. This adds to their clarity and transparency.

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The lens of the eye is similar to the lens of a camera. It’s the part that focuses and transmits light to the back, where sensors convert it into visual data. The lens is a clear, curved structure that’s embedded deep within your eye (or camera). It absorbs light and bends it to converge at a single point behind it. This focuses the light for the sensors at the back — whether that’s camera film, digital sensors or, in your eye, the retina.

When shooting infrared with filters, I often use the 89B, especially in Cokin’s A-series (67 x 71mm) size that works with most digital SLRs and mirrorless cameras. Purists will recognize that the 89B filter only permits 50% transmission of IR light at 720nm while others, such as B+W’s IR Dark Red 092 ($99.95 in 58mm) filter, passes 90% of IR radiation from 730-2000nm. For more about nanometers and how that effects IR transmission, please read my post Infrared Camera Conversions: What’s the Best Option?

But having no nucleus or organelles also prevents the cells from reproducing. This means they don’t “turn over,” as most of your body’s cells do. The cells arrange themselves in concentric layers, like tree rings. Throughout your life, new cells continue to grow at the outer edges of the circle, while the older cells compress toward the center. Eventually, the older cells at the center begin to show wear and tear.

I’ve found that Life Pixel does a great job with IR conversions and they have done most of the conversions for my Canon DSLRs and all of my Panasonic Lumix G-series cameras. This is not a paid or sponsored endorsement, just my experience.