Drop-In Filters

What Are They and How Do They Work?

My first experience with drop-in filters came while researching the Nikkor Z 800mm f/6.3 telephoto prime lens. As a premium lens that neither my photography friends nor I had seen in person, I was intrigued by its potential for wildlife photography. But I had an additional goal in mind: using it for astronomy—especially for the solar eclipse that was going to occur in April 2024.

If you’ve ever wanted to photograph the sun with anything but a wide-angle lens, you’ll know that you need a solar filter to do so safely. Just like your eye, the concentrated sun can destroy your camera’s sensor. The only exception is during the brief period of totality in a solar eclipse when the filter can be removed to capture those awe-inspiring moments like the diamond ring effect and Baily’s beads. I planned to travel to Arkansas to photograph the eclipse, and if I was going to use the 800mm lens, I needed to ensure I could find a compatible solar filter.

The Drop-In Filter Mystery

Unlike most lenses, which have threaded fronts where filters can be easily screwed on, the 800mm Nikkor doesn’t follow this standard design. Instead, the marketing materials and reviews mentioned a 46mm drop-in filter, but there were no clear explanations or visuals showing what it was or how it worked. Reviewers would casually mention the drop-in filter but never offer much insight, which left me uncertain about how it functioned.

Since this was an expensive investment, I needed to be sure I could get a solar filter that worked with it. Unfortunately, my local camera store couldn’t help either. They wouldn’t open the box unless I was ready to purchase, and they didn’t have any display or rental units. In retrospect, I should have just asked them about it, but my hubris probably kept me from thinking of it at the time.

Searching for Solutions

I started researching the drop-in filter options for this lens. Two main products came up:

1. The Nikon Slip-In Circular Polarizing Filter for $513, which is a non-interchangeable polarizing filter.

2. The Kase Tele Drop-In Filter Kit for $400, which also seemed like a permanent fixture with no interchangeable parts aside from the geared filters provided.

Both options were pricey, and neither seemed to offer the flexibility I needed for solar photography. I was starting to think I might be out of luck. Still, I decided to go ahead and purchase the lens, knowing it would be great for wildlife. If the drop-in filter situation didn’t work out, I figured I could either use a less powerful lens like the Nikkor Z 100-400mm or rig a telescope filter to the front of it like the Helios Glass Telescope Solar Filter by Seymour Solar.

Understanding Drop-In Filters

Once I had the lens in hand, I finally understood what a drop-in filter actually is. It’s essentially a filter caddy that slides into the back of the lens. The caddy itself has threads, similar to the front of a standard lens, meaning you can screw in any standard 46mm screw-in filter and use it with the lens. With that knowledge, I ordered the Tiffen 46mm 18-stop solar filter, and it worked perfectly.

I was surprised that no one in the photography community seemed to take the time to explain this. Maybe it was obvious to them, but for someone new to drop-in filters, it wasn’t immediately clear, especially since I saw those two premade filter options, which didn’t help much with my confusion.

The Problem with Replacements

While researching this, I noticed questions in online forums from people looking for replacement drop-in filters for their lenses. Since the caddy is made of plastic and feels somewhat flimsy, it makes sense that people would want spares. Having a second caddy could also allow for quicker filter swaps, which is particularly useful during solar photography when you need to remove the filter quickly at the start of totality and replace it immediately afterward.

However, when I searched for replacements, I couldn’t find anything listed as an accessory for the 800mm lens. It was almost as if replacements didn’t exist. That’s when I dug a little deeper and found the repair manual for the lens, which identified the filter holder as part 136JK - Filter Holder Unit.

With this information, I headed to Nikon’s Parts Store, where I discovered you could indeed order a replacement filter caddy—but it would cost $205.73. That’s a lot for a simple plastic part, but at least I knew it was possible to get spares. Interestingly, this high price tag somewhat justifies the costs of the pre-made drop-in filters I had seen earlier, which include features like a gear ring to adjust the filter without removing it from the lens.

Conclusion: How Drop-In Filters Work and Where to Find Replacements

In summary, drop-in filters are simply filter caddies that allow you to use any standard filter by screwing it into the caddy, which then slides into the lens. If you’re looking for replacements, the trick is to treat them as parts rather than accessories and look for them through the manufacturer’s parts store.

I hope this article clarifies the mystery around drop-in filters, especially for photographers new to using lenses like the Nikkor Z 800mm. If you have any more questions, feel free to leave a comment below!