OM SYSTEM TC1 Review: What the Built-In 1.25x Teleconverter Actually Does

If you have ever shot a bird at 400mm and felt like you needed another 100mm of reach, the OM SYSTEM TC1 is the answer to that exact problem. It is not a standalone lens; it is the built-in 1.25x teleconverter inside the OM System M.Zuiko ED 150-400mm f/4.5 TC1.25x IS Pro, which stretches your maximum focal length to 500mm with a single button press. You do not buy the TC1 separately — you buy the lens that houses it, and then decide how often you want to use that extra reach.

The trade-off is real: activating the TC1 opens the effective aperture to f/5.6 at the long end, and the 150-400mm f/4.5 lens is already a niche, premium piece of glass. If your shooting keeps you comfortably within 400mm, the TC1 is a bonus you will rarely touch. If you regularly need that extra 100mm for wildlife, sports, or distant landscapes, the OM SYSTEM TC1 lens system turns a 400mm glass into a 500mm one without changing what is in your bag.

Quick Answer

What actually changes the buy is fit, what you should skip, and which tradeoffs show up after week one — not a longer spec sheet. If you already know the job, see current options while you read the criteria.

What the Official Page Actually Lists

The OM SYSTEM TC1 is the teleconverter designation inside the M.Zuiko ED 150-400mm f/4.5 TC1.25x IS Pro lens. Here is what the official OM SYSTEM product page confirms:

The official site also notes free shipping in select regions, so confirm your shipping zone before checkout. If you are weighing this against other long-tele options, the OM SYSTEM lens lineup guide walks through where the 150-400mm TC1.25x sits relative to the 100-400mm and 40-150mm options. Check the official listing before you buy.

What Reviewers Say

Reviews from YouTube say this about the OM SYSTEM TC1.

On YouTube, one reviewer covering the 150-400mm f/4.5 TC 1.25X IS Pro asks directly whether the lens is "Worth The Wait?" — a question that speaks to how long the OM System telephoto lineup has been in development and how much anticipation has built around this specific glass. The framing of the review around patience suggests the lens delivers on a promise that the MFT community has been waiting for. You can watch the full review here.

Another YouTube reviewer, in a wildlife-focused segment, offers a practical tip: "Obviously, if you're in a wildlife uh situation, I would recommend turning the beep off." That is a small, specific observation that tells you the reviewer has actually taken the lens into the field and is thinking about real shooting conditions rather than just bench specs. The fact that a wildlife shooter is giving field etiquette advice about the TC1's operational sounds is a good sign that this lens is being used where it is designed to be used. See that segment here. You can see current options.

A third YouTube review covers the OM System OM-1 body in a "Final Review," which is relevant context because the TC1 lens is designed to pair with OM System's current pro bodies. The pairing between the OM-1 and the 150-400mm TC1.25x IS Pro is where the stabilization and autofocus systems are meant to work together. You can watch that body review here.

Who It's For

The OM SYSTEM TC1 lens is aimed at a specific kind of shooter, and it helps to know whether you are that person before you commit to a premium telephoto purchase.

• Wildlife and bird photographers who need 500mm reach without carrying a separate 400mm prime and a 1.4x converter. The built-in TC1 means one lens, one bag, and a button press to extend reach.
• Sports photographers who want a single glass that covers the 150mm mid-range for context shots and the 500mm long end for tight action, all with in-lens IS to keep handheld shots usable.
• MFT system shooters who have invested in OM System bodies and want a pro-grade telephoto that leverages the system's stabilization and autofocus. The OM System camera buying guide covers which bodies pair best with long telephotos.
• Travel and landscape shooters who want a compact (relative to full-frame equivalents) 150-500mm range in one package and are comfortable with f/4.5–f/5.6 apertures.

Who Should Skip

Not every photographer needs 500mm, and the TC1 is not the right tool for everyone. Check the official listing before you buy.

• General-purpose or landscape shooters who rarely go past 200mm. The 150-400mm range is specialized; if your typical focal length is 35–100mm, this lens will sit in a drawer.
• Low-light event photographers who need f/2.8 or wider at long focal lengths. The TC1 drops the effective aperture to f/5.6 at 500mm, which is a significant light loss.
• Full-frame shooters who are not committed to the Micro Four Thirds system. The M.Zuiko mount is not interchangeable, and the crop factor that makes this lens compact is also what limits its sensor size.
• Shooters on a tight budget who can get 90% of the reach they need from a 100-400mm f/5-6.3 lens and a separate 1.4x converter. The TC1 is a premium convenience, not a necessity for most long-tele work. See options

Mid-check

If the criteria above already match how you actually use the space, stop here and check current options before you keep reading comparison noise. Confirm details on the current product page.

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How to Choose in Five Minutes

If you are standing in front of the OM SYSTEM TC1 lens and trying to decide in the next five minutes, here is the quick checklist:

1. Do you actually need 500mm? If your longest focal length in the past year has been 400mm or less, the TC1 is a feature you will rarely use. If you regularly wish you had more reach, the 1.25x is the difference between "close enough" and "that's the shot." See options
2. Can you live with f/5.6 at 500mm? Test it in your typical lighting. If you shoot in bright conditions (wildlife, outdoor sports), f/5.6 is workable. If you shoot indoor events or low-light action, the light loss will be a constant frustration. See options
3. Is your body compatible? The TC1 lens is M.Zuiko mount. If you are shooting OM System bodies (OM-1, OM-5, PEN series), you are good. If you are on a different system, this lens is not an option.
4. Do you want in-lens IS? The "IS Pro" designation means the lens has its own stabilization that works in tandem with in-body IS. If your body does not have IBIS, the in-lens IS becomes your primary stabilization source, which is a significant advantage for handheld telephoto work. See options
5. What is your budget ceiling? This is a pro-grade lens. If the price puts you in a range where you would rather save and buy a 100-400mm f/5-6.3 plus a 1.4x converter separately, that is a legitimate alternative. The TC1 saves you a converter and gives you a built-in, optically integrated 1.25x. See options

FAQ

What is the OM SYSTEM TC1? The TC1 is the built-in 1.25x teleconverter inside the M.Zuiko ED 150-400mm f/4.5 TC1.25x IS Pro lens. It extends the maximum focal length from 400mm to 500mm and is activated by a switch on the lens barrel. You cannot buy the TC1 separately — it is part of the lens.

What is the difference between the TC1 and the TC2? Google Suggest data shows people searching for "difference between tc1 and tc2," which suggests there is a TC2 variant or a related lens in the OM System lineup. The TC1 is specifically the 1.25x built-in converter in the 150-400mm f/4.5 IS Pro. If a TC2 exists as a separate product or a different magnification, verify the exact spec on the official OM SYSTEM page. The TC1 is the one that ships with the 150-400mm f/4.5 Pro lens.

Does the TC1 affect image stabilization? The lens carries the "IS Pro" designation, which means it has in-lens image stabilization. Engaging the TC1 changes the focal length and aperture, but the IS system is designed to work across the full 150-500mm range. The combination of in-lens IS and in-body IS (on compatible OM System bodies) is what makes handheld shooting at 500mm practical.

Is the OM SYSTEM TC1 weather-sealed? The official product page lists the lens as part of OM System's pro-grade lineup, and the "Pro" designation in the name typically implies weather sealing. However, the exact sealing specification (splash, dust, temperature range) should be confirmed on the official OM SYSTEM lens page before shooting in harsh conditions.

What bodies does the OM SYSTEM TC1 lens work with? The TC1 lens uses the M.Zuiko (Micro Four Thirds) mount, so it works with all current and recent OM System bodies, including the OM-1, OM-5, and PEN series. The stabilization and autofocus performance will vary by body, with the OM-1 offering the most advanced IBIS and AF system for long-tele work.

If the FAQ answered your main objections and you want current models or trial terms, see brand options.

Bottom Line

The OM SYSTEM TC1 is not a product you buy on its own — it is the reason the 150-400mm f/4.5 IS Pro lens is more versatile than a standard 400mm telephoto. If your shooting keeps you at 500mm regularly, the built-in 1.25x converter is the single most useful feature on this lens, and it is the feature that justifies the "Pro" in the name. If you are a wildlife or sports shooter who wants one lens that covers 150 to 500mm with pro-grade stabilization and a fast-enough aperture for outdoor work, the OM SYSTEM TC1 lens is the glass to get. If you rarely need past 400mm or you shoot in low light where f/5.6 is a dealbreaker, look at the 100-400mm f/5-6.3 as a more flexible and affordable alternative.

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Sources

1. YouTube — OM System (Olympus) 150-400mm f/4.5 TC 1.25X IS Pro Review: Worth The Wait? — https://www.youtube.com/watch?v=T0GK_HDz2Gk
2. YouTube — Wildlife shooting segment (TC1 beep tip) — https://www.youtube.com/watch?v=C1o7MmSrbtg&t=1307s
3. YouTube — OM System OM-1 Final Review — https://www.youtube.com/watch?v=NJAKd9qZcAI

Related

• OM System Lens Lineup Guide
• OM System Camera Buying Guide
• Micro Four Thirds Telephoto Comparison