The Brother MFC-L3720CDW Isn't the Problem. Your Print Specs Are.

Client said the poster looked wrong. I opened the file. The Brother MFC-L3720CDW was set to Letter. The file was 24 by 36 inches. That was the first thing I checked. Not the toner, not the drum, not the network connection. The page size.

I'm a quality control manager at a print services company. I review roughly 200 unique print projects a year, mostly packaging, labels, and point-of-sale material. In 2025 I've rejected about 6% of first deliveries, and most came down to a file setup issue. A wrong size, an RGB-only file, a media type that didn't match the paper. The printer wasn't broken. The instructions were.

This article is about the gap between what you think you're printing and what the printer actually receives. Because once you understand that gap, a lot of 'Brother printer is acting up' searches start to make sense.

The Surface Problem: 'It Prints Wrong'

Here's a classic complaint: 'My Brother MFC series printers print everything too light. Or too small. Or off-center.' The client Googles, finds Brother printer utilities, updates the driver, and the issue stays. Why? Because the issue was never the driver.

Let's use a simple example. You created a caution tape overlay for a poster background. On screen it's a 500 px wide graphic over a 1000 px canvas. Looks great. Then you print it, and the caution tape ends up seven inches wide at the bottom of an 18x24 sheet. The printer didn't 'shrink' it. The file was set to 72 DPI, which made that 500 px graphic 6.94 inches wide. The printer faithfully reproduced those pixels at the physical size they were assigned.

Why does this matter? Because a printer is a measuring device. It converts pixels into physical dimension. If the file has no clear physical size, the driver uses a default. And the default is almost never what you wanted.

Deep Cause #1: 'What Size Is Poster Size?' Is the Wrong Question

This is the most common question I hear: what size is poster size? There is no single answer.

In the US, 11x17 is often called a 'small poster.' 18x24 is a standard poster. 24x36 is the movie-poster size. Outside the US, A3 and A2 are common. And that's just the start. If you don't specify a physical dimension in inches or millimeters, 'poster size' is a guess. The Brother MFC-L3720CDW can't guess. It needs a number.

I've seen a 24x36 file print on Letter because the printer driver was set to 'Scale to fit.' It fit. It also looked like a flyer. Not ideal, but workable? No. Not workable. The customer rejected it.

My experience is based on about 200 mid-size print jobs. If you're working with large-format or textile printing, the same rule applies, just with different numbers.

Deep Cause #2: Color Is a Translation, Not a Copy

The next reason a print looks wrong is color. Screens use RGB. Ink uses CMYK. When you send an RGB file to a printer, the driver translates it. The Brother MFC-L3720CDW's default translation is reasonable for everyday documents. It is not a contract proof for a poster.

We had a job with a caution tape overlay for a warning label. The yellow looked bright neon on the client's screen. They expected neon. It printed as a dark mustard. Why? Because the file was RGB, the overlay was saturated, and the CMYK translation brought it down. We had to rerun the whole order.

Did I blame the printer? No. The file should have been converted to CMYK, or the client should have approved a proof. The printer did exactly what it was told.

This is where Brother MFC series printers actually help. The Brother printer utilities let you set color mode, paper type, and quality. If you're on a default profile and printing marketing material, you're leaving color to luck. The question isn't 'why is the blue different?' It's 'did I tell the printer what kind of output this is?'

Deep Cause #3: Utilities Give You Control. They Don't Fix Bad Files.

Let's talk about Brother printer utilities for a second. The driver, the firmware update tool, iPrint&Scan—these are all about giving you control. Choosing the correct paper source, matching media type, updating the color table. They don't detect that your poster is 24x36 while the paper tray is Letter. That's not a software bug. That's a spec gap.

The most common phrasing I hear: 'The printer is printing everything smaller than it should.' In almost every case, the paper size in the file is set to a different size than the selected tray. The printer tells you. The warning says 'paper size mismatch.' But people ignore it and click 'continue.' Then the image is scaled to fit the tray, and the output is 'wrong.'

On the Brother MFC-L3720CDW, that warning isn't optional. It's a clue. If you see a paper size mismatch, stop. Don't click continue. Check the file page size, not just the print dialog size.

The Cost of Getting This Wrong

Spec errors are expensive. In our Q1 2024 quality audit, 18% of our reprints were caused by incorrect file setup. That's from 40 reprint events we tracked. Hardware failures accounted for 7%. The conclusion is clear.

One example: a rush order for retail packaging labels. The product was a Speedo Hyper Flyer goggle. The label size was specified as 1.5 inches by 1.5 inches. The designer thought 2 inches looked better on screen. We approved the proof without checking the physical measurement. When the labels arrived, they didn't fit the packaging. The reprint cost us $1,400 and two days of delay. That's not the printer's fault. It's a measurement fail.

Now, a $1,400 reprint is annoying. In other jobs, it's worse. A failed signage run can cost a client event. A bad label can break a product launch. I've seen one quality issue cost our company $22,000 in rework and overtime. That happened during a client launch week in 2023.

What I Actually Check Now (And You Should Too)

I know this sounds simple. But simple fixes get skipped under deadline pressure. Three things before you hit print:

1. Set the physical size first. Don't ask 'what size is poster size?' Ask 'what size is this piece of paper?' Put that exact width and height in the document and the print driver. Include bleed if the job has one.
2. Choose the right media type. Plain paper, coated paper, heavy paper, labels—each changes how much ink or toner gets laid down. Brother MFC series printers have a media type setting for a reason. Use it.
3. Use Brother printer utilities to update firmware and set defaults. This won't save you if the file is 2x2 inches and the packaging needs 1.5x1.5. But it will make sure the driver is current and the printer knows what it's holding.

If you're printing a poster, don't let the driver 'fit' anything. Select 'Actual Size' in the scaling option. This is a small thing. It's also the difference between a poster and a flyer.

Bottom Line

The Brother MFC-L3720CDW isn't a difficult printer. It's just literal. It prints what you spec in the file and the driver. If the output looks wrong, check the specs before you blame the hardware.

I went back and forth for two weeks on whether to standardize our poster orders as 18x24 or 24x36. 18x24 cost less to ship. 24x36 felt more like a poster. I chose 24x36. Even after choosing it, I kept second-guessing. What if clients complain about the shipping cost? The first order came in, printed at 24x36, and the client said 'this finally looks like a real poster.' I relaxed. Not everyone needs that size, but the lesson stayed with me.

What was best practice in 2020 may not apply in 2025. Print workflows have changed. But the fundamentals haven't: physical size, media type, color mode, proofing. Get those right, and your Brother MFC series printers will do the same thing they've always done—produce exactly what you asked for. No more, no less.