Sigma 90mm f/2.8 DG DN Review: Leica Quality for $600 (L-Mount)

This is the second of two Sigma lens reviews I have done recently and this lens is no slouch either. The 90mm f2.8 DG DN Sigma lens is a very well made little prime lens and this particular copy is for the L mount for Leica and Panasonic cameras. I am sure Sigma makes this lens for other lens mounts as well, but I dont have that list with me so I cant speculate past that.

Sigma 90mm f/2.8 DG DN: Technical Specifications

Before we dive into the hands-on experience, here are the specs:

Optical Design:

• Focal length: 90mm

• Maximum aperture: f/2.8

• Minimum aperture: f/22

• Aperture blades: 9 (rounded for smooth bokeh)

Physical Specs:

• Mount: L-mount (Leica SL/CL, Panasonic S-series)

• Filter size: 55mm

• Length: 2.4 inches (61.6mm)

• Weight: 10.4 oz (295g)

• Minimum focus distance: 19.7 inches (50cm)

Construction:

• All-metal barrel

• Aperture ring with 1/3 stop detents

• AF/MF switch on lens barrel

• Weather sealing: No (one downside vs Leica)

Price:

• Sigma 90mm f/2.8 DG DN: ~$600

• Leica APO-Summicron-SL 90mm f/2 ASPH: ~$5,395

Yeah, that's not a typo. The Leica costs nine times more than the Sigma. Let's see if that price difference is justified!

What is 90mm Good For? Use Cases and Focal Length

If you're not familiar with 90mm as a focal length, let me explain why this is such a useful lens to have:

Portrait Photography: 90mm is a classic portrait focal length! It gives you nice compression, flattering perspective, and enough working distance that you're not right in your subject's face. The f/2.8 aperture provides good subject separation without going overboard. This is what I'd grab for environmental portraits where I want context but still want the subject to stand out.

Street Photography: At 90mm, you get compressed perspective that makes street scenes feel more intimate. You can shoot from across the street without being obvious, and the focal length picks out details in a way that 35mm or 50mm just can't. It's not a run-and-gun street lens, but for deliberate composition? It's great!

Detail Work: Need to photograph architectural details, signage, or anything where you want isolation without getting too close? 90mm is perfect. I use this focal length all the time for documenting buildings and urban details in Chattanooga.

What 90mm is NOT good for: Wide landscapes (too narrow), group photos in tight spaces (you'll run out of room to back up), and anything requiring fast reaction (it's a slower, more deliberate focal length). Know your lens's strengths!

The Sigma 90mm f/2.8 DG DN with its lens hood attached. Notice how the hood is almost as big as the lens itself! This is a genuinely compact 90mm prime lens.

In the photo below you can see how small the lens actually is. The lens hood takes up almost as much space as the lens itself. That is crazy! With the all metal construction and well made optical formula, this lens is also punching up as they say.

Size comparison showing how small this lens actually is. The lens hood takes up almost as much space as the lens itself. That's crazy for a 90mm focal length! With all-metal construction and excellent optics, this little lens is punching way above its weight.

Some notable differences between the Sigma lens and my Leica counterparts are that the Sigma lens actually has an aperture ring on it that also has 1/3 stop detents. This is really nice as it allows manual aperture control to be basically mapped to a control surface that photogs are accustomed to using. If you want the usual camera control for the aperture, then simply turn the aperture ring to the “A” position and your ready to go. Ít couldn’t be simpler.

The aperture ring on the Sigma 90mm with 1/3 stop detents. This is a really nice feature that allows manual aperture control mapped to a control surface photographers are already used to. Turn it to "A" for camera-controlled aperture. Simple and intuitive!

The next thing they did on the lens that I am not so sure I like yet is to put a switch to choose between manual and automatic focus. The Leica lenses use a software control to do this and it is pretty simple to implement and once you get used to doing it that way it really is a good system. There are less openings in the lens to let water in and the control is right they with the various auto focus modes all in one spot. The Sigma system has you choose manual or auto on the lens and then if you choose auto, you have to further goto the software and choose the automatic mode you want. It makes choosing autofocus a two step affair. This is probably just a user issue where I lack practice with the lens, but this seems a little clumsy compared to the Leica process. It is possible that Leica didn’t share all the tech needed to make this happen, I don’t know, but like I said I am on the fence on this one.

The AF/MF switch on the lens barrel. This is the one design choice I'm not sold on yet. Leica lenses use software control for focus modes in one step. The Sigma requires you to switch here first, then choose the AF mode in the camera menu. It's a two-step process that feels clumsy compared to Leica's system. Still works fine, just takes getting used to!

Lastly is image quality. The Sigma has it. It produces sharp, distortion free images with good color and exposure. What more can I say here? It really is amazing what you get for the price. These lenses can run with the big boys, in my opinion, just fine. If you pixel peep deep enough you might find fault in them, but only photographers do that. The normal person never digs into the corners or zooms into 500% on a photo so I am not going to rate this lens like that either. The photos look wonderful…just look at the ones below.

Sample Photos: What This Lens Can Do

Let me show you what this lens can actually produce in real-world use. These are all shot with the Sigma 90mm f/2.8 on my Leica SL2:

Sample photo shot with the Sigma 90mm f/2.8 on my Leica SL2. Look at the sharpness, color rendering, and contrast! This lens produces distortion-free images with excellent detail. What more can you ask for at this price point?

Look at the sharpness across the frame! The colors are accurate without being oversaturated, the bokeh is smooth and not distracting, and the compression at 90mm makes these compositions work. The first photo shows how this lens handles contrast and detail in mixed lighting. The second demonstrates subject isolation at f/2.8. The third shows color rendering in challenging light.

This is what you're getting for $600. Not "budget lens performance." This is legitimate high-quality glass that happens to cost less than the Leica equivalent.

One thing to note: these photos weren't babied. I was shooting handheld in various lighting conditions, some shots were wide open at f/2.8, and I didn't do any special post-processing beyond my normal workflow. This is real-world performance, not controlled test charts!

Another example of what this lens can do. The 90mm focal length gives you nice compression and the f/2.8 aperture provides good subject separation. The bokeh is smooth and not distracting. This is Leica-quality glass at a fraction of the cost!

More proof that the Sigma 90mm delivers excellent image quality in real-world use. Colors are accurate without being oversaturated, detail is sharp across the frame, and the lens handles mixed lighting well. These aren't test charts, this is actual photography!

Final sample showing the Sigma 90mm's capabilities. Shot handheld in Chattanooga during a block party. The lens is sharp, colors look great, and the compression at 90mm makes the composition work. If you want great glass at a fraction of Leica's price, this lens is the ticket!

Sigma vs Leica: Is the Price Difference Worth It?

Let's address the elephant in the room: Leica makes a 90mm lens for L-mount. The Leica APO-Summicron-SL 90mm f/2 ASPH costs about $5,400. The Sigma costs $600. That's a $4,800 difference.

What do you get for that extra $4,800?

The Leica advantages:

• One stop faster (f/2 vs f/2.8)

• APO designation (apochromatic correction, minimal chromatic aberration)

• Legendary Leica color rendering and micro-contrast

• Full weather sealing

• Leica brand prestige (if that matters to you)

• Probably slightly sharper wide open (though the Sigma is already sharp!)

The Sigma advantages:

• Costs $600 instead of $5,400

• Still produces excellent images (as you can see from my samples!)

• Aperture ring with detents (Leica's is clickless)

• Compact and lightweight

• You save $4,800 that you can spend on other lenses or, you know, food!

My take: If you're a professional portrait photographer who needs f/2 and perfect optical performance for paying clients? Maybe the Leica is worth it. If you're a Leica SL2 shooter who wants excellent 90mm performance without spending a small fortune? The Sigma is absolutely the right choice.

I'd rather have the Sigma 90mm f/2.8 plus a Sigma 35mm and 65mm for the same price as one Leica 90mm. That's three lenses versus one! Unless you're chasing that last 5% of optical perfection, the Sigma is the smart buy.

Pros, Cons, and Who Should Buy the Sigma 90mm f/2.8

Let me break down the good and the not-so-good about this lens:

What I Love (Pros):

• Image quality is excellent: Sharp, great color, minimal distortion

• Compact size: Fits easily in a bag, lens hood is bigger than the lens!

• Aperture ring with detents: Manual aperture control feels great

• All-metal construction: Feels solid and well-made

• Price: $600 vs $5,400 for the Leica equivalent

• Real f/2.8: Not a variable aperture zoom, consistent light gathering

What I Don't Love (Cons):

• Two-step focus mode selection: AF/MF switch on lens PLUS software menu selection feels clumsy compared to Leica's one-step software control

• Only f/2.8: If you need f/2, you'll have to step up to the Leica (and pay 9x more)

• No weather sealing: Leica lenses are weather sealed, this isn't

• Learning curve: Takes some getting used to if you're coming from Leica's system

Who Should Buy This Lens:

• Leica SL2 or Panasonic S-series shooters on a budget

• Portrait photographers who want 90mm without spending $5,000+

• Anyone building an L-mount lens kit and prioritizing value

• Street photographers who like compressed perspective

• Photographers who appreciate manual aperture rings

Who Should Skip This Lens:

• People who absolutely need f/2 or faster

• Photographers who require weather sealing for their work

• Anyone who already owns the Leica 90mm f/2 (obviously!)

• Wide-angle shooters (this isn't your lens!)

Final Thoughts

So in conclusion, if you want great glass at a fraction of the cost of Leica, this lens is just the ticket. Sigma has done a complete 180 from the last time I used one over a decade ago and that makes me happy.

Here's my bottom line: The Sigma 90mm f/2.8 DG DN is the lens Leica SL2 shooters should buy if they can't justify $5,400 for the Leica version. And honestly? Most people can't and shouldn't justify that price difference. The Sigma produces excellent images, feels solid, and costs less than many Leica lens hoods!

The only real downsides are the two-step focus mode selection (which is a user interface annoyance, not a deal-breaker) and the lack of weather sealing. If those don't bother you, this lens is a no-brainer for L-mount shooters.

Sigma has seriously stepped up their game in recent years. I remember using Sigma lenses a decade ago and being underwhelmed. These new DG DN lenses for mirrorless mounts? They're competitive with first-party glass at a fraction of the price. This is exactly what the L-mount system needs—excellent third-party options that don't compromise on quality.

Would I rather have the Leica 90mm f/2? Sure, if someone else is paying for it! But would I rather have the Sigma 90mm plus four other Sigma primes for the same money? Absolutely. That's the math that makes sense for most photographers.

Now get your camera out and go take a picture with it!