You’re comparing a 35mm f/1.8 lens on an APS-C camera with a 50mm f/1.8 on full frame, and the numbers don’t line up. The APS-C lens frames tighter than its focal length suggests. It seems to blur the background less, too. And when you read about it online, one article says crop factor multiplies your ISO, while another says it never changes your exposure. So who’s right?
Both, because they answer different questions. This APS-C to full frame calculator converts focal length and aperture to their full-frame equivalents, and the page below shows how the ISO question resolves once you name the comparison. A 35mm f/1.8 at ISO 400 on a 1.5× APS-C camera gives the same picture as a 52.5mm f/2.7 at ISO 900 on full frame. You’ll get the formulas, tables for Sony, Nikon, Fujifilm, Canon and Micro Four Thirds, and a section on how a speed booster changes the maths.
If you adapt lenses, the guide to speed booster effective aperture covers the exposure side in depth. Here we stay with the conversion itself: no hidden constants, no tricks, and every figure comes from a formula you can run on your phone. It also answers the question behind the “35mm equivalent” number printed in camera specs.
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Table of Contents
- APS-C to Full Frame Calculator
- How Do You Convert APS-C to Full Frame?
- What Is the Crop Factor of APS-C?
- APS-C to Full Frame Focal Length Conversion Table
- What Is the Full Frame Equivalent Aperture?
- Does Crop Factor Change ISO?
- Quick Answers About APS-C to Full Frame
- How Does a Speed Booster Change the APS-C to Full Frame Maths?
- What Lens Do You Need for a Full Frame Look on APS-C?
- Frequently Asked Questions
APS-C to Full Frame Calculator
Type your focal length, aperture and crop factor, keep the ratio at 1.0×, and the calculator returns the full-frame equivalent focal length and aperture. Pick a camera from the list to fill in its crop factor, or type your own. Add an ISO to see the full-frame equivalent ISO. If you use a speed booster, choose its ratio and the same calculator includes it.
APS-C to full frame calculator
Results update as you type. Nothing is sent to a server.
Exposure follows the effective aperture. Depth of field follows the full-frame equivalent aperture.
Speed boosters are made for sensors smaller than the lens image circle. On a full-frame or larger sensor the shrunken image circle will not cover the frame, so expect vignetting.
The highlighted card is the full-frame equivalent focal length, and the card next to it is the equivalent aperture.
How Do You Convert APS-C to Full Frame?
Multiply by the crop factor. The full-frame equivalent focal length is the lens focal length × crop factor, the equivalent aperture is the f-number × crop factor, and the equivalent ISO is the ISO × crop factor². The shutter speed doesn’t change.
Simply put, a full-frame equivalent describes a picture, not a lens setting. It’s the full-frame photo that would have the same field of view, the same depth of field and about the same noise as your APS-C shot. Here’s the conversion for a 35mm f/1.8 lens at ISO 400 and 1/200 s on a 1.5× APS-C camera:
- Focal length: 35mm × 1.5 = 52.5mm.
- Aperture: f/1.8 × 1.5 = f/2.7.
- ISO: 400 × 1.5² = 400 × 2.25 = ISO 900.
- Shutter speed: 1/200 s stays 1/200 s.
That’s the standard definition of photographic equivalence. Wikipedia’s article on image sensor format lists the same four conditions: equal field of view, equal depth of field, equal aperture diameter and equal exposure time.
Three multipliers and one unchanged number cover the whole conversion.
What Is the Crop Factor of APS-C?
Most APS-C cameras have a 1.5× crop factor, and Canon APS-C is about 1.6×. Micro Four Thirds is 2.0×, for comparison.
Simply put, crop factor is the full-frame diagonal (about 43.3mm) divided by your sensor’s diagonal. A smaller sensor sees a smaller part of the image the lens projects, so the same lens frames tighter.
| Sensor format | Typical size | Diagonal | Exact crop factor | Value used on this page |
|---|---|---|---|---|
| Full frame | 36 × 24mm | 43.3mm | 1.0 | 1.0 |
| APS-C (Sony, Nikon, Fujifilm, Pentax) | 23.5 × 15.6mm | 28.2mm | 1.53 | 1.5 |
| APS-C (Canon) | 22.3 × 14.9mm | 26.8mm | 1.61 | 1.6 |
| Micro Four Thirds | 17.3 × 13mm | 21.6mm | 2.0 | 2.0 |
Why do some calculators say 1.52 or 1.53 instead of 1.5? Because the exact figure is 43.3 ÷ 28.2 ≈ 1.53, and 1.5 is the rounded value most people use. The difference is small. A 50mm lens gives 75mm with 1.5 and about 77mm with 1.53. Pick one value and use it consistently. This page uses 1.5 and 1.6, like the calculator’s camera list, and sensor sizes vary slightly by model.
The exact figure is a diagonal ratio, and the everyday figure is its rounded version.
APS-C to Full Frame Focal Length Conversion Table
A 35mm lens frames like 52.5mm on Sony, Nikon and Fujifilm APS-C and like 56mm on Canon APS-C. Here are the focal lengths people look up most.
| Lens focal length | Sony, Nikon, Fujifilm APS-C (1.5×) | Canon APS-C (1.6×) | Micro Four Thirds (2.0×) |
|---|---|---|---|
| 16mm | 24mm | 25.6mm | 32mm |
| 23mm | 34.5mm | 36.8mm | 46mm |
| 35mm | 52.5mm | 56mm | 70mm |
| 50mm | 75mm | 80mm | 100mm |
| 56mm | 84mm | 89.6mm | 112mm |
The equivalent focal length is a field-of-view label, not a real focal length. Your 35mm lens is still a 35mm lens. It just frames the scene the way a 52.5mm lens would on full frame, which is what spec sheets call the 35mm equivalent focal length. To go the other way, divide: a full-frame 50mm view needs about a 33mm lens on 1.5× APS-C.
Multiply the focal length by the crop factor to compare framing, and divide to find the lens you’d need.
What Is the Full Frame Equivalent Aperture?
Multiply the f-number by the crop factor. An f/1.8 lens on 1.5× APS-C gives the depth of field and total light of about f/2.7 on full frame at the same framing.
| Lens aperture | Sony, Nikon, Fujifilm APS-C (1.5×) | Canon APS-C (1.6×) | Micro Four Thirds (2.0×) |
|---|---|---|---|
| f/1.4 | f/2.1 | f/2.24 | f/2.8 |
| f/1.8 | f/2.7 | f/2.88 | f/3.6 |
| f/2 | f/3 | f/3.2 | f/4 |
| f/2.8 | f/4.2 | f/4.48 | f/5.6 |
| f/4 | f/6 | f/6.4 | f/8 |
This is a comparison number, not a setting. Don’t use it to meter: f/2.8 on APS-C still exposes like f/2.8. The equivalent aperture tells you how blurry the background will be and how much total light the lens gathers, compared with a full-frame lens at the same field of view. Joseph James explains why the aperture diameter, not the f-number, sets both depth of field and total light for a given scene, framing and shutter speed.
The equivalent aperture compares looks, and the lens still exposes by its own f-number.
Does Crop Factor Change ISO?
Not for exposure, yes for equivalence. The same f-number, shutter speed and ISO give the same brightness on any sensor. But to match the full-frame picture’s noise and total light, the full-frame ISO must be the APS-C ISO × crop factor².
| Question | Answer | Example |
|---|---|---|
| Same brightness with the same settings? | Yes. No ISO change is needed | f/4, 1/200 s, ISO 400 gives the same brightness on APS-C and full frame |
| Same picture (field of view, depth of field, shutter speed) and similar noise? | Full frame needs the f-number × crop and the ISO × crop² | APS-C f/1.8, 1/200 s, ISO 400 matches full frame f/2.7, 1/200 s, ISO 900 |
Here’s why the numbers work out that way. A full-frame lens at f/2.7 and a 52.5mm focal length has the same opening as an APS-C lens at f/1.8 and 35mm, so both gather the same total light. But that light spreads over 2.25 times the area (1.5²), so brightness per area is lower. Raising the ISO by 2.25 brings the full-frame picture back to the same brightness. The same idea explains why a speed booster adds exposure but not total light, which we break down in do speed boosters really add light.
| APS-C or MFT ISO | Full-frame equivalent, 1.5× APS-C | Full-frame equivalent, 1.6× Canon APS-C | Full-frame equivalent, 2.0× MFT |
|---|---|---|---|
| 100 | 225 | 256 | 400 |
| 200 | 450 | 512 | 800 |
| 400 | 900 | 1024 | 1600 |
| 800 | 1800 | 2048 | 3200 |
| 1600 | 3600 | 4096 | 6400 |
| 3200 | 7200 | 8192 | 12800 |
A peer-reviewed analysis in Optical Engineering reaches the same conclusion: equivalent photos use the same total light, so their noise is of the same order of magnitude. That holds when the sensors are of comparable technology. Real cameras differ, so treat the table as a guide, not a guarantee.
Exposure settings stay the same across sensors, and the ISO changes only when you want an equivalent picture.
Quick Answers About APS-C to Full Frame
What Does “Full Frame Equivalent” Mean?
Simply put, a full-frame equivalent is the full-frame setup that would produce the same picture as your APS-C one: the same field of view, depth of field and shutter speed, with similar noise. It’s built by scaling the focal length and aperture by the crop factor and the ISO by its square. It matters most when you compare lenses or systems, not when you set exposure.
APS-C to Full Frame at a Glance
| Aspect | Details |
|---|---|
| Symptom | An APS-C lens frames tighter and blurs less than its focal length and f-number suggest |
| Root Cause | The smaller sensor sees a smaller part of the image circle, by a factor of about 1.5 (Canon 1.6) |
| Fix | Multiply focal length and f-number by the crop factor, and ISO by the crop factor squared |
| Result | 35mm f/1.8 at ISO 400 on 1.5× APS-C equals 52.5mm f/2.7 at ISO 900 on full frame |
| Applies To | Comparing looks and noise across sensor sizes, not metering on your own camera |
When Does This Apply?
It applies when you compare the same scene across sensor sizes: choosing between systems, matching a full-frame look or judging a lens review. It doesn’t apply to your exposure settings, which stay the same on any camera, or to how the lens renders, which a calculator can’t predict.
How Does a Speed Booster Change the APS-C to Full Frame Maths?
A speed booster multiplies your focal length and f-number by its ratio before the crop factor applies, so it moves APS-C closer to full frame. A 0.71× booster on a 1.5× APS-C camera gives a combined crop of about 1.07×.
| Full-frame lens | On 1.5× APS-C, no booster (in full-frame terms) | On 1.5× APS-C with a 0.71× booster (in full-frame terms) |
|---|---|---|
| 24mm f/1.4 | 36mm f/2.1 | 25.56mm f/1.49 |
| 35mm f/1.4 | 52.5mm f/2.1 | 37.28mm f/1.49 |
| 50mm f/1.8 | 75mm f/2.7 | 53.25mm f/1.92 |
| 85mm f/1.4 | 127.5mm f/2.1 | 90.53mm f/1.49 |
The equivalent ISO still uses the camera’s crop factor only, because the sensor is still APS-C. Take a 50mm f/1.8 lens with a 0.71× booster at ISO 400. The sensor sees f/1.28, the full-frame equivalent is 53.25mm f/1.92, and the equivalent ISO is 400 × 2.25 = 900. The brightness matches, since (1.92 ÷ 1.28)² is exactly 2.25. The speed booster crop factor table shows the combined crop factors and which ratio covers which sensor.
A booster doesn’t change the ISO rule, but it does move the focal length and aperture much closer to full frame.
What Lens Do You Need for a Full Frame Look on APS-C?
Divide the full-frame focal length and f-number by the crop factor. A full-frame 50mm f/1.8 look needs about a 33mm f/1.2 lens on 1.5× APS-C.
| Full-frame look | 1.5× APS-C lens needed | 1.6× Canon APS-C lens needed | 2.0× MFT lens needed |
|---|---|---|---|
| 35mm f/1.4 | 23.33mm f/0.93 | 21.88mm f/0.88 | 17.5mm f/0.7 |
| 50mm f/1.8 | 33.33mm f/1.2 | 31.25mm f/1.13 | 25mm f/0.9 |
| 85mm f/1.8 | 56.67mm f/1.2 | 53.13mm f/1.13 | 42.5mm f/0.9 |
Lenses that fast are rare. A 56mm f/1.2 APS-C lens would match an 85mm f/1.8 full-frame look, and many of the faster entries in the table don’t exist as real lenses. That’s why shallow-focus looks are harder on a smaller sensor. A speed booster helps close the gap, and the calculator’s “Find the ratio I need” mode shows the ratio for a target full-frame focal length.
Divide to find the lens, then check whether a lens like that actually exists.
Frequently Asked Questions
What is the full frame equivalent of a 35mm lens on APS-C?
About 52.5mm on Sony, Nikon and Fujifilm APS-C (35 × 1.5) and 56mm on Canon APS-C (35 × 1.6). On Micro Four Thirds the same lens frames like 70mm. The lens itself stays a 35mm lens.
What is the full frame equivalent of a 50mm lens on APS-C?
About 75mm on a 1.5× APS-C camera and 80mm on Canon's 1.6× bodies. Use 1.53 instead of 1.5 and you get roughly 77mm, so the exact figure depends on the sensor size.
Does an f/2.8 APS-C lens act like f/4.2 on full frame?
For depth of field and total light at the same framing, yes. For exposure, no. The lens still exposes like f/2.8, so f/2.8, 1/200 s and ISO 400 gives the same brightness on both cameras.
Does crop factor change my exposure?
No. The same f-number, shutter speed and ISO give the same brightness on any sensor. Crop factor only changes how a picture looks and how much total light it uses, which matters when you compare systems.
Do I need to change ISO when I switch from APS-C to full frame?
Only if you want an equivalent picture with matching noise. Then the full-frame ISO is the APS-C ISO × crop factor². For ordinary shooting, keep your usual ISO and let the exposure meter decide.
How do I convert full frame to APS-C focal length?
Divide by the crop factor. A full-frame 85mm view needs about a 57mm lens on 1.5× APS-C and 53mm on Canon 1.6×. Aperture works the same way, so f/1.8 becomes about f/1.2.
Why do some calculators use 1.52 or 1.53 for APS-C?
The exact figure is the full-frame diagonal (43.3mm) divided by a 28.2mm APS-C diagonal, about 1.53. Most people round it to 1.5. The difference is under 3%, so a 35mm lens gives 52.5mm or about 53.7mm.
Can a speed booster make APS-C behave like full frame?
Almost. A 0.71× booster on a 1.5× camera gives a combined crop of about 1.07×, close to full-frame framing. It brings the focal length and aperture much closer to full frame, though the sensor and the adapter glass still differ.
So that’s the APS-C to full frame conversion in one line: multiply focal length and aperture by the crop factor, and ISO by the crop factor squared. A 35mm f/1.8 at ISO 400 on 1.5× APS-C equals a 52.5mm f/2.7 at ISO 900 on full frame, with the same shutter speed. It’s a way to compare pictures, not a way to meter them, so keep your own camera’s settings as they are.
This sits inside the wider lens-maths picture: how crop factor, aperture and adapters combine across sensor sizes. Exact sensor sizes vary a little by model, and adapters keep changing, so check the maker’s current spec sheet in 2026 when exact numbers matter.
Scroll back up to run your own lens through the calculator, bookmark this page for the tables, and share it with the friend who asks why their APS-C lens looks tighter than the number on the barrel.