# Exposure Calculatorto Compare Any Two Camera Exposures

How many stops difference? What are the EV numbers? Find an Equivalent Exposure?

There are two modes here:

• Enter two camera exposures to calculate EV Difference in exposures A and B.
• Or, find an Equivalent Exposure in B, to be equal exposure as specified in A.
 1. Difference A B Shutter Speed 512 400 360" *½ 320 256" 200" 180" *H 160" 128" 100" 90" *H 80" 64" 50" 45" *H 40" 30" 25" 20" *H 20" 16" 13" 10" *H 10" 8" 6" 6" *H 5" 4" 3" 3" *H 2.5" 2" 1.6" 1.5" *H 1.3" 1" 1/1.3 1/1.5 *H 1/1.6 1/2 1/2.5 1/3 *H 1/3 1/4 1/5 1/6 *H 1/6 1/8 1/10 1/10 *H 1/13 1/15 1/20 1/20 *H 1/25 1/30 1/40 1/45 *H 1/50 1/60 1/80 1/90 *H 1/100 1/125 1/160 1/180 *H 1/200 1/250 1/320 1/350 *H 1/400 1/500 1/640 1/750 *H 1/800 1/1000 1/1250 1/1500 *H 1/1600 1/2000 1/2500 1/3000 *H 1/3200 1/4000 1/5000 1/6000 *H 1/6400 1/8000 1/10000 1/12000 *½ 1/12800 1/16000 1/20000 1/24000 *½ 1/25600 1/32000 f/stop f/0.5 f/0.56 f/0.59 *H f/0.63 f/0.71 f/0.79 f/0.84 *H f/0.89 f/1 f/1.1 f/1.2 *H f/1.3 f/1.4 f/1.6 f/1.7 *H f/1.8 f/2 f/2.2 f/2.4 *H f/2.5 f/2.8 f/3.2 f/3.3 *H f/3.5 f/4 f/4.5 f/4.8 *H f/5.0 f/5.6 f/6.3 f/6.7 *H f/7.1 f/8 f/9 f/9.5 *H f/10 f/11 f/13 f/13 *H f/14 f/16 f/18 f/19 *H f/20 f/22 f/25 f/27 *H f/28 f/32 f/36 f/38 *H f/40 f/45 f/50 f/54 *H f/57 f/64 f/72 f/76 *H f/80 f/90 f/100 f/108 *H f/114 f/128 f/145 f/150 *½ f/160 f/180 f/200 f/220 *½ f/230 f/260 f/290 f/300 *½ f/320 f/360 f/400 f/440 *½ f/460 f/520 EV (settings) Working ISO 1.56 2 2 *½ 2.5 3 4 4 *½ 5 6 8 9 *½ 10 12 16 18 *½ 20 25 32 35 *½ 40 50 64 70 *½ 80 100 125 140 *½ 160 200 250 280 *½ 320 400 500 560 *½ 640 800 1000 1100 *½ 1250 1600 2000 2200 *½ 2500 3200 4000 4500 *½ 5000 6400 8000 8800 *½ 10000 12800 16000 17600 *½ 20000 25600 32000 36000 *½ 40000 51200 64000 72000 *½ 80000 102400 128000 144000 ½ 160000 204800 256000 288000 ½ 320000 409600 512000 576000 ½ 640000 819200 Light ValueEV at ISO 100 Find Equivalent Exposure B, to be equal to A 2. Aperture Preferred (the shutter changes) 3. Shutter Preferred (the f/stop changes) 4. Manual settings (the ISO changes)

Please report ( Here ) any problems with the calculator, or with any aspect of this or any page. It will be appreciated, thank you.

The selections above provide the possible settings (of full, third, half stops).
Full stops are Green. Third stops are Blue. Half stops are Red, also flagged with .
The error NaN should Not show up here, but it would mean the input is Not a Number.

The calculator range is large, but not quite infinite.
The f/stop range is f/0.5 to f/520 (20 EV).
Shutter speed range is 512 seconds to 1/32000 second (24 EV).
ISO is from ISO 1.56 to 819200 (19 EV). Seems adequate.

• 1. Exposure Difference makes comparison of two exposures possible by first converting both EV results to ISO 100 (as if metered at the same ISO value). This arbitrary conversion to ISO 100 is called "Light Value" (next page). ISO 100 is Not magic or unique or even special. We could use any number, but 100 is familiar and comfortable for us, it's only the popularity that makes it seem special.
• 2. - 4. Equivalent Exposure. You can set values into B, and then specify the one value the computer can change to make it be an equivalent exposure, to be the same as is specified in A. You can of course then change your settings and click again. This is NOT Auto ISO, it is fixed ISO. If the settings are already an equivalent exposure (0 EV difference), then of course no visible change will occur.
• The camera settings EV term used here is just EV, which includes only shutter speed and f/stop (does Not specifically include ISO). EV is from film days, when ISO was a constant determined by the roll of film in the camera. The formula to calculate EV does not include the ISO number, but of course the choice of proper camera settings used definitely does depend on ISO. It works for the ISO you are using.

EV is is that Exposure Value that a light meter would read when set to that ISO (the default numbers represent full bright sunlight). It is how the EV Chart would be used, we would use the settings on that indicated EV chart row, for the proper metered exposure at that ISO (example next page). EV is technically computed from only the camera settings (only shutter speed and f/stop are computed), but those choices course depend on the ISO value. If we change ISO, it changes the metered EV and the settings we would select.

It is the EV in the EV chart where that combination of equivalent settings is found, and appears to be independent of ISO in that way. However, when the light meter is set to an ISO and then it meters EV X, then the EV chart row X is the right settings for a correct exposure at that same ISO. ISO is of course very important. A different ISO would meter different settings on a different EV row.

Basically, the EV number is the "name" of the set of Equivalent Exposure combinations of f/stop and shutter speed found on one row of the EV chart.

Exposure Value and the EV Chart is covered on the next page. But either of the default settings above give the same equivalent metered exposure in typical bright sunlight. Both A and B are also the Sunny 16 Rule (except Sunny16 is often 1/3 stop more exposure than the EV system meters). The actual meters doing this are shown on next page. This is two actual real world meterings of two equivalent exposures.

Concept is, for the two ISO values, the light meter reads EV 15 or 18. Look up either EV 15 or EV 18 in the EV chart, and it will show these settings appropriate for that ISO. That's what the chart's about. Since ISO 800 exposes 3 EV brighter, it offsets the 1/1000 second shutter speed, so these two are Equivalent Exposures. The purpose of this calculator is to similarly compare any two exposures.

If just wanting to compare individual relationships (f/stops, shutter speed, or ISO), then see the f/stop calculator.

We could say the EV formula is independent of ISO (next page). However, the settings (shutter speed and f/stop) are selected with attention to the ISO (cause and effect), and certainly we do get a different EV with a different ISO. A greater EV number implies a brighter light, so less exposure is needed, which is a greater EV in a lower row in the EV chart. EV number is about the settings, and EV increases in the opposite direction from the exposure required (one EV is same amount as one stop, both are a 2x change in exposure).

The calculators top "EV (settings)" value is computed from the settings entered, and (assuming a correct exposure) is what a light meter will read at the working ISO, and this is the EV to look up in a EV chart for use at that ISO value. The actual camera setting choices will have already been affected by that ISO, so this EV is not further affected by the ISO that we enter now.

The entered ISO values (the working ISO actually used by the setting exposure) are used for the "EV at ISO 100" values (often called Light Value), which simply converts both exposures from these values used, to be the same ISO 100, for purposes to compare the difference in the exposures for equality (ISO 100 is not a magic number, any SAME ISO value allows exposure comparison). The box above is organized its way to indicate that this ISO entry does not affect the top EV value again, but this ISO (now known) does affect converting to EV at ISO 100. The camera setting ISO used, and the calculator ISO entered, really must of course match for any reasonable use.

Specific example: The calculator defaults when this page loads are:

A: 1/1000 second, f/16, for EV 18 at ISO 800
B: 1/125 second,   f/16, for EV 15 at ISO 100.

Settings EV (without effect of ISO), then EV of settings A is +3 EV more than settings B (EV is the combination of shutter speed and f/stop settings). EV of A is greater (EV 18) because the 1/1000 shutter speed is faster, which is for less exposure of brighter light.

However Exposure Difference, if including ISO, then these two exposures are seen as Equivalent Exposures, because the higher ISO 800 of A compensates for its shutter speed. The EV 18 camera settings require +3 EV more ISO to be equal exposure of the EV 15 camera settings. Which of course it has that ISO here with ISO 800, so the exposures are seen Equal when adjusted to the same ISO 100 (EV100).

The Bottom Line at ISO100 shows 0 EV exposure difference (two equal exposures in this example).

There are more details about EV and LV on the EV chart next page.

Copyright © 2014-2017 by Wayne Fulton - All rights are reserved.