Exposure Simulator

http://www.andersenimages.com/tutorials/exposure-simulator/

by sneela • 5 months ago

139 81 5 months ago

That does a fairly good job.

I'm sure that image nerds would poke holes in it, but it seems to work pretty much exactly the way it does IRL.

The noise at high ISO is where it can get specific. Some manufacturers make cameras that actually do really well, at high ISO, and high shutter speed. This seems to reproduce a consumer DSLR.

arghwhat• 5 months ago

With the disclaimer that I am comparing to the memory of some entry-level cameras, I would still say that it's way too noisy.

Even on old, entry-level APS-C cameras, ISO1600 is normally very usable. What is rendered here at ISO1600 feels more like the "get the picture at any cost" levels of ISO, which on those limited cameras would be something like ISO6400+.

Heck, the original pictures (there is one for each aperture setting) are taken at ISO640 (Canon EOS 5D MarkII at 67mm)!

(Granted, many are too allergic to noise and end up missing a picture instead of just taking the noisy one which is a shame, but that's another story entirely.)

einr• 5 months ago

Noise depends a lot on the actual amount of light hitting the sensor per unit of time, which is not really a part of the simulation here. ISO 1600 has been quite usable in daylight for a very long time; at night it's a somewhat different story.

The amount and appearance of noise also heavily depends on whether you're looking at a RAW image before noise processing or a cooked JPEG. Noise reduction is really good these days but you might be surprised by what files from even a modern camera look like before any processing.

That said, I do think the simulation here exaggerates the effect of noise for clarity. (It also appears to be about six years old.)

ChrisMarshallNY4• 5 months ago

Yeah, I don't think that it's easy to reproduce noise (if it was, noise reduction would be even better). Also, bokeh/depth of field. That's not so easy to reproduce (although AI may change that).

1e1a3• 5 months ago

Video showcasing ISO noise behavior of a few different cameras: https://youtu.be/iiMfAmWbWSg?t=94s

ChrisMarshallNY4• 5 months ago

That's a pretty good demo!

Very limited camera choices, though.

nayuki4• 5 months ago

Excellent presentation and explanation. I agree with ~90% of it except the small part at 4m54s where he tries to give an answer about the existence of noise. Yes, sensor readout noise and A/D quantization noise exist, but he forgot the big elephant in the room: photon shot noise ( https://en.wikipedia.org/wiki/Shot_noise ). Light is inherently quantum mechanical, and the lower the brightness of a scene, the more that the discrete nature of light shows up in captured images.

Lately I've been researching cameras for astronomy, especially for deep-sky objects (DSOs) like nebulae that require hours of exposure time. The marketing material for these cameras go into a lot of detail: quantum efficiency (the percent chance that a photon converts into an electron), dark noise at different temperatures (fractions of electrons per second), readout noise (usually around 1 electron), and well depth (usually around 10k electrons). Compared to general photography, the astro community much more motivated to explain and keep track of all the sources of noise. Random product example: https://www.zwoastro.com/product/asi585mc-mm-pro/

sneela2• 5 months ago

I recently bought a film camera (Minolta X-700) and I wasted a whole roll because I inverted the aperture (i.e, 2 = sharp, 32 = blur)...

I'm interested to see how the roll turns out - gave it for development the other day, had a good laugh with the employees though.

I now have a mnemonic for it: Blor - a (somewhat) portmanteau of Blur and low. So low aperture = blur.

Edit for clarification: I mean low number (2 vs 32) = blur

4gotunameagain• 5 months ago

The larger the entrance pupil is, the narrower the depth of field is.

The smaller, i.e. the closest to an ideal pinhole camera, the wider the depth of field is. A an ideal pinhole camera has infinite depth of field.

Unfortunately the aperture f numbers are the wrong way round; larger numbers correspond to smaller diameters.

tiagod• 5 months ago

High aperture = Blur

Unfortunately the lower number actually means bigger aperture.

Toutouxc4• 5 months ago

Note that both very high or very low aperture settings also bring their own optical issues. At very low values (big hole) you’re getting hurt by different aberrations (essentially too many paths the same rays can take to the sensor) and at very high values you’re getting hurt by diffraction. At the low end, it’s good to go a little higher than the lens advertises, and at the high end anything over F13-F18 (depending on the gear) is usually quite bad.

JKCalhoun• 5 months ago

I think it is excellent as well—that it also demonstrates aperture and shutter priority is a bonus.

I do feel (image nerding now) that its shutter/ISO visual for showing the image over/under-exposed is not quite correct. It appears they show incorrect exposure by taking the "correct" image and blend (multiply) with either white or blend with black (on the other end of the exposure spectrum) to produce the resulting image.

I suppose I am expecting something more like "levels" that pushes all the pixels to white (or black) until they are forced to clip. (But maybe I am too trained in photo-editing tools and expect the film to behave in the same way.)

kqr3• 5 months ago

No, you're correct. I would have expected the highlights to blow out much sooner (for digital) and the shadows to block up much sooner (for analogue). The simulation doesn't portray this accurately, but it gives the general idea!

turnsout• 5 months ago

It needs to be updated to do its calculations in linear light, but it's probably useful for getting an intuitive sense of what the different levers of photography do to an image.

zokier• 5 months ago

Camera ISO and noise can be really complicated and even contentious topic. One complication is that some cameras are "ISO invariant" and on those cameras afaik it is beneficial to stick to the one or two native ISO values. There is also the whole discussion around ETTR etc

1e1a3• 5 months ago

Changing the ISO appears to scale the noise differently from the rest of the image.

dahart2• 5 months ago

Yep, just like a real camera.

ggambetta• 5 months ago

Nice, but I'm going to need some ND filters :)

pimlottc• 5 months ago

It seems to be impossible to grab the sliders on mobile Safari

dahart2• 5 months ago

Try tapping on the target value

trimaster• 5 months ago

Not sure why value on the exposure compensation scale changes in manual mode when ISO is fixed. Shouldn't it be static in that case, unless ISO was in auto?

czpl• 5 months ago

That's a light meter, not exposure compensation.

cratermoon• 5 months ago

This is missing a setting for the kind of light falling on the subject. Is it full open sunlight? Open shade? Overcast? Sidelight? Backlight?

It all matters.

PetitPrince2• 5 months ago

For me it's missing something to illustrate the relationship between shutter speed and motion blur. If the subject was a running fan instead of of lightbulb that would have been ideal.

moon26• 5 months ago

From the website:

If I ever find a good moving prop like a small fan, maybe I'll also re-shoot new previews to demonstrate how shutter speed affects moving objects.

Now, I'm just not sure how would one simulate a running fan with a picture. While for a static image you can have separated foreground and background and then apply effects for simulation (I know iPhone HEIC images have this property), for moving images you have to simulate the blur and the stillness, which is probably more difficult in terms of coding.

andyfilms1• 5 months ago

I love the idea that this guy was easily able to scrounge up a florescent bulb in a beer coozie, but a desk fan is somehow unobtainable.

nomel3• 5 months ago

Why simulate? Most modern cameras can be controlled through USB. Just actually take each one (except for ISO, which you can easily fake), encode the frames in a reasonable bitrate MP4, then have a lookup for the frame in the video. :D

PetitPrince2• 5 months ago

Ah ! Guilty as charged in not reading the whole page.

Now, I'm just not sure how would one simulate a running fan with a picture.

I don't think it's necessary for this app. This is simulating what the camera sees, not what our eyes can see.

erghjunk• 5 months ago

that's an insane amount of noise at 200 ISO.

10729287• 5 months ago

Probably Foveon sensor.

semiquaver• 5 months ago

I know that modern systems like aperture priority or full auto make things easier, but I maintain that the many photos I took with a fully manual film camera (Canon AE-1) were simply better than those taken with any subsequent DSLR. The simple act of calibrating the shutter speed, aperture size, and manual focus before and during shooting helps you slow down and think about composition and framing, making the end result more valuable. Same goes for the limited number of shots on a roll of film.

Nowadays it’s easier to just take lots of shots and fiddle with the setting and do bracketing and such. But I maintain something important was lost by the move to automatic cameras.

mmh0000• 5 months ago

Don't worry! We're moving away from automatic cameras, too. Soon, you'll just use ChatGPT to generate your vacation images on demand.

I'm being a little hyperbolic, but it really seems like, for a non-insignificant portion of the population, that will be true.

blacklion• 5 months ago

Friend of mine suggested "vacation camera" concept when Panoramio was established (around 2006): box with compass, GPS and Internet connection. You point it to the sight, press button, it downloads photos of this sight. If you have premium subscription, it downloads professional photos with professional post-processing.

Inserting user's mates was a problem in 2006.

sixothree• 5 months ago

The rate at which people are currently posting AI enhanced or modified images of themselves is a bit surprising to me. Apparently people very much like wearing different outfits or travelling to new places without actually having to put them on or actually leave the house.

moon26• 5 months ago

That's why I love fiddling with analog cameras for a bit, or even experimenting with old lens on newer DSLRs. I have a Canon Rebel from 2011 and sometimes love to use my soviet Zenit Helios 44M lens in it. I do have the Zenit which came with this lens, but I have yet to develop its film.

RankingMember• 5 months ago

I've started fiddling with an old Canon 30D again just because it's completely devoid of all the automatic post-processing I've become so used to with my phone camera. It's nice to just see the image as it is.

asdff4• 5 months ago

I used to have an old rebel xti, how do you actually confirm focus shooting like this? as far as I remember there were no aids for manual focus like film slr ground glass or modern mirrorless live view focus peaking.

caseyohara3• 5 months ago

Same goes for the limited number of shots on a roll of film.

You can approximate the same limitation on digital cameras by simply using a very small SD card.

kqr3• 5 months ago

Or put a large file on a regular size SD card.

jacobgkau• 5 months ago

Approximate, sure, although you can still go back and delete photos from a small SD card, whereas film's more of a consumable resource.

asdff4• 5 months ago

Even today you are better off shooting manually once you have metered the scene.

Otherwise your meter will pick up on color differences in a given framing and meter slightly differently. Shots will be 1/30th of a second, 1/25th of a second, then thanks to the freedom of aperture priority you might get little weird 1/32ths of a second you don't have discretely on a dial. How about iso. same thing, one shot iso 200, another iso 250, 275 this other one. Oh this one went up to iso 800 and the meter cut the shutter speed. Aperture too. This one f2 this one f4 this other one f2.5. This wasn't such a big deal even in the full auto film era since 35mm film has such latitude where you can't really tell a couple stops over or underexposed.

All these shots, ever so slightly different from one another even if the lighting of the scene didn't really change.

Why does this matter? Batch processing. If I shot them all at same iso, same shutter speed, same aperture, and I know the lighting didn't really change over that series of shots, I can just edit one image if needed and carry the settings over to batch process the entire set of shots.

If they were all slightly different that strategy would not work so well. Shots would have to be edited individually or "gasp" full auto button which might deviate from what I had in mind. Plus there are qualitative trade offs too when one balances exposure via shutter speed, vs via aperture, vs via iso.

omoikane• 5 months ago

I agree with slowing down and taking my time if I am shooting something static, but if I am outdoors taking pictures of anything that moves (e.g. birds), I am going to shoot in full auto burst mode until the buffer/SD card is full.

I understand I am relying more on luck and not being as deliberate with composition when I do that, and I have high respect for people who are able to get great wildlife photos with film. But for amateurs like me, it's far easier to get better pictures simply by taking more pictures.

gyomu• 5 months ago

Yeah, digital is just a game changer for wildlife photography, especially when considering the extremely fast smart autofocus / high shooting frame rates / top tier stabilization modern systems have.

“It was night and day. Six minutes instead of six years tells the story,” McFadyen says. “Instead of 12 frames per second, I can now shoot at 30 frames per second, so when a bird dives at 30 miles per hour, it makes it so much more likely you’ll capture it at the right moment.

McFadyen says that the focusing system is also “incredibly fast” on mirrorless cameras. “It can lock on the kingfisher’s tiny eye at these super-fast speeds,” he adds.”

https://petapixel.com/2025/11/27/photographer-recreates-king...

This is a bit of a marketing puff piece, but the core insights are correct - the kind of shots the photographer is talking about here were insanely hard to pull off on film, still very tricky to achieve with digital bodies in the 2010s - but modern tech makes them almost trivial.

geraldmcboing• 5 months ago

One thing that is lost when using auto cameras is using focus & DOF as part of composition. With an auto-everything camera, the only part the user does is frame the shot. But composing requires thought about where you choose to place the focal plane, and the depth of field. Also lost with auto digital is pre-visualisation. No need for it as most people just bang off shots & look at the result. The delay of seeing film developed means film prohotographers learn to previz their shots. Less and better.

shakow2• 5 months ago

One thing that is lost when using auto cameras is using focus & DOF as part of composition

That's why virtually all cameras have aperture-priority though, right?

Wolfbeta• 5 months ago

You're romantacizing the tinkering, but you're absolutely right.

That friction of adjusting machinary to capture what we felt against what we saw was part of the process.

It slowed us down just long enough to appreciate the patterns, the textures, the form, the haesscity of a moment that seized our attention.

moon26• 5 months ago

This is honestly the best and most simple way to learn photography, at least something basic that is still very hard to grasp sometimes. I know photography is not just about the photometer, and about depth of field, but this simple simulator helps to learn about these relationships between aperture size, shutter speed and ISO which always bugged me (sometimes my shots were bad and sometimes great).

agos• 5 months ago

this is a cool idea, but not very well executed. it appears it just overlays white on top of anything? exposure does not work this way

Toutouxc4• 5 months ago

image "noise" or "grain" that is introduced into a picture as you increase the ISO

Not this absolute shit again. This is not how photography works or how physics actually work. Image noise does NOT come from high ISO, it comes from low exposure (not enough light hitting the sensor). ISO is just a multiplier between a number of photons and the brigthness of a pixel in your photo. The implementation of the multiplier is (usually) half-analog and half-digital, but it's still just a multiplier. If you keep the exposure the same, then changing the ISO on a digital camera will NOT introduce any more noise (except for at the extremes of the range, where, for example, analog readout noise may play a role).

This "simulator" artificially adds noise based on the ISO value, as you can easily discover: Set your shutter to 1/500 and your aperture to F8, then switch between ISO 50 and ISO 1600 and look at the letters on the bulb. ISO 50, dark but perfectly readable. ISO 1600, garbled mess. Since the amount of light hitting the simulated sensor stays the same, you should be seeing slightly LESS noise at ISO 1600 (better signal to noise ratio than at low ISO), not more.

edit: To add something genuinely useful: Use whatever mode suits you (manual, Av, Tv) and just use Auto ISO. Expose for the artistic intent and get as much light in as possible (i.e. use a slower shutter speed unless you need to go faster, use a wider aperture unless you need a narrower one). That’s the light that you have, period. Let the camera choose a multiplier (ISO) that will result in a sane brightness range in your JPEG or RAW (you’ll tweak that anyway in post). If the photo ends up too noisy, sorry but there was not enough light.

ISO is an almost useless concept carried over from film cameras where you had to choose, buy and load your brightness multiplier into the camera. Digital cameras can do that on the fly and there’s usually no reason not to let them. (If you can come up with a reason, you probably don’t need this explanation)

shakow2• 5 months ago

If you keep the exposure the same, then changing the ISO on a digital camera will NOT introduce any more noise

So does this mean that changin the ISO directly on my camera, or in DarkTable/whatever at post-proc time is virtually the same?

nayuki4• 5 months ago

If you have an ISO-invariant camera, then yes - the final image would look the same whether you shot at low ISO and raised it in post versus shooting at a high ISO and doing no further editing. You can try it yourself. Or you can read the numerous reviewers who have already done that in the past decade, such as DPReview.

Toutouxc4• 5 months ago

Yes, as the sibling post says, it's effectively the same in most cameras and it's exactly the same in certain cameras (not many). Unless you, of course, actively fuck up by shooting a very low-exposure (dark) shot with low ISO (then you lose precision, because your analog measurements get quantified into small integers, that are also close to the noise floor), or by shooting a very bright shot with high ISO (where your highlights get multiplied right out of the range of your output format). If you don't actively try and fuck up the shot (AND you shoot RAW), you can make pretty wild changes in post and the data will be there.

That's just one more reason not to be afraid of auto ISO. The camera will choose something sane and you'll have ample room on both sides to get the image you wanted.

gruez• 5 months ago

Image noise does NOT come from high ISO, it comes from low exposure [...] changing the ISO on a digital camera will NOT introduce any more noise (except for at the extremes of the range, where, for example, analog readout noise may play a role).

Sounds like you're saying that setting higher ISO does cause noise, but as long as you don't go too high you won't really notice the difference?

internetter2• 5 months ago

No. What they're saying is ISO multiplies brightness, essentially exasperating differences. Roughly, ISO 200 is 2x gain and so on. So if you have one pixel with a brightness value of 1, and the pixel to the left has a brightness of 5, and an ISO of 500, then it becomes brightness 5 and 25 respectively. Oversimplification.

nayuki4• 5 months ago

Agreed. In other words, ISO is not exposure. Exposure is purely about how much light arrives on the sensor - which is a combination of scene illumination, object reflectivity, relative aperture, and shutter speed. ISO only plays a part in controlling how bright the output image is.

bibimsz4• 5 months ago

ISO does not create noise. It amplifies (accentuates) the noise that is already there.

thot_experiment• 5 months ago

kinda lame to use "brightness" as an analog for exposure, they're really not the same thing, at the very least do the transformation in a deeper color space before displaying it to the screen, the source images almost certainly have more than the 8 bits being used here

xp84• 5 months ago

Note! The exposure portion of this simulator currently does NOT work with Internet Explorer!

Don't tell me what to do!

Bimos• 5 months ago

I like the fact that the photos seem to be real rather than simulated.

sirto• 5 months ago

I would like to add to the discussion my mod of Tim's work (with the author's permission) for astrophotography: https://paolo.sirtoli.it/astrophoto.html

Every photographer knows very well the exposure triangle: shutter speed, aperture and ISO, but in astronomy usually only aperture and focal ratio are considered. So I added a third dimension to illustrate the basic triad of astrophotography: telescope aperture, focal ratio and image resolution.

bibimsz4• 5 months ago

hdr cinema setting: shutter: one click right of 1/60 fstop: one click right of f11 iso: one click left of 100

bibimsz4• 5 months ago

or maybe: ss: one right of 1/550, fs: f/4, iso: 100

bibimsz4• 5 months ago

I found this quite fun! Thanks for going through the effort!

Exposure Simulator

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