aperture and sensor size

goodguy1206 · Oct 4, 2015

Hi All,
I keep asking myself a question about the aperture.
I currently have a compact that open at f/2.8,
I found that it's very limited when it's getting darker (typically in my living room at night),
even with the ISO level at 1600, open at 2.8, it typically needs 1/40s to take a shot, and it's getting blurry as soon as the subject is moving slightly.

Although I feel that changing camera for a APS-C will help,
I can't find the technical reason,
as at the same ISO, same light (inside my living room), and same aperture (2.8), the picture speed will be the same ? right ?

I'm trying to find a solution that does not involve using the flash,
so it is worth changing camera ?

Thanks for you help

jaomul · Oct 4, 2015

At same aperture , with same iso exposure should be the same irrelevant of sensor size. If I am wrong (which is possible) I am misunderstanding something I believe to be true for a long time

goodguy1206 · Oct 4, 2015

hm, so what's the trick ?
using the flash : don't really want
increasing the light in my living room: ok but then I can't do that in a church or in my friends living room.
increasing the ISO: getting noiser,
decreasing speed: image getting underexposed,
how do you guys do in these situations ?

jaomul · Oct 4, 2015

I'll take noise over blur anyday. Also if you increase iso and its properly exposed the chances are you'll have less noise than an underexposed shot at less iso

SCraig · Oct 4, 2015

Regardless of the camera you have four choices. You can pick one or any combination of the four:
1. Decrease shutter speed.
2. Open the aperture more.
3. Increase the ISO.
4. Increase the amount of light on the subject.

No matter how much we wish it were otherwise those are the only four choices.

Ysarex · Oct 4, 2015

goodguy1206 said:
Hi All,
I keep asking myself a question about the aperture.
I currently have a compact that open at f/2.8,
I found that it's very limited when it's getting darker (typically in my living room at night),
even with the ISO level at 1600, open at 2.8, it typically needs 1/40s to take a shot, and it's getting blurry as soon as the subject is moving slightly.

Although I feel that changing camera for a APS-C will help,
I can't find the technical reason,
as at the same ISO, same light (inside my living room), and same aperture (2.8), the picture speed will be the same ? right ?

Right. Exposure is a function of shutter speed + f/stop + available light regardless of sensor size. So with low available light you're going to get the same f/stop and shutter combination with any camera.

goodguy1206 said:
I'm trying to find a solution that does not involve using the flash,
so it is worth changing camera ?

Thanks for you help

You can improve your results by changing cameras. You need either or both:
1. A lens that opens to a wider aperture.
2. A larger sensor will render a better result in the low light condition you're experiencing. That means you can underexpose the sensor more (raise ISO) and still get a serviceable photo.

Joe

TCampbell · Oct 4, 2015

The aperture is described as a "focal ratio". It's a ratio of the length of the lens divided by the physical diameter of the lens' aperture opening. Because it uses a "ratio" it works as a measure of light gathering capability of a lens regardless of lens size or sensor size.

In other words... pick any combination of exposure settings... ISO 400, f/2.8 and 1/100th of a second. That combination will yield the SAME amount of light on the image sensor REGARDLESS of what camera or lens was used to capture the shot.

What a DSLR will give you is the ability to change the lens. So... suppose instead of that f/2.8 lens, you used a 50mm f/1.4 lens (the lens alone would probably cost around $400 new). But that lens has a focal ratio which allows for literally four times more light collection than f/2.8.

That means... that if you had such a lens on a camera using ISO 1600, then instead of 1/40th sec shutter speed, you would be able to shoot at 1/160th sec shutter speed. You can see how that would make a big difference.

Alas, there is no "free lunch". While the lower focal ratio lens collects more light, it also has a much shallower depth of field (range of distances at which your subject will appear to be reasonably focused.) This means if you are photographing a "group" in this lighting, you probably won't be able to get everyone in the group in sharp focus. But if you shoot an individual person, you can certain make sure their eyes and face are focused -- even if nearer or farther objects in the room are blurred.

But if you buy a DSLR with the "kit" lens (typically an 18-55mm f/3.5-5.6 zoom) then the light gathering capability of that lens will actually be worse then the camera you have now.

Something that should never be forgotten... is that there's a strong probability that you can fix the situation by changing the environment where you are shooting your subject... switch on a light... ask the subject to move over to a location where the light is better.

When I shot professionally, I rearranged furniture ALL THE TIME to create a scene with better lighting than the room naturally had if I left the furniture where I found it (yes... I put it back after the shoot.)

goodguy1206 · Oct 4, 2015

thanks a lot everyone for these detailed answers,
it makes full sense, and will save me some investment in the wrong type of material.
have a nice day

Braineack · Oct 4, 2015

goodguy1206 said:
hm, so what's the trick ?
using the flash : don't really want
increasing the light in my living room: ok but then I can't do that in a church or in my friends living room.
increasing the ISO: getting noiser,
decreasing speed: image getting underexposed,
how do you guys do in these situations ?

we do what you really don't want to.

480sparky · Oct 4, 2015

TCampbell said:
The aperture is described as a "focal ratio". It's a ratio of the length of the lens divided by the physical diameter of the lens' aperture opening. Because it uses a "ratio" it works as a measure of light gathering capability of a lens regardless of lens size or sensor size..............

Correct. Aperture is not a single measurement of the blade opening, it is half of a fraction. The other half is the FL of the lens.

soufiej · Oct 4, 2015

(Said with a John Wayne twang ... )

"Hold on there, pardner!!!

Take one step back and no one will get hurt.

Now, drop the search engine.

That's it, now kick it over here.

Nice and gentle like!

Good, now we can talk."

You are, IMO, teetering on the brink of a cliff known as "If only I had better gear". There's a slippery slope at the edge and, if you hit it, you'll go down to the very depths of Dante's fourth circle.

The good news is you are basically correct when thinking a camera with a larger sensor and a lens with a "faster" aperture will allow lower shutter speeds and/or lower ISO values. Though, as TC indicates, if your information comes from reading the internet, this is following a somewhat untrustworthy prophet. The trick prophets use is to include just a smattering of truth and then to lie their rear ends off once you begin believing they are there to help you.

So ... drop the prophet.

Kick it over here.

Good.

One of the first things to realize is, everything and anything you buy will be a trade off. No matter what you buy, there will be a drawback to owning that product.

This applies to pretty much everything you can buy, not just cameras.

Certainly, cost is one of the most significant issues when you begin asking for a camera with better low light performance. Incremental improvements can cost exponential amounts.

Other considerations of overall image quality and ease of use, say, when needed to catch that quickly developing shot, can and probably should enter the picture.

Once you begin thinking new gear is the answer, you tend to get caught up in the web of always thinking more and better gear will be the answer. The pattern then begins where you acquire gear until you either become frustrated by the basic rule that says you must ultimately live with the limitations of whatever you own or you realize everything is a trade off to begin with.

Once you reach that point - or, hopefully, long before - you must realize the first rule of photography is you need light. The more light you have available to you, the better you will be at taking good photos. More available light means more available options for you, the photographer. If natural light is limited, you need to reduce your list of options and select the most appropriate next best response.

You do not state a reason for not wanting to use flash as a supplement to the available light but this is somewhat irrational once you consider the fact every camera you can buy is still a trade off.

Yes, you can gain faster shutter speeds and lower the ISO value by buying a "better" camera. However, given the virtually constant reductions in available light once you step indoors with your camera, eventually you will find the best next step is to rely on flash as a supplement to your camera's light gathering capacity.

The question then becomes which is the next best option in flash units. Because, if you are not using a flash and you want supplemental light, then your cost again begins to climb. Add to this the fact flash can, for most average photographers, be more flexible in its application than would be fixed lighting fixtures and you find some very good reasons to begin looking at flash units.

Of course you can do better with a camera that is superior in technical measurements to your compact. However, once you begin to think you will be better once the gear is better, the chances of you heading down a very dark and dangerous path increase.

It is far less expensive, and generally considered to be the smarter option, to add supplemental light than it is to just buy more camera. Gear heads, of course, disagree with that statement.

If flash would somehow disturb your subject - a child perhaps - then you should investigate other means of setting up your shot. Or, realize everything has its limits and work to discover your next best work around. High ISO values can be resolved in several ways, most of them done in post production. Some cameras offer better than average high ISO performance but they too have their drawbacks; Fuji X100T Review

That's my opinion at least. I'd say buy a better camera, it will be an investment you do not regret if you purchase wisely. Do not, however, begin to think the gear makes the photograph.

SL1 alternative for better IQ at high ISO?: Canon Rebel (EOS 1200D-300D) Talk Forum: Digital Photography Review

Ido · Oct 4, 2015

By simply increasing the sensor size, and keeping all Exposure Triangle settings unchanged, you won’t get a brighter image. The reason to ever choose a larger sensor, though, is to be able to use higher ISO settings for the same “quality.” (Of course there are other advantages, but they are irrelevant to your question.)

Derrel · Oct 4, 2015

goodguy1206 said:
Hi All,
I keep asking myself a question about the aperture.
I currently have a compact that open at f/2.8,
I found that it's very limited when it's getting darker (typically in my living room at night),
even with the ISO level at 1600, open at 2.8, it typically needs 1/40s to take a shot, and it's getting blurry as soon as the subject is moving slightly.

Although I feel that changing camera for a APS-C will help,
I can't find the technical reason,
as at the same ISO, same light (inside my living room), and same aperture (2.8), the picture speed will be the same ? right ?

I'm trying to find a solution that does not involve using the flash,
so it is worth changing camera ?

Thanks for you help

Yeah...a camera with a much larger and a much better performing sensor would make it much easier to get decent photos in marginal light. The newest sensors made by Sony, and used in Sony, Pentax, and Nikon d-slr cameras, have the ability to allow software push-processing of images that have been deliberately under-exposed in the field--by three, four, and even five full f/stops or five full shutter speeds. This is something that has kind of developed since the mid-2000's part of the decade. dPreview is now calling cameras that allow this 3,4,5 EV push-processing "ISO invariant". The Nikon D7200 is the camera they have identified as the best one they have ever tested as far as its ISO invariance capability. The Nikon D810 and the Sony A7R II are also superb in terms of ISO invariance. The Canon 1Dx is quite good too.

Basically, the idea is that, using these latest, top-performing sensors, it's possible to shoot photos at faster shutter speeds, or smaller lens openings than would normally be required; this results in a VERY dark,dark image on the camera; the raw image file is then opened in a raw converter software application, like Adobe Camera Raw, Lightroom, CaptureOne, and so on; the image is then "brightened up" using the software. Now, tis used to result in terrible images, filled with banding and or noise, and very weak color, but the newer sensors made by Sony, particularly Sony, but also to an extend the ones made by Toshiba, allow pretty good images quality to be maintained.

You need to remember though that low light is often rather unappealing light, and might very well have light placement that gives people raccoon eyes, and so on. But yes, bigger, better, new-generation sensors have the ability to give much better low-light performance than what compact cameras can accomplish.

KmH · Oct 4, 2015

Look at the specifications for the lens on your compact.

It likely say that f/2.8 is an equivalent f-stop and the actual f/x is something different.

Ido · Oct 5, 2015

KmH said:
Look at the specifications for the lens on your compact.

It likely say that f/2.8 is an equivalent f-stop and the actual f/x is something different.

They don’t do that for aperture, only for focal length. If they did do it for the aperture, people would think it affects their exposure settings (it doesn’t, unless the manufacturer also tweaked how the ISO numbers work), or they would see something like f/16 as the maximum aperture and nobody would buy it.