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01-03-2016, 12:27 PM   #1
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Low light - using wide aperture e.g. f1.8

Hi all

I've been enjoying learning about photography over the last few years and I now take photos at a soul music night in the city I live in. This has tested and progressed my skills and I thoroughly enjoy it (had good feedback too).

At the moment I use a flash, but I feel this is a bit intrusive and I'm considering getting a lens with a aperture of f1.8, such as the Sigma 18-35mm.

However, this raises a question in my head. I find focusing difficult - the light is really low and people are moving. I rely on manual focusing, but have to use Live View to be able to see when it's sharp (I don't particularly like that because of battery drain and a bit of a lag before the photo is taken). In order to give myself more leeway with DoF, I tend to shoot at a pretty narrow aperture.

I guess there are two questions:

- I know f1.8 lets in way more light. Will it be enough to use on a dimly lit dancefloor though? I would use the lens I other circumstances, but this would be the main use.

- the depth of field at f1.8 will be very shallow. Given it's hard to see when manual focusing, I imagine it'll be much harder to get the focusing correct. I worry this will negate any advantages of having this lens.

Any advice gratefully received!


Si

01-03-2016, 01:17 PM - 1 Like   #2
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An f1.4 or f1.2 lens is going to be much better for low light than an f1.8 lens.

You also say you shoot at a narrow aperture to help with DOF. If that is the case then the wider aperture lens is not going to help you at all in regards to low light except maybe for composition.

What lens(es) are you currently using?
01-03-2016, 01:27 PM - 1 Like   #3
Ole
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If you want to rely on autofocus the Sigma 18-35 F1.8 is not the way to go. Its AF is unreliable and so far no fix has been made available.

I don't know which focal length you need, but perhaps the hard to find but still available as new Pentax FA 35mm F2 would do the job? It is small and compact and fast.
01-03-2016, 01:33 PM   #4
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Thanks very much for the reply.

I just use the 18-55mm kit lens or my 18-250 travel zoom. They're the only lenses I have.

I only shoot at around 18-30mm, mostly 18mm.

Yes, I see what you are saying about the DoF. I'd certainly stop shooting at narrower apertures and exploit the f1.8 if I knew I could focus properly. I'm only using F8, F11 etc to give me more chance of getting things right.

Out of interest, I wonder how professionals shooting gigs, clubs etc get around this. I presume they are using lenses with very wide apertures. How would they focus, assuming the light is too low to auto-focus?

01-03-2016, 01:37 PM - 2 Likes   #5
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Concert photography is usually done without using flashes, similar to certain sports events. Even a F/1.4 lens won't allow you to use shutter speeds comparable to flash sync speeds. You'll have to raise ISO speed to your least acceptable values. DOF increases with shorter focal length & crop factors > 1. Shouldn't be much of an issue if you have the main artist in focus.
01-03-2016, 01:54 PM - 1 Like   #6
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Definitely get a larger aperture lens but also be prepared to shoot up to 3200 ISO assuming you have to capture movement.

While you are wise to shoot at lower apertures, generally one or two stops below maximum should give you a fair balance of depth of field and sharpness. Also under exposing by a stop is usually ok in RAW format. With club shots always expose for highlights to ensure you don't blow out whiter faces.

I aim for exposing most of my shots at F2.8 - F4 at between 1/60th to 1/125th sec and adjust ISO to accommodate.

The nice thing about digital is you can check the results for sharpness and exposure as you go.

Once you've got a decent pic I'd use a lot of multi-exposure shots to ensure you get the right image and delete the less useful pix as you go.

Learn a good noise reduction post processing technique so you can get the cleanest output from the session.
01-03-2016, 02:00 PM - 1 Like   #7
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QuoteOriginally posted by Popty Ping Quote
Thanks very much for the reply.

I just use the 18-55mm kit lens or my 18-250 travel zoom. They're the only lenses I have.

I only shoot at around 18-30mm, mostly 18mm.

Yes, I see what you are saying about the DoF. I'd certainly stop shooting at narrower apertures and exploit the f1.8 if I knew I could focus properly. I'm only using F8, F11 etc to give me more chance of getting things right.

Out of interest, I wonder how professionals shooting gigs, clubs etc get around this. I presume they are using lenses with very wide apertures. How would they focus, assuming the light is too low to auto-focus?
Many use full frame cameras and high ISO then they use noise reductio, software and possible downsampling to produce images.
01-03-2016, 02:21 PM - 1 Like   #8
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Remember that a fast lens also gives you a brighter viewfinder image, which can actually make critical manual focus easier in lowish light.

01-03-2016, 03:05 PM - 1 Like   #9
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I've been in similar situations and found the DA* 16-50 f2.8 to work well.
01-03-2016, 03:23 PM - 1 Like   #10
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I won't repeat what others have said but what body are you using? Reason I'm asking is that you noted you're using live-view and MF because AF is such a crapshoot. I found that my K-5 had real trouble focusing under artificial light, lots of hunting and really no telling whether the focus was right. I think the camera AF module had a bit of trouble.

This was definitely addressed in the K-5 II(s) and I now feel the camera is a lot more responsive and I'm willing to open up the aperture a lot more, trusting the AF to nail it. So if you haven't switched to the K-5 II(s) or K-3 (II) yet, consider that option. It will allow you to shoot at wider apertures and less DOF while still getting the subject sharp.

Then on to your lenses: the 18-55mm kit lens or my 18-250 travel zoom are really not made for the kind of environment you describe and they will hamper you all the way. Especially a superzoom is probably not very useful. If you're on a budget, try getting either the Tamron 17-50 or its Sigma counterpart, both are f2.8 and pretty sharp even wide-open under concert circumstances.

The truth is that for low-light mass-performances like concerts most people eventually end up shooting a camera such as Nikon's D750/810 or any of its Canon counterparts with a prime lens but that's a lot of cash to spend and you can move a lot from where you are now without going that far.

Having said that, if you often shoot at 18mm, possibly even the Ricoh GR might be the ticket for you, who knows? With a hell of a sharp 18.3mm f2.8 lens it could certainly do the trick.

Anyway, take a long, hard look at your body with a potentially not too expensive upgrade to the second-gen K-5 and get one of the nicely priced f2.8 wide 3rd-party zooms - it could just do the trick for you!
01-03-2016, 03:58 PM - 1 Like   #11
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If i may propose a different idea,

while the sigma 18-35/1.8 is a stellar lens, there seems to be a high degree of sample variation with focus-errors (thus you may have to also rely on MF there), also its quite an expensive option.

in your position, i would consider a fast 50mm like the FA/1.4 (it gets you the option to stand back a little) alongside the tamron 17-50/2.8. you can find those two used for much less than the sigma and it gives you more flexibility.

(in case you wish to go wider, i can recommend the pentax da 14/2.8, it has soso critics, but i find it especially fun for people photography in narrow spaces)

hope that helps
01-03-2016, 06:05 PM   #12
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Guys - this is fantastic info. Thanks so much.

I've been out and it's late here, so I won't reply properly now. Will do so properly tomorrow.
01-03-2016, 08:19 PM - 2 Likes   #13
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Looking at a depth of field calculator, at 18mm, f3.5 and 10 feet away, the range of in-focus subjects should be everything from about 6 feet to 27 feet away. I'd at least try the DA 18-55 wide open before buying the Sigma. You can gather some information by taking shots without a flash, even if they aren't usable. There will be a minimum shutter speed, just fast enough to freeze subject motion. The aperture controls depth of field and therefore what's enough in focus for you. Then see what ISO gives you a good exposure at those other two settings.Then you can figure out whether a different lens would work for you before buying it. If you have a shot that's bad and could have reduced depth of field, a faster lens could allow you to reduce ISO.
01-03-2016, 09:16 PM - 1 Like   #14
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QuoteOriginally posted by Ole Quote
If you want to rely on autofocus the Sigma 18-35 F1.8 is not the way to go.
Succinctly put.
01-03-2016, 11:18 PM - 1 Like   #15
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manual is the key here

I have used 1.8 lens in low light and there is low depth of field and you might have to manually focus.
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