Low light photography, auto ISO and faster lens f1.4 or f1.8

[Nathaniel]

I have been using my Canon 6D with the 24-105mm f4 lens with auto ISO,manual TV 160,f6.5- f8 (depending),auto WB for low light photography in the Cathedral and the results have been OK (see my posts elsewhere on the forum). However, I find that using the f4 lens the auto ISO goes up to 12,800 without of course showing any visible noise. Am I right in my assumption that if I use a faster lens say either f1.8 or f1.4 will bring down the auto ISO to less than 12,800 (at the moment) with the same exif given above ie TV 160,f6.5-f8 etc?

Thank you.

Nat

[planetc]

Re: Low light photography, auto ISO and faster lens f1.4 or f1.8

Won't make a blind bit of difference if you are stopping it down to f6.5 or smaller anyway Nathaniel. I would open that aperture up if you need more light

[Tigger]

Re: Low light photography, auto ISO and faster lens f1.4 or f1.8

However, I find that using the f4 lens the auto ISO goes up to 12,800 without of course showing any visible noise.
Nat

so whats the issue ? if your combination is working fine then why try to lower the ISO - I know your photos Nat and I don't see anything wrong with them for what they are, which is a good record of the event! Also you have to take into account going for a faster lens does mean you'll loose the flexibility that the 24-105 offers you

As Paul pointed out if your going to close it down theres no benefit and in fact could be worse off as you won't have the zoom option the 24/105 will offer

[Nathaniel]

Re: Low light photography, auto ISO and faster lens f1.4 or f1.8

Thanks Paul and Ian for your good advice. Yes, I love my 24-105 lens. However,as I am still trying to understand the rationale of ISO, I might continue with a few more foolish question with apologies. I must mention that this thread borders on my contemplating a 85mm f1.8 lens prime for a better reach and maybe a bit more sharper pics. Getting back to the thread, what then is the real advantage of using a faster lens in low light situations? Has the problem of low light, flashless photography,disappeared with the advent of the 6D,5Dmk3 and similar.

[Paulstw]

Re: Low light photography, auto ISO and faster lens f1.4 or f1.8

The 85 1.8 will really only achieve a better focus grab. Stopping down to 5.6 while increasing the DOF, won't help with the exposure. I think the best idea is a ultra wide angle fast aperture. It manages to open up that DOF and you can still use the 2.8 aperture. The fall off is that people can often look distorted on the edges. The DOF on an 85 1.8 @ 1.8 would be quite thin I think. Not sure.

[Tigger]

Re: Low light photography, auto ISO and faster lens f1.4 or f1.8

The 85 1.8 will really only achieve a better focus grab. Stopping down to 5.6 while increasing the DOF, won't help with the exposure. I think the best idea is a ultra wide angle fast aperture. It manages to open up that DOF and you can still use the 2.8 aperture. The fall off is that people can often look distorted on the edges. The DOF on an 85 1.8 @ 1.8 would be quite thin I think. Not sure.

agree and not ideal when doing reportage photos

[planetc]

Re: Low light photography, auto ISO and faster lens f1.4 or f1.8

The advantage for you of the higher iso is that you can shoot with a smaller aperture and maintain a reasonable depth of field. As has been said, I think the 85 1.8 will have a very tight dof when you take advantage of the wider aperture. I looked at the same lens as an option for me. The thing to remember is that the faster lens is only faster if you are using it wide open, which may not fit your needs.

[Robert Scott]

Re: Low light photography, auto ISO and faster lens f1.4 or f1.8

...what then is the real advantage of using a faster lens in low light situations?.

With an optical viewfinder the image is usually formed at the maximum aperture of the lens. So one advantage of a faster lens is a brighter viewfinder image - useful in low light.

[ColytonJohn]

Re: Low light photography, auto ISO and faster lens f1.4 or f1.8

Nat,

All increasing ISO does is make the sensor more sensitive to light enabling a narrower aperture and/or a faster shutter speed but, and this is the BIG but, increasing ISO introduces noise (grain) and not all cameras are as well behaved as other when it comes to how intrusive it is. The 6D (and seemingly the 7D2) are excellent while many others such as my 7D and, ahem, your 100D are poor.

Keeping the ISO low to avoid noise means you then have to open up the aperture and/or slow the shutter speed both of which can have a detrimental impact on the photographers intentions (reduced DoF or motion blur/camera shake).

This may help understand the 'Exposure Triangle': http://www.messersmith.name/wordpres...sure-triangle/

The 85mm f1.8 we were talking about was to help with the poor ISO performance of the 100D and, while using it at f1.8 will bring the ISO down, it will also narrow the depth of field probably to the point where you'll get lots of lovely blurry bokeh behind the bishop's head and I suspect that's not what you or he want.

For your church interior photography then your 6D and 24-105 will be about as good a combination as you can get.

Cheers,
John

[Paulstw]

Re: Low light photography, auto ISO and faster lens f1.4 or f1.8

One thing to add to this is the fact that at high ISO's you are really destroying the colour reproduction. Yes you can raise the vibrancy or saturation but it invariably ends in a mushy mess. I agree with John. A wide aperture lens at distance can yield a great result for single portraits. Just not great for a group of folk sitting at different levels to the sensor.

[kelly200269]

Re: Low light photography, auto ISO and faster lens f1.4 or f1.8

Not to confuse the issue Nat, but looking at your photos, there are many shots of people and groups. For these shots, at relatively close quarters in a church, the 85mm would be impractical, as you would struggle to get everything in the frame.
If you were after more light to keep the ISO down, then the 28mm f/1.8 or the relatively new 35mm f/2 IS might be the best options. They are both wide-angle, but at 2 or more stops faster than your zoom, they both 4x more light in. You could then crop for detailed shots if you wished, which wouldn't pose a problem at all with the 6D.
IMHO the 35mm is probably the best solution.
PS - I'm not advocating buying more gear for the sake of it, as you should always learn to use what you have and be aware of its limitations before splurging on something else, but the fact of the matter is in low-light in dimly-lit venues such as churches, the 'limiting factor' in controlling exposure is f/4 aperture of your zoom. Once you find that this is limiting you, it is probably time to look for faster glass.

[Wayne Els]

Re: Low light photography, auto ISO and faster lens f1.4 or f1.8

Nat, I'd suggest you could try slowing the shutter quite a bit. 1/160th is really quite fast for static/slow moving stuff. I've not been in a church in a long time but unless things have changed and people are dancing about like the Blues Brothers I'd suggest trying speeds around 1/80. That should enable you to drop the ISO.
It might be better to set the ISO manually, I find auto ISO tends to pick at the extremes of it's range.
Paul makes a very good point about the shallow dof of a fast aperture too.

[Nathaniel]

Re: Low light photography, auto ISO and faster lens f1.4 or f1.8

Thank you folk for all your good advice. Quite a lot to take in but I will print it all out and read all your comments more slowly. One other point I should have mentioned is that (i) churches are increasingly being used for the acoustics and many concerts are being held in churches AND I have to cover 3 concerts in December. (ii) It is not often that I can get in close to the "area of action" and hence I have to keep to a distance- this is why I started using my 24-105mm in preference to the 50mm. (iii) the 85mm came into my thoughts because of the possibility of taking the pics from a distance and thought that the f1.8 would be better than the f4 of the 24-105.

I like Wayne Els idea of reducing the TV from 160 but wondered whether if this is reduced to say 125 keeping it just above the max 105mm of the lens it would reduced the ISO to what I would really like it to be. I also accept Kelly's point of the "limiting" point of f4 on my zoom.Very frankly I haven't yet taken any pics at f4 todate with say 5.6 being the widest I have opened up.

It is only when I move forwards in photography I find that I have so much more to LEARN AND UNDERSTAND.

[EOS_User]

Re: Low light photography, auto ISO and faster lens f1.4 or f1.8

Hi Nat;

As with all things in photography, there are multiple ways of achieving what you want, but most involve a compromise of one form or another!

E.g; reducing Tv to 1/125 will help (marginally) reduce the ISO, but may in turn lead to camera shake; although the IS on the 24-105 will help. It depends how steady you are. Some can hand-hold down to 1/25 easily; others need 1/250!

If the high ISO on your 6D is giving good results I'd use it to its potential. That will enable you to use a smaller Av for better DoF, and a faster Tv to avoid camera shake or movement blur.

There is a handy online DoF calculator here that you can play with to see what differences focal length, f-stop and distance from subject make to the results.

E.g; At 105mm, f/4 and 15 feet from subject, you get a DoF of 1.5ft. At 85mm, f/4 and 12 feet from subject (you need to be closer to achieve the same Field of View) you get a DoF of 1.4ft! So nothing in it really!

The 85mm lens will only help if you need to open the aperture greater than f/4, but in doing so you will reduce DoF. At f/2.8, 85mm and 12ft, the DoF reduces to 1.0ft!

And so it goes...

Good luck...

[Bhuna]

Re: Low light photography, auto ISO and faster lens f1.4 or f1.8

Have a look at your metadata to see what focal length you are mainly shooting at from the position you are normally at in the church to make sure that 85mm (if you chose that lens) isn't too close now to take pictures at as you won't have the variable length.

Also re switching down TV you mention remaining above the focal length of 105 max just in case but remember you have IS so could come down to just below it by 1 or 2 stops.

Finally sorry to hijack with a question but it's on topic, does ISO stops work like Aperture and time stops, so if I wanted to stop 1 down from ISO 3200 to 1600 to reduce noise, could I compensate by decreasing shutter speed 1 stop or is ISO not stop related?