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What focal lenght - aperture would you use in low light?
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PostPosted: Wed Oct 14, 2009 8:49 am    Post subject: What focal lenght - aperture would you use in low light? Reply with quote
I mean a situation you would have just one lens and had to shoot all kinds and sizes of objects. Not very dark but say normal day inside without flash.

I'm just thinking that 1.4 / 50 is not very usable if you shoot like a barrel or something and focus is only on the front side. Smile

Short or long is the question? Is 2.8 enough?


PostPosted: Wed Oct 14, 2009 9:23 am    Post subject: Re: What focal lenght - aperture would you use in low light? Reply with quote
kansalliskala wrote:
I mean a situation you would have just one lens and had to shoot all kinds and sizes of objects. Not very dark but say normal day inside without flash.
I'm just thinking that 1.4 / 50 is not very usable if you shoot like a barrel or something and focus is only on the front side. Smile


But may be useable for other situations. And for the barrel, you can stop the lens down. The reverse is not possible (make a f2.8 lens faster than it is when you could use thin DOF)

Quote:
Short or long is the question?


You can crop a short FL image into a detail. You can not enlarge a long FL image to show more. The answer is obvious. I always use my 1.4/35 Distagon for the situation you describe. 35mm is wide enough to get ambient, but not so wide that the small objects can't be satisfactorily enlarged by cropping, if needed.

Quote:
Is 2.8 enough?


No. There will be situations when you can use a f1.4 aperture and to have to use a f2.8 means to lose two stops, that usually means higher ISO and much more noise. A shot that you could make at ISO 400 with moderate noise, would become a ISO 1600 with high noise. This will make the difference between an image that is clear and can be printed in moderately large size, and an image that is noisy and can only be printed small.


PostPosted: Wed Oct 14, 2009 10:34 am    Post subject: Reply with quote
Rangefinder cam, between 50mm and 35mm lens, 1/30sec @f/2.8 for normal daytime indoors, if the lens allows, can go down to f/2 and 1/15 if needed. B&W ASA 400 film.

Or that's what's worked for me in the past


PostPosted: Wed Oct 14, 2009 12:35 pm    Post subject: Reply with quote
Here is a cool gadget:
http://www.dofmaster.com/dofjs.html


PostPosted: Wed Oct 14, 2009 12:44 pm    Post subject: Reply with quote
Full frame cam: 2.0/35 or 1.4/50.
APS-cam: 1.8/24 or 2.0/35

(If possible a 1.4/35 instead of the 2.0/35, but these 1.4-lenses are really expensive.)


PostPosted: Wed Oct 14, 2009 12:58 pm    Post subject: Reply with quote
LucisPictor wrote:
Full frame cam: 2.0/35 or 1.4/50.
APS-cam: 1.8/24 or 2.0/35

(If possible a 1.4/35 instead of the 2.0/35, but these 1.4-lenses are really expensive.)


Samyang new 1.4/35 will be priced low
(we'll have to see about the quality of course)


PostPosted: Wed Oct 14, 2009 1:50 pm    Post subject: Reply with quote
kansalliskala wrote:
Here is a cool gadget:
http://www.dofmaster.com/dofjs.html


The "circle of confusion" is confusing me ..
DOF is relative to picture size Confused


PostPosted: Wed Oct 14, 2009 2:17 pm    Post subject: Reply with quote
kansalliskala wrote:
kansalliskala wrote:
Here is a cool gadget:
http://www.dofmaster.com/dofjs.html


The "circle of confusion" is confusing me ..
DOF is relative to picture size Confused


Ok, set focal lenght to 35mm
scale = meters
aperture = f/1.4
distance = 5 meters

you will see that at wide open with a 35mm lens at a typical shooting distance of 5 meters, you will have more than one meter of depth of field around your subject. This means plenty of safety for a decent sharpness even in a snapshot situation.

If you use the same parameters, but with a 50mm lens, you will see that you will have only half meter of DOF around your subject. This means much more danger of a non sharp picture for the subject.

Therefore, this proves that it is not the same thing to use a 1.4/50 and a 1.4/35 lens. In the typical indoor shooting situation, the 1.4/35 gives you more than double the DOF wide open than a 50mm lens.

Conclusion: invest some money in a 35mm f/1.4 lens.

-


PostPosted: Wed Oct 14, 2009 5:03 pm    Post subject: Reply with quote
For me would be a fast 35mm too. Inside you'll get a frame (assuming you're shooting on 24x36) that's, IMO, not too wide and not too tight (which I find a bit claustrophobic). I chose my 35 f2 for that reason, plus it's reasonably light and balances well with the body which let me to go down at 1/15 or even 1/8 (with a bit of luck).
Cheers, Marty.


PostPosted: Wed Oct 14, 2009 7:29 pm    Post subject: Reply with quote
Orio wrote:
kansalliskala wrote:
kansalliskala wrote:
Here is a cool gadget:
http://www.dofmaster.com/dofjs.html


The "circle of confusion" is confusing me ..
DOF is relative to picture size Confused


Ok, set focal lenght to 35mm
scale = meters
aperture = f/1.4
distance = 5 meters

you will see that at wide open with a 35mm lens at a typical shooting distance of 5 meters, you will have more than one meter of depth of field around your subject. This means plenty of safety for a decent sharpness even in a snapshot situation.

If you use the same parameters, but with a 50mm lens, you will see that you will have only half meter of DOF around your subject. This means much more danger of a non sharp picture for the subject.

Therefore, this proves that it is not the same thing to use a 1.4/50 and a 1.4/35 lens. In the typical indoor shooting situation, the 1.4/35 gives you more than double the DOF wide open than a 50mm lens.

Conclusion: invest some money in a 35mm f/1.4 lens.

-


I was confused with the thing that bigger film gives more DOF - according to the calculator. But then the circle of confusion is bigger for larger film. So DOF is a theoretical concept that is linked to the size of the picture -- and the calculator (and the matemathical model behind it) already makes this interpretation for you and doesn't talk about the picture as such?
Shocked Confused Question


PostPosted: Wed Oct 14, 2009 7:47 pm    Post subject: Reply with quote
I don't know the scientific explanations.
For sure the larger the image base (film, sensor) the thinner the DOF at the same focal lenght.
But for your purpose, it matters more what DOF you can achieve at wide apertures in 135 format and for that a moderately wide fast lens is more useful than a standard fast lens in low light situations.


PostPosted: Wed Oct 14, 2009 9:37 pm    Post subject: Reply with quote
IS or monopod can help a lot also new Canon camera has great high ISO.

I used my 135mm f1.8 Spiratone at wide open pretty successfully. Biotar 75mm f1.5 Pancolar 80 etc also great wide open.


PostPosted: Thu Oct 15, 2009 6:34 am    Post subject: Reply with quote
Orio wrote:
I don't know the scientific explanations.
For sure the larger the image base (film, sensor) the thinner the DOF at the same focal lenght.
But for your purpose, it matters more what DOF you can achieve at wide apertures in 135 format and for that a moderately wide fast lens is more useful than a standard fast lens in low light situations.


I agree with you in the question of lens selection.

But the calculator gives unexpected results:




EDIT:
I'm ashamed to admit but knowledge on physics is not enough to understand wikipedia. And I've studied in a Technical University some time. Embarassed

Here is the theory anyways:
http://en.wikipedia.org/wiki/Depth_of_field


PostPosted: Thu Oct 15, 2009 1:05 pm    Post subject: Reply with quote
If you take a pic with a 35 mm lens at F/1,4 with the subject at 2 m, you wil have in focus 0,27 m. If use a 50 F/1,4 mm lens, you need to take the pic at 3 m to have similar 0,27 m in focus and perspective.

But if you can't go to 3 m., using the 50 mm lens, you have to close the aperture to F/2,8 to obtain similar 0,27 m in focus.

All of that is right if you use a film 35 mm.


PostPosted: Thu Oct 15, 2009 1:27 pm    Post subject: Reply with quote
kansalliskala wrote:
[
But the calculator gives unexpected results:


because the calculator is build on a wrong assumption.
It considers APS-C cameras are making the focal lenght longer. This is the error.
for this reason, with the calculator the same parameters give a narrower DOF compared to FF camera.
But the assumption is wrong, because APS-C cameras do not make the focal lenght longer, they only crop the same image circle that is recorded by the FF camera.
So in reality, what happens with APS-C cameras is that the frame is smaller, but the DOF is exactly the same as you would have with the same lens aperture and distance on a FF camera.

Conclusion: don't mind the APS-C values of that calculator, they are wrong.
Only consider the full frame camera values.

Orio


PostPosted: Fri Oct 16, 2009 1:41 pm    Post subject: Reply with quote
kansalliskala wrote:

But the calculator gives unexpected results:

Yes it's tricky !
Orio wrote:

because the calculator is build on a wrong assumption.
It considers APS-C cameras are making the focal lenght longer. This is the error.

Maybe not.

Note that the calculator allows entries for the size of "circle of confusion" (COC) instead of camera brand/model. So if we set focal length =50 mm, aperture = f/8 & subject distance = 3 m, then we get the the following values for the depth of field, for different cameras

Nikon D3 (FF) DOF = 1.85 m
Nikon D300 (SPS-C) DOF = 1.17
Olympus E420 (4/3) DOF = 0.87

and for different COCs

COC = 0.015 mm DOF = 0.87 m
0.018 1.05
0.020 1.17
0.029 1.78
0.030 1.85

So the calculator is assigning different COC sizes to different sensor/film sizes. The origin of these numbers is given here.. .

http://en.wikipedia.org/wiki/Circle_of_confusion

The COC determines the hyperfocal distance, which determines the DOF, as described here...

http://en.wikipedia.org/wiki/Depth_of_field

Edited to fix 2nd link - Sat 17 October

Last edited by sichko on Sat Oct 17, 2009 8:24 am; edited 1 time in total


PostPosted: Fri Oct 16, 2009 2:12 pm    Post subject: Reply with quote
sichko wrote:
kansalliskala wrote:

But the calculator gives unexpected results:

Yes it's tricky !
Orio wrote:

because the calculator is build on a wrong assumption.
It considers APS-C cameras are making the focal lenght longer. This is the error.

Maybe not.


I think what Orio meant was that you can not compare 35mm lens on a FF (a wide lens) to 35mm on APS-C (a normal lens) and expect to have thinner DOF on the FF - the opposite is what will happen.

If one wants a sensible comparison, one needs to compare cameras with lenses that give the same angle of view. So in this example one would need to replace the 35mm lens on FF camera with a 56mm lens and then the calculator gives 0.48m DOF compared to the 0.79m of the APS-C normal lens. Or if one insists on wide angle, then on APS-C one needs to pick approximately 21.875mm lens (I'm using Canon crop factor) and compare it to the 35mm FF lens - now FF has DOF of 1.29m and APS-C has about 2.25m.

If the focal lenght is the same for different sized sensors, the smaller sensor will provide less DOF as the image needs to be magnified more.

I just ran out of coffee, darn...Sad


PostPosted: Fri Oct 16, 2009 6:04 pm    Post subject: Reply with quote
Anu wrote:

If the focal length is the same for different sized sensors, the smaller sensor will provide less DOF as the image needs to be magnified more.

Yes. And this is recognised by the calculator and indeed by other calculators which allow only COC entries and not camera brand/model or format sizes. See for example....

http://www.tawbaware.com/maxlyons/calc.htm

An interesting point raised in this thread is the effect of working distance.

Orio wrote:
Ok, set focal lenght to 35mm
scale = meters
aperture = f/1.4
distance = 5 meters

you will see that at wide open with a 35mm lens at a typical shooting distance of 5 meters, you will have more than one meter of depth of field around your subject. This means plenty of safety for a decent sharpness even in a snapshot situation.

If you use the same parameters, but with a 50mm lens, you will see that you will have only half meter of DOF around your subject. This means much more danger of a non sharp picture for the subject.

Therefore, this proves that it is not the same thing to use a 1.4/50 and a 1.4/35 lens. In the typical indoor shooting situation, the 1.4/35 gives you more than double the DOF wide open than a 50mm lens.


So at the same working distance a 35 mm lens gives you greater DOF than a 50 mm lens. However in order to fill the frame, you have to work closer with the 35 mm...

estudleon wrote:
If you take a pic with a 35 mm lens at F/1,4 with the subject at 2 m, you wil have in focus 0,27 m. If use a 50 F/1,4 mm lens, you need to take the pic at 3 m to have similar 0,27 m in focus and perspective.

But if you can't go to 3 m., using the 50 mm lens, you have to close the aperture to F/2,8 to obtain similar 0,27 m in focus.

All of that is right if you use a film 35mm.


...when the two DOF values become identical.


PostPosted: Fri Oct 16, 2009 6:27 pm    Post subject: Reply with quote
sichko wrote:
Anu wrote:

If the focal length is the same for different sized sensors, the smaller sensor will provide less DOF as the image needs to be magnified more.

Yes. And this is recognised by the calculator and indeed by other calculators which allow only COC entries and not camera brand/model or format sizes. See for example....

http://www.tawbaware.com/maxlyons/calc.htm


As calculators are part of the thread, I'll share this link to my favorite one: http://eosdoc.com/jlcalc/


PostPosted: Fri Oct 16, 2009 9:03 pm    Post subject: Reply with quote
sichko wrote:
Anu wrote:

If the focal length is the same for different sized sensors, the smaller sensor will provide less DOF as the image needs to be magnified more.

Yes. And this is recognised by the calculator


I am not convinced.


PostPosted: Sat Oct 17, 2009 12:34 am    Post subject: Reply with quote
Orio wrote:
sichko wrote:
Anu wrote:

If the focal length is the same for different sized sensors, the smaller sensor will provide less DOF as the image needs to be magnified more.

Yes. And this is recognised by the calculator


I am not convinced.


OK. Lets consider 3 situations.

1. FF and APS cameras, same lens. Compare the APS picture with that cropped from the centre of the FF. DOF is identical. If you use the calculator you cannot enter CANON 5D (or whatever) for the cropped picture. When you enter a brand/model all the calculator does is assign a value for the circle of confusion (COC) and this depends on the sensor size.

2. Different cameras, different lenses.

D3 (FF) 60mm lens f/2.8 distance = 3 m DOF = 0.42 m
D300 (APSC) 40 mm lens f/2.8 distance = 3 m DOF = 0.63 m

The focal lengths of the two lenses have been chosen to give the same FOV. Here

DOF(APS) > DOF(FF) In fact the ratio is equal to 1.5 - the crop factor and also the ratio of the two COC values.

3. Different cameras same lens

60 mm lens, f/2.8 distance = 3 m for both cameras
D3 DOF = 0.42 m
D300 DOF = 0.28 m

DOF(FF)>DOF(APS) Again a nice ratio of 1.5 ! Accident ?

Of course we have two very different fields of view here - two different pictures. You might argue that it's silly to even calculate the two DOF values. But if you want to you can.

Orio wrote:
because the calculator is build on a wrong assumption.
It considers APS-C cameras are making the focal lenght longer. This is the error.
for this reason, with the calculator the same parameters give a narrower DOF compared to FF camera.
But the assumption is wrong, because APS-C cameras do not make the focal lenght longer, they only crop the same image circle that is recorded by the FF camera.
So in reality, what happens with APS-C cameras is that the frame is smaller, but the DOF is exactly the same as you would have with the same lens aperture and distance on a FF camera.

Conclusion: don't mind the APS-C values of that calculator, they are wrong.
Only consider the full frame camera values.


I think there is some confusion here. I think the calculator is OK.

BTW. The original question was about which lens to use indoors. Of course I would prefer the wider lens as you suggest. But if you have a little more space a longer lens can give you the same DOF

D300 60 mm lens at f/2.8 distance 3m DOF = 0.28 m
D300 40 mm lens at f/2.8 distance 2m DOF = 0.28 m
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