Does a telephoto lens let in less light than a shorter lens at same aperture?
Oct 15, 2017 12:32:26 #
genocolo
Loc: Vail and Gasparilla Island
I am experimenting with a new sigma 100-400 lens on a canon 80d. Trying to capture hummingbird in fairly bright light in The Sonoran Desert. I have noticed that unless I keep shutter speed fairly low the ISO goes sky high when I am at 400mm. Would I be better off using shorter lens and cropping?
Oct 15, 2017 12:39:20 #
The lens itself modify the amount of light due to the magnification, among other things. The question is moot if only for that reason.
Aperture works the same (Controls the amount of light) with one caveat: the depth of field (DoF) will be shorter.
Aperture works the same (Controls the amount of light) with one caveat: the depth of field (DoF) will be shorter.
Oct 15, 2017 12:39:29 #
It shouldn't.
Does the aperture on your lens remain the same at 100 and 400?
If the lens is labeled something like F/4.0 -F/6.3 the aperture value is smaller at 400.
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Does the aperture on your lens remain the same at 100 and 400?
If the lens is labeled something like F/4.0 -F/6.3 the aperture value is smaller at 400.
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Oct 15, 2017 12:40:44 #
genocolo wrote:
I am experimenting with a new sigma 100-400 lens on a canon 80d. Trying to capture hummingbird in fairly bright light in The Sonoran Desert. I have noticed that unless I keep shutter speed fairly low the ISO goes sky high when I am at 400mm. Would I be better off using shorter lens and cropping?
No, the amount of light let in is the same.
What's probably happening is that your lens changes aperture based on how you zoom it. Some lenses are built to change the aperture as you zoom. if your lens is marked "f/5-6.3" or something instead of "f/5" then that's what's happening.
At the shortest the lens can go it's an f/5 lens, but at some point when you zoom, it goes to f/5.6 (or whatever the other f/stop is.)
During the day in bright light your exposure should be something like:
f/16
Shutter speed = 1/250
ISO = 200
It might vary some but if it's bright and daylight, that's it. There is no reason for your ISO to skyrocket unless you are using some very high shutter speed.
What are your settings?
Oct 15, 2017 12:44:10 #
You need to first get control of your camera by turning OFF auto ISO and picking a single ISO you can live with. Second, is your lens fixed aperture or variable? If variable, it is likely closing down to a smaller aperture as you zoom out (which is why your auto ISO is going up.). Try putting the camera on manual or shutter priority with a fast shutter speed and use the highest ISO that delivers the quality you need. Run some tests to see if that combo works for you.
Oct 15, 2017 12:46:58 #
As previously pointed out, if your lens has an aperture that varies with its magnification that would be one cause. A remote possibility is that the lens design alters the LT, light transference, with high magnification.
To answer the question asked in your thread title. Yes.
Better lenses have better LT numbers which is discussed almost never.
To answer the question asked in your thread title. Yes.
Better lenses have better LT numbers which is discussed almost never.
Oct 15, 2017 12:55:58 #
The answer to your question is NO. My guess is your lens is variable aperture which gets lower (higher number) as you zoom more. That's why fast telephoto lenses are so large. Best of luck.
Oct 15, 2017 13:02:37 #
Rich1939 wrote:
As previously pointed out, if your lens has an aperture that varies with its magnification that would be one cause. A remote possibility is that the lens design alters the LT, light transference, with high magnification.
To answer the question asked in your thread title. Yes.
Better lenses have better LT numbers which is discussed almost never.
To answer the question asked in your thread title. Yes.
Better lenses have better LT numbers which is discussed almost never.
How is that even possible? The LT number is a function of the number of elements in the lens.
Oct 15, 2017 13:04:17 #
genocolo your Sigma 100-400mm f/5-6.3 DG OS HSM Contemporary Lens for Canon EF is a variable aperture lens... The longer you set the focal length the less light is available to your sensor... There are compelling reasons why commercial shooters typically use "Prime" lenses, (or fixed aperture zoom optics) this is one of the major ones...
Best Advice? Use off camera speed-lights... this is the most expedient scenario that I've discovered for photographing hummers...
btw: Canon's 600EX RT is soooo much better than Nikon's late entry into radio receiver empowered speedlites.
That said I've been able to capture hummingbirds in ambient at f/6.3 with Nikon's amazing new AF-P 70-300mm f/4.5-6.3G ED VR (Pulse Focusing Motor)... This awesome DX Nikkor is "Feather Light" unlike the Sigma which at 1160g is rather heavy and sadly lacks a tripod foot (like what was Sigma thinking? Seriously!)
Example below:
Camera: Nikon D7200
Lens: AF-P Nikkor 70-300mm f/4.5-6.3G ED VR
Focal Length: 300mm; Aperture: F6.3; Shutter Speed: 1/1000 second (effective focal length 450mm)...
Venue: Lake Fairfax Park, Reston VA
Hope this helps or is at least food for thought...
I wish you well on your journey genocolo
Best Advice? Use off camera speed-lights... this is the most expedient scenario that I've discovered for photographing hummers...
btw: Canon's 600EX RT is soooo much better than Nikon's late entry into radio receiver empowered speedlites.
That said I've been able to capture hummingbirds in ambient at f/6.3 with Nikon's amazing new AF-P 70-300mm f/4.5-6.3G ED VR (Pulse Focusing Motor)... This awesome DX Nikkor is "Feather Light" unlike the Sigma which at 1160g is rather heavy and sadly lacks a tripod foot (like what was Sigma thinking? Seriously!)
Example below:
Camera: Nikon D7200
Lens: AF-P Nikkor 70-300mm f/4.5-6.3G ED VR
Focal Length: 300mm; Aperture: F6.3; Shutter Speed: 1/1000 second (effective focal length 450mm)...
Venue: Lake Fairfax Park, Reston VA
Hope this helps or is at least food for thought...
I wish you well on your journey genocolo
Oct 15, 2017 13:05:24 #
Pegasus wrote:
How is that even possible? The LT number is a function of the number of elements in the lens.
You just answered your own question.
f/8 on a lens with less elements will transfer more light than f/8 on a lens with more elements
Oct 15, 2017 13:07:46 #
genocolo
Loc: Vail and Gasparilla Island
It is variable, from f5-6.3. At about 230 on up, it is 6.3.
Am I correct in assuming that a lens with say a 90mm filter size will let in more light at the same aperture that say 67?
How high an iso do u think the 80d can effectively handle?
Am I correct in assuming that a lens with say a 90mm filter size will let in more light at the same aperture that say 67?
How high an iso do u think the 80d can effectively handle?
Oct 15, 2017 13:23:24 #
Sorry, but I'm not going to let you get away with that one.
Your first statement was:
Rich1939 wrote:
As previously pointed out, if your lens has an aperture that varies with its magnification that would be one cause. A remote possibility is that the lens design alters the LT, light transference, with high magnification.
To answer the question asked in your thread title. Yes.
Better lenses have better LT numbers which is discussed almost never.
To which I replied about your "remote possibility":
How is that even possible? The LT number is a function of the number of elements in the lens.
And then you post this tripe:
You purposefully conflated the use of different lenses to mask your unbelievable statement about lenses altering the LT, magically.
The answer to the OP's question is very simple. There is a finite amount of light allowed in by the objective lens. As you increase the magnification of the zoom, you cut out a lot of light and the image gets darker. This is well known to shooters, birders and other people who use zoom optics.
We don't see that very much in camera lenses because the zoom factor is so low. We're talking a difference in magnification between 2X and 4X or some such, but it's there.
That's the reason zoom lenses with magnification have bigger objectives. More light is needed to get anything at the higher mags.
Your first statement was:
Rich1939 wrote:
As previously pointed out, if your lens has an aperture that varies with its magnification that would be one cause. A remote possibility is that the lens design alters the LT, light transference, with high magnification.
To answer the question asked in your thread title. Yes.
Better lenses have better LT numbers which is discussed almost never.
To which I replied about your "remote possibility":
How is that even possible? The LT number is a function of the number of elements in the lens.
And then you post this tripe:
Rich1939 wrote:
You just answered your own question.
f/8 on a lens with less elements will transfer more light than f/8 on a lens with more elements
f/8 on a lens with less elements will transfer more light than f/8 on a lens with more elements
You purposefully conflated the use of different lenses to mask your unbelievable statement about lenses altering the LT, magically.
The answer to the OP's question is very simple. There is a finite amount of light allowed in by the objective lens. As you increase the magnification of the zoom, you cut out a lot of light and the image gets darker. This is well known to shooters, birders and other people who use zoom optics.
We don't see that very much in camera lenses because the zoom factor is so low. We're talking a difference in magnification between 2X and 4X or some such, but it's there.
That's the reason zoom lenses with magnification have bigger objectives. More light is needed to get anything at the higher mags.
Oct 15, 2017 13:31:19 #
genocolo wrote:
It is variable, from f5-6.3. At about 230 on up, it is 6.3.
Am I correct in assuming that a lens with say a 90mm filter size will let in more light at the same aperture that say 67?
How high an iso do u think the 80d can effectively handle?
Am I correct in assuming that a lens with say a 90mm filter size will let in more light at the same aperture that say 67?
How high an iso do u think the 80d can effectively handle?
Go outside, set the camera on P. Take pictures of the same subject doubling the ISO with each shot. Look at the images on the computer and find the one where the noise level is objectionable to you. Now lower your ISO.
Noise in an image is more of a problem to some than others.
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Oct 15, 2017 13:33:00 #
genocolo wrote:
I am experimenting with a new sigma 100-400 lens on a canon 80d. Trying to capture hummingbird in fairly bright light in The Sonoran Desert. I have noticed that unless I keep shutter speed fairly low the ISO goes sky high when I am at 400mm. Would I be better off using shorter lens and cropping?
Is your shutter speed higher when using the shorter lens?
To answer the last question. No you're not better off using shorter lens then crop.
Oct 15, 2017 13:37:02 #
Pegasus wrote:
Sorry, but I'm not going to let you get away with ... (show quote)
I didn't purposely conflate a thing, I attempted to answer the original question "Does a telephoto lens let in less light than a shorter lens at same aperture?" Or do you purposely ignore that because it wasn't repeated in the body of the thread? My answer should have been a qualified yes as two lenses at the same aperture can and often do require different exposure settings not just between telephoto and smaller focal lengths.
As far as a remote possibility well it is just that isn't it?
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