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Is This In Fact True?
Sep 26, 2016 13:13:54 #
On doing some research a photo blogger stated that although a given lens for example is stated as f/2.8, if it's meant for a medium format the physical size of the lens when focused down to 35 or apsc formats is actually faster since the large elements are actually allowing more light into the sensor. What gives? He actually showed two examples whereby he took the exact picture with the same camera settings. The images were actually a bit brighter with the medium format 2.8 vs the 1.4 nikkor meant for 35mm.
Assuming this to be true wouldn't it be a good thing to purchase used medium format lenses for an E mount camera and thus would get the advantage of a very fast lens at a cheap price?
Assuming this to be true wouldn't it be a good thing to purchase used medium format lenses for an E mount camera and thus would get the advantage of a very fast lens at a cheap price?
Sep 26, 2016 13:19:29 #
I think the f number is a ratio of aperture size to focal length. ie: if the lens is a 50mm and the aperture is 25mm, the f number would be 50/25= 2 or f2.0
Sep 26, 2016 13:21:35 #
So then a larger front element such as an 80 2.8 zeiss hasselblad should actually be faster on a "35mm" size sensor?
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Sep 26, 2016 13:23:11 #
The f-stop is a ratio of the diameter of the entrance pupil to its focal length. It's that simple. Projecting an image on an FX sensor or a DX sensor doesn't change either the focal length or the diameter of the entrance pupil. Thus, no change in brightness.
--Bob
--Bob
busmaster2 wrote:
On doing some research a photo blogger stated that... (show quote)
Sep 26, 2016 13:24:07 #
No.
--Bob
--Bob
busmaster2 wrote:
So then a larger front element such as an 80 2.8 zeiss hasselblad should actually be faster on a "35mm" size sensor?
Sep 26, 2016 13:24:28 #
Your "photo blogger" is delusional ! The "brightness" of f2.8 on one lens is the same on every other lens marked as f2.8 ! Please give a link !
Sep 26, 2016 13:25:23 #
rmalarz wrote:
The f-stop is a ratio of the diameter of the entrance pupil to its focal length. It's that simple. Projecting an image on an FX sensor or a DX sensor doesn't change either the focal length or the diameter of the entrance pupil. Thus, no change in brightness.
--Bob
--Bob
So then what would account for the brighter image in the examples I mentioned? The same shutter speeds and ISO were used. The only difference being that the medium format lens was set at 2.8 and the nikkor was 1.4.
Sep 26, 2016 13:26:28 #
busmaster2 wrote:
On doing some research a photo blogger stated that... (show quote)
I don't think so and N-E-Way you might find that MF Lenses are more expensive than those for 35mm type cameras.
Sep 26, 2016 13:27:23 #
Sep 26, 2016 13:29:11 #
A lens designed for a format larger than the sensor (or film format) casts a larger than necessary image circle. The extra light it lets in falls off to the sides. If the resulting image looks brighter, it's receiving extra light reflected from the walls of the camera body, not directly from the lens. The image looks brighter but of lower contrast. Betcha a donut. :)
Sep 26, 2016 13:30:12 #
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Sep 26, 2016 13:32:32 #
You might be right...but in fact they do take wonderful images. I have a bunch of old zeiss biometars and russian mediums that are amazing sharp and contrasty on my a7II and R. Plus I have the satisfaction of being able to purchase a lot of lenses for relatively little money.
Sep 26, 2016 13:33:36 #
There is a reason hand-held light meters do not have a compensation/adjustment/setting for whatever format you are using.
There is no difference.
Mythbusters say: FALSE.
There is no difference.
Mythbusters say: FALSE.
Sep 26, 2016 13:35:11 #
That was what I had been thinking. I was just curious what you guys thought. Bloggers have been known to BS right?
Sep 26, 2016 13:45:38 #
I regularly use my Zeiss lenses (Hasselblad) on my Nikon D700/D800e. The f-stops are the same and the images look exactly the same whether photographed with a Nikkor lens or the Zeiss lens with both set to the same f-stop.
Now, there may be a bit of an issue introduced by the transmittance of the lens. That is a completely different topic than f-stops. f-stops do not take into account the amount of light that is allowed to pass through the lens. Lens coatings, number of elements/groups within the lens can reduce the amount of light reaching the focal plane.
--Bob
Now, there may be a bit of an issue introduced by the transmittance of the lens. That is a completely different topic than f-stops. f-stops do not take into account the amount of light that is allowed to pass through the lens. Lens coatings, number of elements/groups within the lens can reduce the amount of light reaching the focal plane.
--Bob
busmaster2 wrote:
So then what would account for the brighter image in the examples I mentioned? The same shutter speeds and ISO were used. The only difference being that the medium format lens was set at 2.8 and the nikkor was 1.4.
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