1950Dan Loc: Lockwood, Nevada

Would a f/1.4 98.6mm lens and an f/4 98.6mm lens transmit the same exposure at f/16? Or to ask another way does a big, heavy, high dollar lens give more light throughout the spectrum?

PHRubin Loc: Nashville TN USA

No! F/16 is f/16 no matter how wide open the lens could go. For any given focal length the light transmitted at any f stop is the same for any lens. But at the widest the lens with the widest aperture will work best in low light and have the best bokeh.

RichardTaylor Loc: Sydney, Australia

Q1- yes.
Q2 - It depends on the lens maximum (wide open) aperture, For the same aperture no, however if the big heavy, high dollar, lens has a faster maximum aperture then yes.

jdedmonds

No, only up to f/4, from whence they will transmit the same quantum of light.

Photocraig

With all modern SLR cameras--even the film one's open the mounted lens to MAXIMUM "viewing" aperture for a brighter image in the viewfinder. That's because a view through the lens "Stopped down" to "taking" aperture would be quite dim. The camera, upon shutter actuation "stops down" the lens to the "taking" aperture the photographer has chosen. As RHRubin says the taking f stop (f16) is the same on all the same focal length lenses. What is different, and useful for photographers is that the "Viewing" aperture is larger on the largest maximum aperture lens. This yields a brighter image in the viewfinder so you can compose and frame better better and you can FOCUS (or auto focus) more accurately. A dark frame makes it hard to see those branches growing out of a subject's heads or items intruding into the frame.

C

Of course, a wider maximum aperture adds to the creative possibilities with that lens and facilitated better low light performance as well. The Larger the maximum aperture of the lens is the higher is the price, size and weight of the lens.

Uuglypher Loc: South Dakota (East River)

Given use of the same ISO and shutter speed, both lenses would offer the same exposure if each were set at f/16, or, for that matter, at any aperture setting up to f/4.

The advantage of the f/1.4 lens is that it offers three full stops more exposure ( 3 more doublings of light admitted...that’s eight times more light) than offered by the f/4 lens. (Up to f/4 both lenses offer equivalent exposures.)

Dave

Uuglypher Loc: South Dakota (East River)

sorry...dupe post

TriX Loc: Raleigh, NC

Depends on the lenses. Typically the fstop is a calculated value, not a measured one, and two lenses with the same fstop may transmit different amounts of light. I recently tested and posted on two f2.8 lenses that were about 2/3 stop difference in light transmission at the same aperture. If you really want to compare actual light transmission, then Tstop is the appropriate metric.

BebuLamar

And in this case it's not necessarily the more expensive one would transmit more light.

SharpShooter Loc: NorCal

No, but better quality advantages aside, it will focus faster and more accurately in low light and have a much brighter eyepiece to work with.
SS

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

Only if they have the same light transmission capability. Fstops are ratios of aperture to focal length, and determined by physical dimensional measurement. A Tstop is an actual light transmission measurement. A lens with a Tstop of F16 will always transmit the same amount of light as another lens with the same Tstop. Fstops are less reliable as an indicator of light transmission.

For those who were unaware of light transmission characteristics of lenses and Tstops - that is why there are differences in exposure between lenses set to the same fstop.

https://fstoppers.com/education/why-cinema-lenses-are-measured-t-stops-and-whats-difference-f-stop-158541

Kiwi1 Loc: New Zealand

To reply to the core of your question .. does the big heavy lens high dollar lens give more light throughout the spectrum? Well there is not one correct answer. Yes in theory the lens at f/ 1.4 will give more light wide open than the lens at f/4 wide open, that's the simple part.

The second part is harder to explain but the quality of the glass and the number of glass elements may have an impact on gathering light of better quality that is recorded at the sensor plane. Thing is controlling the light as it passes through the lens is highly complex and often requires the light ray to be bent and that is where better quality glass makes the difference. Things like CA, and lens distortion do effect the ultimate quality of the light reaching the sensor and to some degree would effectively reduce the light value. Some better quality lenses produce higher contrast generally because the lens makes a better job of keeping light from the subject more precise. A lower quality lens is more likely to record somewhat damaged light as the result of passing though poorer quality glass and that almost certainly would result in less light on the sensor at the same f stop.

By way of a simple example when you wash the windows of you house you sometimes notice how much brighter a room is, although not for the exact same reasons the total light entering the room increases because the dirt is removed, still the same amount of light outside but the quality reaching the room is better, the path of the light is more direct and more light rays have entered the room without bending by particles of dirt.
So the higher quality lens is like a 'cleaner window' and always stays 'cleaner' because of the higher quality materials to make the glass and more precise manufacturing process and that's why you pay the extra money.

Tronjo Loc: Canada, BC

The answer is "Probably not". Even at same aperture the two will transmit different amount of light due to different reflection and absorption losses. Often, more expensive and with more elements (surfaces) lens will transmit less then a simpler one.

speters Loc: Grangeville/Idaho

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

The only thing that matters is the amount of light reaching the sensor. If you had a 1.4 lens stopped down to f16 and an f4 lens stopped down to f16 both lenses are giving the sensor an f16 amount of light (no difference). Now, on the other side, if both lenses are wide open then the 1.4 lens is giving you about 3 more stops of light than the f4 lens. And, yes, at this end I would suspect the 1.4 lens would focus a little faster. But you probably would not notice the difference in amount of time it takes to focus between the two lenses. Enjoy and keep on shooting until the end.