petrochemist Loc: UK

Both are completely different to the situation with crop sensors. Take your pizza analogy & give everyone in the large room a slice of pizza, but then only count those in the middle of the room & ignore anyone near the edges. This is exactly what happens if you mount a FF lens on a crop body, light density, from an evenly lit scene, does not change - so exposure doesn't change.

Total light only has any relevance for very dim scenes when considering the noise. It's a complete red herring in normal photography.

Your zoom torch is changing the optics, so more appropriate for considering a lens adapted via a focal reducer. Here we have additional elements in the adapter that bend the light so as to give nearer to the un-cropped FOV. Concentrating the light into a smaller area makes the light density higher - so the crop sensor sees a brighter image (with my focal reducer 1 stop brighter). This seemingly magical device still uses the proper definition of f-stops - the physical aperture/entrance pupil remains the same size, but the extra optics have reduced the focal length. Teleconverters do the same thing in reverse, spreading the image to give a longer focal length but at reduced brightness.

petrochemist Loc: UK

The difference between f-stops & t-stops is purely down to absorbance & reflection of light by the glass of the lens. Neither has any bearing on sensor format. For videographers t-stops become very important if zooming or changing lenses during a scene - they need the resultant image to be of exactly the same brightness. They have no relevance for still photography where DOF is more important than precise consistency of exposure.

In normal usage there is only small changes in the two values, but if shooting UV images - where lenses tend to absorb most of the 'light' - there will usually be very significant differences. By 350nm most lenses see transmission drop by more than 10 stops compared to their visual performance. Fortunately TTL metering solves this issue for the few of us who are interested in recording images in UV.
FWIW there can be significant changes for Infra red imaging as well, most lenses transmit NIR in a similar way to visual light, but some of my Panasonic lenses show a significant drop in transmission when moving into the infra red. I strongly suspect this is a factor of the anti reflection coatings, which are clearly optimised for visual use.

baron_silverton Loc: Los Angeles, CA

The short answer is: NO. Aperture provides equivalent exposure regardless of sensor as long as you are also at the same shutter speed and same ISO.

The explanation is as follows:

To answer your question - exposure is not effected by sensor size. Some people have suggested that noise is more on an apsc at the same aperture and although this is often true, it is not necessarily true - IQ and noise are a totally different discussion than exposure.

The noise difference often has to do with pixel density and this can vary widely depending on the age of the sensor etc. Generally, more pixels gives better resolution, but worse noise performance due to heat - the more packed in the pixels are the more the heat from each effects the other. Generally, apsc sensors have a tighter pixel pitch because more pixels are jammed into a smaller area. As sensor technology advances they are getting better and better at minimizing this and that is why newer high resolution sensors have much better noise performance than they used to.

What does change (or seem to change) when using a crop sensor camera at an equivalent aperture to full frame (FF) is the apparent depth of field (DOF). For a given framing of a subject (angle of view in the view finder) you have to multiply by the crop factor to get the equivalent DOF on a FF.

The reason for this has NOTHING to do with the lens!

It is purely because of the distance to subject. A crop sensor camera with a 1.5 crop factor means that if, for example, you are shooting a head and shoulders shot of your subject with a 50mm lens, in order to achieve this framing in the camera you would have to step back to a distance roughly equivalent to the distance that you would have to be with a FF camera and a 75mm lens (50 X 1.5 = 75).

This is the reason people say a 50mm lens is a 75mm lens on a crop sensor. It is NOT. It is, and will always be, a 50mm lens - nothing magically changes its focal length - but because the camera has cropped you in by a 1.5 crop factor (just like cropping in post - except its automatic because the sensor is smaller) you now have a field of view that is equivalent to a longer lens - 75mm in this case when using a 50mm.

The result of this of course is that your distance to subject for the same shot is 1.5 times farther away, and as such your DOF is less shallow - remember DOF gets more and more shallow as you get closer to your subject and deeper and deeper the farther away you are as you approach infinity for the focal distance of the lens.

So, if you are shooting at F/4 for example but you are on a crop sensor camera you would multiple 4 by 1.5 (or whatever the crop factor is 1.6 for canon) and get an f/6 DOF equivalent. UNDERSTAND THAT YOU ARE NOT SHOOTING AT F/6. If you used your FF camera and simply backed up to the spot you were standing to get the shot on your crop sensor camera the DOF at f/4 wold be exactly the same.

So, for exposure as far as what your light meter will tell you there is NO DIFFERENCE at all between the same aperture whether you are using a crop sensor of a FF. There may be noise differences but this has nothing to do with the lens- this is a sensor issue. And finally, your DOF at any given photo framing will be 1.5 times deeper than the equivalent photo framing on a FF, but this is only because you will be standing 1.5 times farther from the subject - DOF HAS NOT ACTUALLY CHANGED AT ALL - IT IS THE SAME LENS AND APERTURE. What has changed is just your distance to subject.

On your 90mm 2.8 macro Tamron - your field of view at any given distance will be equivalent to the field of view of a 135mm lens - this is actually a good thing for macro - farther distance from subject can be helpful. Also, for Macro photography you need to stop way down as DOF is very shallow at macro distances even with small apertures so the DOF issue with distance should not be a relevant factor to your Macro photography. For portraiture it can be an issue which is why most people prefer FF for portraits.

I hope this helps.
-B

petrochemist Loc: UK

DoF usually refers to depth of field in the final image. This is a subtly different parameter to depth of focus on the sensor. Images from a small sensor have to be enlarged more to create a standard sized print, which changes how blurred something can be before the observer can see the blur. Depth of focus remains the same, depth of field does not as this relies on parts of the process that have to be changed.

Interesting you mention everything being up-side down, because that is always* the case with images through a lens. Antone who's looked at the ground glass of a large format camera can confirm this.

*The only exceptions are where a virtual image is formed in the system & then viewed by more optics - as in microscopes, telescopes & & viewfinders.

petrochemist Loc: UK

The obvious way to compare is to use the same camera. Take a static evenly lit scene, shoot in FF mode, then switch to crop mode & shoot again. Keep all other parameters the same. The exposure does not suddenly need adjusting when you switch to crop mode. FOV will change, but not the brightness of the image.
Alternatively you can take a single shot, print it twice (same settings) and then cut the outer pert off one of the prints. This is exactly what a crop sensor is doing to the lenses image circle.

For over a century millions of photographers used multiple film formats (often with external meters) & never had to adjust exposure between formats.
Digital has been around a much shorter time but I'm sure there are also millions of us who use multiple digital formats as well, fewer use external meters but there is still no need to cater for format size.

epd1947

It's really pretty simple - the amount of light emerging out of the back of a lens is exactly the same regardless of the camera that lens is mounted on. The field of view captured will vary with the size of the sensor, but the exposure level of whatever field of view is captured will be exactly the same. Depth of field varies because, with a smaller sensor camera, you either need to move further back from the subject (assuming you are keeping the same focal length lens) or select a shorter focal length lens (if you want to capture the same field of view as you would with a camera with a larger sensor without changing your distance to the subject) - either of those actions broadens the depth of field.

User ID

You mean IF, not IS.

Usually not much, but for a reeeeelly severe example, try the current version of the Nikon 28-300.

CamB Loc: Juneau, Alaska

You lost me at step 2. Suddenly I was back in Algebra or French class in high school hoping the they wouldn't call on me. Fortunately my teachers quickly realized calling on me for answers in these subjects was just a waste of time for everyone.
...Cam

imagemeister Loc: mid east Florida

Yes IF .....IF .....IF - thanks

wdross Loc: Castle Rock, Colorado

I have viewed Tony's video more than twice. There are UHHers that have indicated aperture "changes" with format and cite Tony's video as "evidence". And if I was an ignorant newbie, I would be inclined never to purchase 4/3rds and possibly not even an APS-C because of the implied "aperture change" between formats. He never directly states he is only talking depth of field. Obviously, narrow depth of field and high ISO are very important and high on his list of "needs" of a system. And full frame fits that niche very well. But narrow depth of field and high ISO are not a major consideration for a lot of us. For me, the larger depth of field for the same f-stop is a bonus, not a liability. And the new softwares are quite effective at fixing any noise at ISO 6400 and above. Tony has indicated carrying 9 pounds of full frame is not much more difficult than carrying the same angle of view in 4/3rds at 4 pounds. Really? 9 pounds is not much different than carrying 4 pounds? How many times has the subject, "How can I lighten the load?", come up on UHH? (Which I agree does not always require a change of format although it is always an option.)

Tony should be up front with the statement "the effective depth of field" when looking at different formats, not "the effective aperture". That indicates the light capturing abilities of a lens changes with format even when the aperture does not change nor its abilities to capture light at that aperture.

larryepage Loc: North Texas area

Like many who write for a living, especially today, Tony Northrup is an "opinion as fact" person. He is also a "snapshooter," with what appears to be pretty limited artistic vision. Those who fixate on what he says seem to tend toward becoming the same sort of phototechnologist that he is. That would be less of a problem if he demonstrated a deeper knowledge of the things he likes to write about.

The truth is that given the state of photographic technology today, while some of this is interesting to talk about (for a while), most of it combined has less than a 5% impact on the actual impact of most photography displayed on this site. Fixing all of the technical problems in most photographs here still will not fix the lack of interest and viewability that some additional care with subject selection, composition, and presentation (post processing) choices will fix. Let's face it...the worst of what is available from the major makers is really still pretty serviceable.

The same attitude comes up every time there is a post asking how to design, say, exposure triangle drudgery for a son or daughter who wants to learn photography. Forget that. It will come. Talk about seeing, and capturing what you see. That's what viewers care about. Not f/stops and depth of field that have been discussed to the depth of the field.

Silverrails

Nikon Crop-Factor of 1.5 x the Aperture ( ex.50mm ) would be present an actual F.O.V. (Field of View) of 75mm. This would not apply on a Full Frame Camera. If I am misunderstanding this please enlighten me. Thank you.

xt2 Loc: British Columbia, Canada

xt2 Loc: British Columbia, Canada

selmslie Loc: Fernandina Beach, FL, USA

An older macro lens does indeed change the effective aperture as you focus closer (or add extension tubes) because the aperture moves further from the sensor or film plane. My 105mm Lester Dine macro behaves this way as did the 55m Micro Nikkor. I'm not sure about the 60mm Micro Nikkor that I no longer own.

But a newer macro lens, even if it's not designated as IF (internal focus) can behave differently.

My 60mm AF 2.8D Micro Nikkor will maintain the specified aperture from infinity to 1:1 between f/5 and f/32, the normal range I would use for macro photography,.

But from f/2.8 to f/5 the effective aperture adjusts as the focus distance changes. In other words, I can set it to f/2.8 when focused at infinity but the aperture changes as I focus closer until at 1:1 it shows f/5.