jcs

Well, the combination of an 80mm lens and a 0.7x focal reducer does have a focal length of 56mm.  After all, focal reducers really do reduce focal length.  You could prove this to yourself by measuring the separation of photographed stars or I could prove it to you in my lab using the nodal slide on my optical bench.  And if you use that 56mm lens on FF (24x36mm) format, then *it is* a FF 56mm lens.  In this case, the use of a focal reducer together with an 80mm lens is a perfectly valid way of designing and creating a true 56mm lens.  As I mentioned in my earlier post, the only possible reason it will look different from any other 56mm lens will be due to lens/reducer aberrations and other flaws. 

First of all, you didn't even make the test so I could just tell you "No way" right there and then.
But you are in luck, I'm not small minded.
So here is a chance for you at the $100.
Look at the test I made yesterday with the two pictures of the same flowers and identical settings apart from the "equivalent" lens.
Convince me that my eyes are wrong and that one of the pictures isn't darker than the other.

Do that and you have proven to me that the "equivalent" lens thing is at least slightly for real (there are still going to be plenty of things that separates a lens from another imo).
I post new pics every day on my Instagram since getting the adapter and have uploaded a quick video test.
Just sold my A7 five minutes ago so the next video will be after I have bought an A7s.
It might be a while because as some of you may know, I pay very very little for my gear compared to retail and list prices.
Sniffing out a deal sometimes takes a little time and dedication
(plenty of more stills to come though)

Here's a basic formula:
When possible, take away all the light and carefully add light tuned for the story and emotion of the scene. Look at how often everything is dark, or overall not very bright in classic films. Paint with light. There are tons of books on this subject. Shoot at night and wet down the street. Set the frame rate to 24 (or 23.976), shutter 1/48 (or 1/50). That's for normal shots, you can go all over the place for emotional effect of the scene. Protect highlights so they don't clip and pay careful attention to exposure to keep skin tones in the sweet spot for your camera. Study film behavior for highlights and adjust your look in post to match the highlight and color response of film. Film generally never gets super white. Use a diffusion filter of some kind. Blur a little in post if necessary and add full resolution film grain (blur may not be needed if diffusion is used). Make sure there are no digital artifacts such as aliasing or Moire. Use depth of field to help tell the story by helping the viewer focus on what's important in the scene. If your camera has rolling shutter, make sure to move the camera in a way to minimize it. Try to make the scene a little 'unreal', in a way you would not see in normal everyday life. Like in a dream.

You either have a bad memory or you didn't read the thread. The simulation wasn't created for you. Matthias denied what Timotheus wrote...
He is talking about the math behind it.

No you cant. Look at the Tony Northup frame I posted. It clearly proves that you can replicate the image from a large sensor in the way YOU earlier suggested.
I tell you what. Take the three lenses and sensor sizes you listed in your first post. Take three photos from the same distance of the same subject. A person with a background similar to the example I posted.
I will give you $100 it they turns out exactly the same. 
tweak likes this
As you can read Matthias suggest it can't be done the way You Timotheus suggest. In other words the math is being denied. 
That's why the simulation was created as it removes the imperfection of the lenses. Meantime the math is no longer the point of discussion, or so it seems.
Film is not reality. Even more so in this day and age, as there are more and more CG generated movies produced. A reality you will have to live with.
@ Matthias, still waiting for the $100,-. btw I settle for a lens.
...and btw I dig this thread and the adapter results.

Even crappy jpegs look decent pretty much straight from camera.

Here's a basic formula:
When possible, take away all the light and carefully add light tuned for the story and emotion of the scene. Look at how often everything is dark, or overall not very bright in classic films. Paint with light. There are tons of books on this subject. Shoot at night and wet down the street. Set the frame rate to 24 (or 23.976), shutter 1/48 (or 1/50). That's for normal shots, you can go all over the place for emotional effect of the scene. Protect highlights so they don't clip and pay careful attention to exposure to keep skin tones in the sweet spot for your camera. Study film behavior for highlights and adjust your look in post to match the highlight and color response of film. Film generally never gets super white. Use a diffusion filter of some kind. Blur a little in post if necessary and add full resolution film grain (blur may not be needed if diffusion is used). Make sure there are no digital artifacts such as aliasing or Moire. Use depth of field to help tell the story by helping the viewer focus on what's important in the scene. If your camera has rolling shutter, make sure to move the camera in a way to minimize it. Try to make the scene a little 'unreal', in a way you would not see in normal everyday life. Like in a dream.

Here's a basic formula:
When possible, take away all the light and carefully add light tuned for the story and emotion of the scene. Look at how often everything is dark, or overall not very bright in classic films. Paint with light. There are tons of books on this subject. Shoot at night and wet down the street. Set the frame rate to 24 (or 23.976), shutter 1/48 (or 1/50). That's for normal shots, you can go all over the place for emotional effect of the scene. Protect highlights so they don't clip and pay careful attention to exposure to keep skin tones in the sweet spot for your camera. Study film behavior for highlights and adjust your look in post to match the highlight and color response of film. Film generally never gets super white. Use a diffusion filter of some kind. Blur a little in post if necessary and add full resolution film grain (blur may not be needed if diffusion is used). Make sure there are no digital artifacts such as aliasing or Moire. Use depth of field to help tell the story by helping the viewer focus on what's important in the scene. If your camera has rolling shutter, make sure to move the camera in a way to minimize it. Try to make the scene a little 'unreal', in a way you would not see in normal everyday life. Like in a dream.

Here's a basic formula:
When possible, take away all the light and carefully add light tuned for the story and emotion of the scene. Look at how often everything is dark, or overall not very bright in classic films. Paint with light. There are tons of books on this subject. Shoot at night and wet down the street. Set the frame rate to 24 (or 23.976), shutter 1/48 (or 1/50). That's for normal shots, you can go all over the place for emotional effect of the scene. Protect highlights so they don't clip and pay careful attention to exposure to keep skin tones in the sweet spot for your camera. Study film behavior for highlights and adjust your look in post to match the highlight and color response of film. Film generally never gets super white. Use a diffusion filter of some kind. Blur a little in post if necessary and add full resolution film grain (blur may not be needed if diffusion is used). Make sure there are no digital artifacts such as aliasing or Moire. Use depth of field to help tell the story by helping the viewer focus on what's important in the scene. If your camera has rolling shutter, make sure to move the camera in a way to minimize it. Try to make the scene a little 'unreal', in a way you would not see in normal everyday life. Like in a dream.

@tupp the equivalence equations and test images don't claim to be pixel perfect, only a tool to set up cameras and lenses as equivalent as possible. You've looked at them all and proclaimed, "ha HA! The two images aren't perfect so it's invalid!", right? Then when shown pixel perfect computer simulations (which can in fact model any defect/transfer functions you'd like) you proclaimed, "simulations aren't reality so it's invalid!". I was providing information I thought would be helpful. If it doesn't work for you, no worries.
If anyone can show that any specific lens has special properties only available for the format the lens was designed for, I look forward to seeing the results.

'Look' works as it captures any possible effect at all. The argument has been: does sensor size, by itself, create any specific visual effect or look, whatsoever, or not.
Do lenses made for different formats have any special characteristics related to the intended capture format? One could argue size, however some full frame lenses are bigger than some medium format lenses. I had asked Brian Caldwell if he'd be making a medium format Speed Booster and he said no. There are now many very high quality full frame lenses and medium format lenses have no unique properties, so there was no point. A lens is defined by its optical transfer function, that's it.
In this thread we learned that some medium format lenses can be found for very low cost. Combined with a focal reducer for full frame bodies that provides a cost effective way to get shallow depth of field, swirly bokeh, or other desired artistic looks. That's cool and useful info, thanks again @Mattias Burling!
In summary, what we have been discussing is the notion that any format has any special and unique look or characteristic: 'full frame look' and 'medium format look' really mean a 'shallow depth of field look' or in some cases 'swirly bokeh' or other lens artifacts, which aren't specific to any sensor size or any lenses designed for a specific format.

I am not making fun of anyone, we all are here to learn. If you don't give 2 shits, well we sure aren't going to debate, learn much being like that.  No one on here that I know is rolling in the dough or they probably would not be on here if they were.
I hope this forum is a learning experience, a place to see what others have tried, used, sold hated, liked. Even still have. There is no One camera. Even 60 million dollar films use Go Pros in them, BM cameras. They are throw away stuff for car chases, fire scenes etc. I want to see what works and what does not for people like us that we can afford... If you can get a Cine look out of a GH4 well show us how. Save us a shit pot full of cash.
Looks damn good. Trailers are always a bit too choppy, scene cuts out the ass to judge footage with, but I do like it. Would have to see the normal footage. There is a reason we are now up to a GH5 coming out. The GH1 was a breakthrough camera and it has gotten better with every new version.

@tupp I know you say you're serious however I've been saying it's the optics, and only the optics for this entire thread (this a quote of what I wrote from your post quoting me):
Are you even reading my posts lol?
So now we're in agreement that it's not sensor size, great!
Let's get on with debunking lenses designed for a certain sensor size format have special properties not present in lenses designed for other formats. You're going to need a large format camera vs. Super 16 in order to demonstrate the effect your propose is real? Why not use a cellphone vs. the World's Largest Camera? Yes I'm joking, to demonstrate the absurdity of all this
There are no significant looks or special properties for lenses designed for a specific format either. With the lens somewhat close to the subject I suppose size could matter, however there are full frame lenses bigger than medium format lenses so that's not it. What is it about medium format lenses (or large format lenses) that make them produce a unique look only available to those lenses? Can you show us examples demonstrating these unique qualities? That also means strapping a focal reducer to a medium format lens captures these special properties and makes them available to a full frame sensor? Any examples to share? (swirly bokeh as shown in this thread is also available with full frame lenses).
As with the sub-debate with @tupp, I've been saying it's the optics, and only the optics, for this entire thread. The debate was sensor size having an effect, or not.
Now the debate has moved to lenses designed for a specific format have some kind of unique properties only available to those lenses. What are these special properties, and where is the proof supporting this claim?

70mm film (actually 65mm, 70mm is marketing) provides a lot more resolution, so the projected image can be much bigger. Nothing special about the look other than marketing :P
I watched Interstellar in 70mm and it was kind of a mess (Chinese theater in Hollywood), with lots of blurry shots and overall not very sharp (+ sound was way too high and distorted). The 35mm shots were glaringly too sharp when they cut in. A while later I watched Interstellar again in 4K digital (AMC Century City) and it looked more consistent (maybe it was a new edit- they had fixed the sound problem). 70mm is a marketing term, generally telling us to expect a giant, high resolution screen (they may imply a special magical look, however that's just marketing going after your money).
The ARRI 65 is 3 ALEV III sensors rotated 90 degrees (A3X). This also provides a major boost in resolution. The ARRI look is at least partly due to the ALEV III sensor, and making one higher resolution with smaller pixels while maintaining the same look is likely challenging (though they may have solved it by NAB for a (true) 4K+ Alexa announcement).

'Look' works as it captures any possible effect at all. The argument has been: does sensor size, by itself, create any specific visual effect or look, whatsoever, or not.
Do lenses made for different formats have any special characteristics related to the intended capture format? One could argue size, however some full frame lenses are bigger than some medium format lenses. I had asked Brian Caldwell if he'd be making a medium format Speed Booster and he said no. There are now many very high quality full frame lenses and medium format lenses have no unique properties, so there was no point. A lens is defined by its optical transfer function, that's it.
In this thread we learned that some medium format lenses can be found for very low cost. Combined with a focal reducer for full frame bodies that provides a cost effective way to get shallow depth of field, swirly bokeh, or other desired artistic looks. That's cool and useful info, thanks again @Mattias Burling!
In summary, what we have been discussing is the notion that any format has any special and unique look or characteristic: 'full frame look' and 'medium format look' really mean a 'shallow depth of field look' or in some cases 'swirly bokeh' or other lens artifacts, which aren't specific to any sensor size or any lenses designed for a specific format.

Adding to the post from @jcs:
The FoV (or angle of view for photography/videography) relative to the sensor size and focal length is given by the following equations:
Horizontal FOV = 2 * arctan( SensorWidth / EffectiveFocalLength)
Vertical FOV = 2 * arctan( SensorHeight / EffectiveFocalLength)
Here is what happens when you move the camera relative to an object (Changing the FoV only keeps the transversed magnification constant to make the perspective changes easier to spot) : 

 

'Look' works as it captures any possible effect at all. The argument has been: does sensor size, by itself, create any specific visual effect or look, whatsoever, or not.
Do lenses made for different formats have any special characteristics related to the intended capture format? One could argue size, however some full frame lenses are bigger than some medium format lenses. I had asked Brian Caldwell if he'd be making a medium format Speed Booster and he said no. There are now many very high quality full frame lenses and medium format lenses have no unique properties, so there was no point. A lens is defined by its optical transfer function, that's it.
In this thread we learned that some medium format lenses can be found for very low cost. Combined with a focal reducer for full frame bodies that provides a cost effective way to get shallow depth of field, swirly bokeh, or other desired artistic looks. That's cool and useful info, thanks again @Mattias Burling!
In summary, what we have been discussing is the notion that any format has any special and unique look or characteristic: 'full frame look' and 'medium format look' really mean a 'shallow depth of field look' or in some cases 'swirly bokeh' or other lens artifacts, which aren't specific to any sensor size or any lenses designed for a specific format.

'Look' works as it captures any possible effect at all. The argument has been: does sensor size, by itself, create any specific visual effect or look, whatsoever, or not.
Do lenses made for different formats have any special characteristics related to the intended capture format? One could argue size, however some full frame lenses are bigger than some medium format lenses. I had asked Brian Caldwell if he'd be making a medium format Speed Booster and he said no. There are now many very high quality full frame lenses and medium format lenses have no unique properties, so there was no point. A lens is defined by its optical transfer function, that's it.
In this thread we learned that some medium format lenses can be found for very low cost. Combined with a focal reducer for full frame bodies that provides a cost effective way to get shallow depth of field, swirly bokeh, or other desired artistic looks. That's cool and useful info, thanks again @Mattias Burling!
In summary, what we have been discussing is the notion that any format has any special and unique look or characteristic: 'full frame look' and 'medium format look' really mean a 'shallow depth of field look' or in some cases 'swirly bokeh' or other lens artifacts, which aren't specific to any sensor size or any lenses designed for a specific format.

The concept of equivalence is a technical one, math and physics. The perception of specific looks is an artistic one. Here's APS-C, full frame, and medium format compared with equivalent settings (thanks @BTM_Pix , from https://***URL removed***/forums/thread/4125975 ):

Are the 3 shots pixel perfect? That's not possible 'in the real world' (via simulation it is easy if we don't simulate truly random noise). Consider that if you take two consecutive shots 'in the real world' with the same camera and lens and change nothing, the two shots can't be pixel perfect because of noise alone. The Earth rotates, clouds move, wind blows, etc. However as the photographer who did the test states, the images look more alike than different, and share the same look or character.
The argument has been that sensor size alone, which gives rise to special looks, such as 'the full frame look' and 'the medium format look' and 'the large format look' are specific and real, where the sensor size alone gives images a unique, identifiable character and specific look.
The actual looks or characters that people are really referring to are:
Shallow depth of field Lens artifacts, including bokeh 'style', highlight behavior, contrast, sharpness, color, distortion, defects, etc., as the lens is a kind of optical transfer function or filter, ranging from clinical and accurate such as Zeiss, to something wild like a Helios or Cyclop That's it, there is nothing more. Even with different cameras and lenses, when set up for equivalence, as in the above example, the average person can't tell which camera shot which image as they all have a very similar look or character when using lenses with similar characteristics. The fact that a focal reducer (Speed Booster) works as expected should be sufficient evidence that sensor size is not responsible for any specific look or character.
Photography and filmmaking are very technical forms of creating art. Everyone on this forum has the ability to do the simple math and set up their cameras for equivalence:
To get the full frame camera equivalent to the crop sensor camera:
Multiply the focal length of the lens by the crop factor Multiply the aperture by the crop factor Multiply the ISO by the crop factor squared. Example from my website http://brightland.com/w/the-full-frame-look-is-a-myth-heres-how-to-prove-it-for-yourself/:
Let’s do one using the A7S in FF and APS-C (Super 35) crop mode. The crop factor is 1.5. We’ll set up the camera as follows using the Canon 70-200 F2.8L II and the Metabones IV Smart Adapter:
Super 35 (APS-C mode on): 70mm, F2.8, ISO 800 Full frame (APS-C mode off): 70mm*1.5 = 105mm, F2.8*1.5 = F4.2, we’ll use F4, ISO 800*(1.5*1.5) = 1800, we’ll use ISO 1600

Can you tell which is full frame and which is crop without cheating or using a blink test? At the pixel level the images are different, however the overall look or character is considered the same.
Here's a friendly challenge to @tupp, @Mattias Burling, @Andrew Reid, and anyone else who feels that each format has a specific look which can be characterized:
Do your own equivalence tests Share the results online Do not label the images or filenames (so people can't cheat) See if anyone can identify which images are what format, and what are the specific characteristics which allow them to tell the formats apart If anyone needs assistance with the math or settings I can help and I'm sure there are others here who can as well. Remember I used to believe in the full frame look too until I did these tests.
Anyone wanting to continue arguing without doing these tests for themselves is either lazy, blocked by their ego, or just enjoys arguing. Nothing wrong with being any of those things, it's part of being human, however we won't be able to take you seriously in this scientific debate  

The concept of equivalence is a technical one, math and physics. The perception of specific looks is an artistic one. Here's APS-C, full frame, and medium format compared with equivalent settings (thanks @BTM_Pix , from https://***URL removed***/forums/thread/4125975 ):

Are the 3 shots pixel perfect? That's not possible 'in the real world' (via simulation it is easy if we don't simulate truly random noise). Consider that if you take two consecutive shots 'in the real world' with the same camera and lens and change nothing, the two shots can't be pixel perfect because of noise alone. The Earth rotates, clouds move, wind blows, etc. However as the photographer who did the test states, the images look more alike than different, and share the same look or character.
The argument has been that sensor size alone, which gives rise to special looks, such as 'the full frame look' and 'the medium format look' and 'the large format look' are specific and real, where the sensor size alone gives images a unique, identifiable character and specific look.
The actual looks or characters that people are really referring to are:
Shallow depth of field Lens artifacts, including bokeh 'style', highlight behavior, contrast, sharpness, color, distortion, defects, etc., as the lens is a kind of optical transfer function or filter, ranging from clinical and accurate such as Zeiss, to something wild like a Helios or Cyclop That's it, there is nothing more. Even with different cameras and lenses, when set up for equivalence, as in the above example, the average person can't tell which camera shot which image as they all have a very similar look or character when using lenses with similar characteristics. The fact that a focal reducer (Speed Booster) works as expected should be sufficient evidence that sensor size is not responsible for any specific look or character.
Photography and filmmaking are very technical forms of creating art. Everyone on this forum has the ability to do the simple math and set up their cameras for equivalence:
To get the full frame camera equivalent to the crop sensor camera:
Multiply the focal length of the lens by the crop factor Multiply the aperture by the crop factor Multiply the ISO by the crop factor squared. Example from my website http://brightland.com/w/the-full-frame-look-is-a-myth-heres-how-to-prove-it-for-yourself/:
Let’s do one using the A7S in FF and APS-C (Super 35) crop mode. The crop factor is 1.5. We’ll set up the camera as follows using the Canon 70-200 F2.8L II and the Metabones IV Smart Adapter:
Super 35 (APS-C mode on): 70mm, F2.8, ISO 800 Full frame (APS-C mode off): 70mm*1.5 = 105mm, F2.8*1.5 = F4.2, we’ll use F4, ISO 800*(1.5*1.5) = 1800, we’ll use ISO 1600

Can you tell which is full frame and which is crop without cheating or using a blink test? At the pixel level the images are different, however the overall look or character is considered the same.
Here's a friendly challenge to @tupp, @Mattias Burling, @Andrew Reid, and anyone else who feels that each format has a specific look which can be characterized:
Do your own equivalence tests Share the results online Do not label the images or filenames (so people can't cheat) See if anyone can identify which images are what format, and what are the specific characteristics which allow them to tell the formats apart If anyone needs assistance with the math or settings I can help and I'm sure there are others here who can as well. Remember I used to believe in the full frame look too until I did these tests.
Anyone wanting to continue arguing without doing these tests for themselves is either lazy, blocked by their ego, or just enjoys arguing. Nothing wrong with being any of those things, it's part of being human, however we won't be able to take you seriously in this scientific debate  

Yeah, they have been dangling the carrot for a long time!

And by a strange coincidence, a post has just popped up on DPR with an ad hoc equivalence test someone has done with MF,FF and APS-C.
As an aside, the amount of gear he seems to have had with him on a (presumably) non-photographic related business trip makes we wonder if he needs sherpas when he's going on a fully fledged shooting outing.
https://***URL removed***/forums/thread/4125975

This sums up the post-fact world we are currently living in beautifully!
 
No, but you'll more easily see the half tone pattern if you fill your field of view with it. Or, to put it another away it captures less ink. I don't know why you're getting into this analogy as what you're getting at relates to the explanation of why smaller sensors tend to be noisier. I don't think anyone has suggested that exposure changes with sensor size.
Well, it's not confusing or meaningless to me and to others who understand the principle of equivalence. I use it to calculate what focal length and aperture will be required to match field of view and depth of field when moving from one format to another. For that reason alone, it's worth developing a coherent understanding of it.
@tupp all those small differences in your AB comparison are of course accounted for by the things that you mention, entrance pupil distance, diffraction, etc. etc. These factors don't enter into equivalence calculations, nor do they contradict them. Their effect is so minimal as to be altogether invisible to the average viewer, despite their dramatic apparence to you. Relative to the changes in image wrought by changing focal length, aperture, or sensor size, their effect is negligible.
Equivalence is theoretically sound and empirically verifiable. I would encourage dissenters to investigate it more closely and carefully. What does it predict? Do the results match the predictions?

I love this forum for the fights that break out! Sometimes, I do wonder how much of it is down to trolling & how much is down to confussion over terminology.
The way i see it, is that there is no such thing as a "sensor look", what it we are really talking about is how a sensor transposes the qualities of a given lens to create a picture or image.
I have noticed this with the swirly bokeh madness created by the Helios 40-2 85mm f1.9: depending on how big the sensor is (FF, APS-C or s16mm), will have have an effect on how much of the lens circle the sensor will be able to use in order to take a picture. So, no matter what sensor/camera you use, you'll always get the insane swirly bokeh, because that is the LOOK that this lens produces.
So when you put the same lens on different sensor sizes, you're not creating a new LOOK, just a different focal lenth & interpretation of the lenses characteristics?
Shit, now I think I am confused!

Hey Mattias, if after everything I have posted, and everything Brian Caldwell, the designer of the SpeedBooster has posted, has not convinced you that there's no such thing as a full frame or medium format look, no worries. I wasn't trying to win an argument, only to share what I have learned with others. Have you tried working through the equivalence equations, setting up the camera and reviewing the results as I did here? If not, how can you dismiss it if you haven't tried it? If you have any questions about setting it up, feel free to PM me. It would probably make a cool video that a lot of people would be interested in seeing

Hey Mattias, if after everything I have posted, and everything Brian Caldwell, the designer of the SpeedBooster has posted, has not convinced you that there's no such thing as a full frame or medium format look, no worries. I wasn't trying to win an argument, only to share what I have learned with others. Have you tried working through the equivalence equations, setting up the camera and reviewing the results as I did here? If not, how can you dismiss it if you haven't tried it? If you have any questions about setting it up, feel free to PM me. It would probably make a cool video that a lot of people would be interested in seeing