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05-18-2014, 07:08 AM   #16
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I was aware of all this, but watched because equivalence is a pet peeve. The video was well made, I will be pointing others to it. (Especially m4/3 users, who mostly cannot seem to grasp equivalent aperture).

Unfortunately smaller sensor camera manufacturers will never change their misleading ways. Marketers are not known for their ethics. If we could only get reviewers to be accurate with equivalence, it would help immensely.

05-18-2014, 12:53 PM - 2 Likes   #17
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I just think the whole idea of equivalence seems to really make a situation that, up until the digital era of imaging, seemed to not be a factor at all. I mean, did medium format shooters try and calculate the "equivalence" of 35mm format when it was introduced? I seriously doubt it.

The optical properties of a lens stay the same no matter what sensor is capturing they image circle that is projected onto it. Yes, the area captured by the sensor (crop factor if you will) does influence how the image is framed and will therefore cause a different result due to the influence of the captured area on how the photographer makes their choice of focal length (affecting FOV) and their physical distance from the subject due to the crop factor of the sensor. Does this change how the lens will behave? No. That's all I was trying to get at before.

To me, there is no real "equivalence" In terms of the optical characteristics of a lens between formats. They will simply behave differently depending on format, most specifically in OOF rendering. To me this is an important point to make: if you are shooting with an MFT sensor camera, you cannot get the same OOF rendering (bokeh) effects that you will with an APSC or Full Frame sensor camera, simply because the crop factor requires using either a shorter focal length lens at the same distance from the subject, or the same focal length lens moved twice the distance from the subject. Both of these factors will change the OOF rendering of the captured image.

One last question: so, if aperture is also "converted" depending on crop factor, why, when I meter with my Gossen Lunasix Pro and use it's settings on my camera, do I still acheive correct exposure?

I get a feeling that the camera manufacturers adjust sensor gain to match benchmark ISO sensitivities so the metering is the same as a 35mm reference exposure. This is the only thing that makes sense to me- otherwise we'd all have to modify readings from an external exposure meter to get correct exposure depending on the crop factor of the sensor we're using.
05-18-2014, 01:53 PM   #18
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equivalence

Wow it took me 2 days and watching the video to get to the point where I may get it! I should leave well enough alone but one question. If you are using a full frame lens on an APS-C camera, is the APS-C picture is equivalent (exposure, depth of field,...) to a full frame picture except for the field of view? If it is, I get it, if it is not then will have to watch the video again......
05-18-2014, 03:55 PM - 1 Like   #19
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QuoteOriginally posted by TonyNorthrup Quote
Well, you might want to watch the video, because I do explain the physics. If you disagree with my math, just let me know where my math is wrong and I'll happily fix it.
Oh, so you're the author, nice from you to drop by. The issue is more fundamental than some math error; unfortunately I cannot point to a fix other than removing your video altogether. Sorry, I know it's your hard work and you had all the best intentions; but an universal "equivalence" simply cannot work. I will give you just some examples where it fails, instead of making an exhaustive list.

First, as a Pentax user I have no reason to relate to a format I'm no longer using; no, I don't have to multiply anything. Fail #1.

I've learned about focal length in high school, that's how elementary optics lessons starts. You're telling me that focal length "sucks", and I should not trust manufacturers for stating the real focal length on their lenses. It's not like you have a solution for the same lens being used on different formats, do you? Try to use m4/3, APS-C, FF and medium format lenses on a m4/3 camera, all marked with their native "equivalent focal length"; what a mess would that be. Fail #2.

Claiming that the same focal length should get you the same angle of view regardless of the format, something that focal length was never supposed to do. Then using this bogus claim to support "equivalence" - Fail #3.

ISO/sensitivity is not a measure of sensor noise. Claiming that it should be, without actually including any method of noise measurement (because sensors are using different technologies), then using this claim to support "equivalence" - Fail #4.

Claiming that aperture should measure DoF, something that it was never supposed to do; then using this claim to support "equivalence". Fail #5.

Even if you said several times that we're not dealing with film, but with digital cameras with different sensor sizes - with film, there were many different formats. Yet we all used real focal lengths, apertures and the ISO sensitivity. Fail #6.

And the icing on the cake: all those computations would be rendered useless if you crop&resize the image, effectively changing the "crop factor". You would actually need to compute some "equivalent" set of bogus things for every crop you'll make out of the same picture.
The markings on the lens would need to change real time, too.

05-18-2014, 04:51 PM   #20
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QuoteOriginally posted by virgilr Quote
One last question: so, if aperture is also "converted" depending on crop factor, why, when I meter with my Gossen Lunasix Pro and use it's settings on my camera, do I still acheive correct exposure?
He is equalizing for noise not exposure. The exposure will be the same, but the smaller sensor will produce more noise. Take 3200 ISO as an example. We can set and shoot for the same exposure, but the smaller sensor will display more noise at 3200 than the larger sensor all else being equal. Camera manufacturers fudge their ISO ratings a little bit. Just look at DxO. When you get into the higher end MF systems they tend to hold true to ISO rating and work fine with hand held light meters, but consumer and enthusiast cameras tend to fudge the numbers. My K-3 under exposes by 1/3 of a stop.

---------- Post added 05-18-14 at 07:09 PM ----------

QuoteOriginally posted by Hiroshi Quote
Wow it took me 2 days and watching the video to get to the point where I may get it! I should leave well enough alone but one question. If you are using a full frame lens on an APS-C camera, is the APS-C picture is equivalent (exposure, depth of field,...) to a full frame picture except for the field of view? If it is, I get it, if it is not then will have to watch the video again......
If you hold everything else constant (ISO/Shutter/Aperture) then you will get a different field of view, and the smaller sensor will have a lower signal to noise ratio (more noise). Of course the increase in noise might not be visible in final output. The smaller APS-C image has to be magnified more than the FF image and this will make the noise more visible and there is a compression effect caused by the magnification that will be visible in larger prints.
05-18-2014, 05:44 PM   #21
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QuoteOriginally posted by Winder Quote
Camera manufacturers fudge their ISO ratings a little bit. Just look at DxO. When you get into the higher end MF systems they tend to hold true to ISO rating and work fine with hand held light meters, but consumer and enthusiast cameras tend to fudge the numbers. My K-3 under exposes by 1/3 of a stop.

---------- Post added 05-18-14 at 07:09 PM ----------

Hang on. When I use my meter, I get very near the same exposure (center weighted on the camera, reflective metering on my meter which is from what I've read in the documention on the meter using the same center-weighted average calculations). It may vary by 1/3 stop, but this is a gossen lunasix without any type of sighting for reflective metering, so I can't say I'm 100% metering the same area, but I did two shots comparing the in-camera metering and manual mode using the meter readings. The calculated exposures from both metering methods gave the same histogram results in Lightroom.

I think this whole idea of equivalence is a bit tricky. One of the reasons why, in my first post, I questioned the presentation information regarding the two shots being compared and the OoF rendering was the fact that the presenter stated the full frame image was shot with a 200mm lens, and the MFT image was shot with a200mm lens. I didn't realize the "equivalence" calculation was being used to represent the focal length of the MFT shot. To me, that should NEVER be done - the focal length of the lens is a fixed value inherent to the lens. If I would have known this was the case, I would have realized that yes, the OoF rendering was different due to the fact that a 100mm lens was used in the MFT shot. But then again, the OoF would have been different if an actual 200mm lens had been used on the MFT, since to get the same framing the camera would have had to been much further away from the subject than with the FF camera.

When I shoot with my APSC body, I don't consider my lens to be 1.5x the focal length as stated on the lens. I think I'm cropping out a portion of the image circle. So I consider the characteristics of the lens and how that will affect my image.
05-18-2014, 05:44 PM - 2 Likes   #22
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QuoteOriginally posted by Kunzite Quote
First, as a Pentax user I have no reason to relate to a format I'm no longer using; no, I don't have to multiply anything. Fail #1.
You being a Pentax user has nothing to do it. Fail #1

QuoteOriginally posted by Kunzite Quote
You're telling me that focal length "sucks", and I should not trust manufacturers for stating the real focal length on their lenses. It's not like you have a solution for the same lens being used on different formats, do you? Try to use m4/3, APS-C, FF and medium format lenses on a m4/3 camera, all marked with their native "equivalent focal length"; what a mess would that be. Fail #2.
That's not what he's saying at all. You're completely missing the point.... Fail #2

QuoteOriginally posted by Kunzite Quote
Claiming that the same focal length should get you the same angle of view regardless of the format, something that focal length was never supposed to do. Then using this bogus claim to support "equivalence" - Fail #3
Where did he claim this? At what point in the video?

QuoteOriginally posted by Kunzite Quote
ISO/sensitivity is not a measure of sensor noise. Claiming that it should be, without actually including any method of noise measurement (because sensors are using different technologies), then using this claim to support "equivalence" - Fail #4.
That's not what he said.

QuoteOriginally posted by Kunzite Quote
Claiming that aperture should measure DoF, something that it was never supposed to do; then using this claim to support "equivalence". Fail #5.
Again. Not what he said.

QuoteOriginally posted by Kunzite Quote
Even if you said several times that we're not dealing with film, but with digital cameras with different sensor sizes - with film, there were many different formats. Yet we all used real focal lengths, apertures and the ISO sensitivity. Fail #6.
You are completely missing the point. The ASA/ISO standards was developed as a standard for sensitivity of film. Sensors don't operate the same way and we are dealing with digital gain, not sensitivity. Another point you seem to completely miss is that in the film days we didn't have so many lenses being used across so many different formats. Companies weren't designing for multiple formats with the same lens like they are today, so nobody really worried about equivalent FoV or performance. Companies didn't market lenses based on the 35mm equivalent. His point is that if companies are going to market the equivalent focal length to uninformed consumers, then they should also market the equivalent aperture. Since aperture is a function of focal length, you can't change the parameters of one and not change the other.
05-18-2014, 06:07 PM   #23
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An interesting article promoting the idea of forgetting all about equivalence.

Admiring Light - “Full Frame Equivalence” and Why It Doesn’t Matter

As far as MFT lens manufacturers marking a lens with it's "crop factor" focal lengths: Wrong. Absolutely wrong.

05-18-2014, 07:45 PM   #24
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I've come to the conclusion that m43 users are traumatized

QuoteOriginally posted by virgilr Quote
An interesting article promoting the idea of forgetting all about equivalence.

Admiring Light - “Full Frame Equivalence” and Why It Doesn’t Matter
That article has been derided a bit on dpreview as an m43-user's equivalence-denial rant

For example after some emails and prodding he seemed to flesh out the the difference between exposure and total light earlier in the article, but then later in the article he forgot it again when he claimed that a 75 f/1.8 lens on m43 is just as good as a 150 f/1.8 lens on FF, because, I guess, "sometimes you want more DOF wide open." I guess FF shooters are always looking to get that magical m43 DOF and they just can't figure out how to stop down

QuoteQuote:
As far as MFT lens manufacturers marking a lens with it's "crop factor" focal lengths: Wrong. Absolutely wrong.
I agree, because in terms of exposure (not total light) the F-stop remains the same, so changing it on the lens doesn't bring any more clarity to the photographer, overall - or rather it trades on confusion for another.

Plus it would just be rubbing salt in the m43 shooter's wounds.
05-18-2014, 10:17 PM   #25
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QuoteOriginally posted by jsherman999 Quote
That article has been derided a bit on dpreview as an m43-user's equivalence-denial rant

For example after some emails and prodding he seemed to flesh out the the difference between exposure and total light earlier in the article, but then later in the article he forgot it again when he claimed that a 75 f/1.8 lens on m43 is just as good as a 150 f/1.8 lens on FF, because, I guess, "sometimes you want more DOF wide open." I guess FF shooters are always looking to get that magical m43 DOF and they just can't figure out how to stop down



I agree, because in terms of exposure (not total light) the F-stop remains the same, so changing it on the lens doesn't bring any more clarity to the photographer, overall - or rather it trades on confusion for another.

Plus it would just be rubbing salt in the m43 shooter's wounds.
But if the manufacturers did advertise the adjusted aperture it would eliminate the exact problem you point out in your first post. The uninformed buyer who picks up the stellar 75mm f/1.8 and reads that it is the equivalent to a 150mm on a full frame, so he go around telling everyone that its just like a FF150mm F/1.8. There's a large number of buyers who have no idea what aperture is or how to calculate it.
05-18-2014, 10:21 PM - 1 Like   #26
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I found the contents of the video quite logical, but I fail to see the need to start arguing about it. I just got an explanation to something I had been wondering about and been too lazy to figure out myself. Then again, everybody has the right to believe in whatever he/she feels at home with. When collecting water in the rain the small and stylish bucket may indeed be more practical than the large, ugly and heavy one. It may take more time but it's much lighter to carry.
05-19-2014, 12:40 AM   #27
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QuoteOriginally posted by Winder Quote
You being a Pentax user has nothing to do it. Fail #1
Actually, it does. Not specifically being a Pentax user, but a non-135 format user; I don't need "equivalence", except maybe in the rare occasions I would want to compare two formats on paper. And even then it's unneeded, because the good, old methods are telling me all I want.

QuoteOriginally posted by Winder Quote
That's not what he's saying at all. You're completely missing the point.... Fail #2
Can't you see the big "ISO, Aperture, & Focal Length - Why they suck"? How about "Crop Factor with ISO & Aperture: How Sony, Olympus, Panasonic, Canon, Nikon & Fuji Cheat You"?
If I'm mistaken then please, explain to me what they really mean.

QuoteOriginally posted by Winder Quote
Where did he claim this? At what point in the video?
When he started comparing images taken with different formats and was amazed how they're not the same. It starts at 1:30, and by 1:44 it's getting interesting. To quote the author: "that doesn't makes any sense"; and he's claiming that focal length "doesn't work". Sorry for being blunt, but that is pure BS: the focal length always works, even if the lens is not put on any camera.
It's the "replacement focal length" that doesn't work, except in certain conditions; and it's even influenced by post-processing. How's that for an universal metric!

QuoteOriginally posted by Winder Quote
That's not what he said.
Discussion about ISO starts at around 3:35, and you can see on the screen: "For the pixel peepers: This covers overall image noise, not per-pixel noise, which has little practical impact the way most of us view images. I will cover pixel density and per-pixel image noise in a later video." And it's continuing on the same line, comparing the noise at different ISO.
Of course, you could say that he was only talking about "total light gathering" (another thing ISO isn't supposed to measure); but this is built around "overall image noise".

QuoteOriginally posted by Winder Quote
Again. Not what he said.
The discussion about "Aperture and DoF" starts at about 15:00. At 16:05 we have two images shot with the same aperture but on different formats; same story: DoF is different, and he's amazed about it.

QuoteOriginally posted by Winder Quote
You are completely missing the point. The ASA/ISO standards was developed as a standard for sensitivity of film. Sensors don't operate the same way and we are dealing with digital gain, not sensitivity. Another point you seem to completely miss is that in the film days we didn't have so many lenses being used across so many different formats. Companies weren't designing for multiple formats with the same lens like they are today, so nobody really worried about equivalent FoV or performance. Companies didn't market lenses based on the 35mm equivalent. His point is that if companies are going to market the equivalent focal length to uninformed consumers, then they should also market the equivalent aperture. Since aperture is a function of focal length, you can't change the parameters of one and not change the other.
No, I am getting the point - I just disagree with it. But it seems to me you are missing the points he's making and the implications (see above).

As I already said, if the companies would write on their lenses the "equivalent" aperture and focal length, the result would be chaos.
On compacts it works, but just because of two factors:
- people don't know nor care about sensor sizes, which actually are never precisely specified.
- the lens is fixed. That is, you can't take a 200mm lens, put it on your compact and wonder how it's much more "tele" than the integrated "750mm".

And I'll end up with yet another amazing quote from that video:
"Camera settings are kind of arbitrary and meaningless". EPIC FAIL, with decades of photography to prove it.
05-19-2014, 02:27 PM - 1 Like   #28
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QuoteOriginally posted by Kunzite Quote
Actually, it does. Not specifically being a Pentax user, but a non-135 format user; I don't need "equivalence", except maybe in the rare occasions I would want to compare two formats on paper. And even then it's unneeded, because the good, old methods are telling me all I want.
If you only intend to shoot one format your entire life, indeed 'equivalence' would be useless to you.

Many folks do shoot more than one format, though, or at least started with one format and moved to another - P&S to aps-c DSLR for example. Your P&S images really look different at 5mm than your aps-c images would at 5mm, no?



You're doing an equivalence conversion function in your head there, you need to. You just can't stop at FL and not include F-stop if you're interested in not kidding yourself. (the general 'you' btw)



QuoteQuote:
The discussion about "Aperture and DoF" starts at about 15:00. At 16:05 we have two images shot with the same aperture but on different formats; same story: DoF is different, and he's amazed about it.
He's not amazed about it, but a lot of people (read - a large portion of his target audience) are still truly amazed by that fact. Actual long-time photographers were struck by how their new aps-c digital images on the first Canon DSLRs seemed to have more DOF for the same FOV and F-stop back in the early '00s, to the point where they suspected the F-stop was 'lying' in their digital body. We still see people coming to this realization today.


.
QuoteQuote:
As I already said, if the companies would write on their lenses the "equivalent" aperture and focal length, the result would be chaos.
On compacts it works, but just because of two factors:
- people don't know nor care about sensor sizes, which actually are never precisely specified.
- the lens is fixed. That is, you can't take a 200mm lens, put it on your compact and wonder how it's much more "tele" than the integrated "750mm".
On fixed-lens small-sensor systems, it would be great and truthful if they did put the equivalent information on the lens face. I don't expect it to ever happen.

And m43 sells a lot of lenses because they look very tasty when the specs are flaunted, like "75mm f/1.8". Many m43 enthusiasts want to believe.





That leaves it up to us to spread the word in the face of the shadow institutions and vast, interconnected cover-ups. Are we up to the task?



.

Last edited by jsherman999; 05-19-2014 at 02:48 PM.
05-19-2014, 03:08 PM   #29
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No, I won't use equivalence even if I would go "FF". I just don't need it.

Putting the wrong focal length on compacts but leaving aperture and ISO works, because people are only interested in angle of view. Then, there's the practical issue: no manufacturer would want to be the first, to try and sell cameras with f-numbers so much higher than the others and ISOs so much smaller. Let's get real: "equivalence" is unenforceable.

No, he's stating his amazement instead of educating people. It's the exact opposite of what an experienced photographer should do when teaching people; he's lowering himself to the "average Joe who doesn't know about focal length" level.
And FTR, we had many more formats with film, than today with digital yet nobody was confused. If anything, we didn't had internet experts to teach us about "equivalence" and make simple things more complicated.

You're avoiding the obvious issues, so I'll try again: let's say I have an Olympus m4/3 camera with the 75mm f/1.8, and a Pentax APS-C with the APS-C only (?) Pentax 50mm f/1.8 and a FF Pentax 77mm f/1.8.
I will use the APS-C 50mm and the FF 77mm on the Pentax camera. I will also use all 3 lenses, m4/3, APS-C and FF, on the Olympus.
Now, the funny part: I also have a permanent marker and want to write the "equivalent" values on each lens. What should I write?
05-19-2014, 04:33 PM - 2 Likes   #30
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QuoteOriginally posted by Kunzite Quote
No, I won't use equivalence even if I would go "FF". I just don't need it.

Putting the wrong focal length on compacts but leaving aperture and ISO works, because people are only interested in angle of view. Then, there's the practical issue: no manufacturer would want to be the first, to try and sell cameras with f-numbers so much higher than the others and ISOs so much smaller. Let's get real: "equivalence" is unenforceable.
Honestly, i was trying to resist saying anything but seriously, what is with the negativity? you made a list of the number of things that are wrong with the video? So what? Someone made a nice video (all be it dumbed down a bit) which explains to ppl who are totally baffled by the concept how equivalence works. Ok maybe its not super technical (or technical enough to meet your standards) but geez do you maybe think that you are not the target audience? If you are mechanical engineer who specializes in say fluid dynamics you dont go around the basic "what is engineering" websites and cry about how they are riddled with tiny technical inaccuracies. you go to the journals and read information which is at your appropriate technical level. if he made this video any more technical he would have lost the audience in the first 5 minutes. besides, yes maybe he gives a few opinions here and there that maybe manufactures tend to mislead users with apertures. so what? geez. its an opinion. youtube is full of those. non the less this video is probably 90% positive information and maybe 10% mis-information. it has great visual examples which i think is hugely lacking online when ppl explain this concept. most ppl who have no idea about the subject will be better off and will have learned something at the end of the day. those who can already point the inaccuracies dont lose/gain anything. he doesnt need to TAKE IT DOWN.

besides seriously, if equivalence doesnt matter to you or "you dont need it" why do you bother going into a thread that talks about it and and try to shoot down other ppl's attempts at adding some value to the topic/helping newbies. dont be so negative and if you dont like it, make a better video.
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