[normhead]

From my reading of it, it's more of a lens usage thing. If you use lenses you should probably at least understand the basic concept. Of the factors that influence on DSLRs one of the factors is pixel pitch, so on film that would be one less variable to worry about, so maybe even more relevant on film. Also more relevant on film because of the difference in sensor size between 110 and 4x5 with your 75mm lens going from an ultra telephoto to a wide angle, for the same focal length. You need to at least understand that's going to happen.

[OregonJim]

Except where you're capturing half the light because your sensor is half the size and you have to blow your image up to twice the size to get the same sized image

I don't have to blow it up twice as much - I'm at 24MP already. The FF would have to be 48MP for that to be true. I'm not capturing half the light, either - the light intensity falling on both sensors is exactly the same, the larger sensor simply captures a wider fov.

Anyway, I don't want to fall down this silly rabbit hole again. That's what I get for browsing the threads while dinner is cooking.

[normhead]

I don't have to blow it up twice as much - I'm at 24MP already. The FF would have to be 48MP for that to be true. I'm not capturing half the light, either - the light intensity falling on both sensors is exactly the same, the larger sensor simply captures a wider fov.

Anyway, I don't want to fall down this silly rabbit hole again. That's what I get for browsing the threads while dinner is cooking.

And honestly, it doesn't really get you anything, unless you're interested in minutia, which while admittedly are of major importance to a select few, are often overlooked by the vast majority.

[JimmyDranox]

Few years ago, Canon has build a 1 Mp CMOS sensor. A one Mp sensor with active surface of 8x8''. Yes, a 200x200mm sensor, for only one Mp. Now, this sensor is used in a astronomy observatory for making movies of 19 magnitude stars. Maybe this problem which is debated here, is no issue for those Canon engineers.

AFAIK, the bigger pixel size, the sensibility is bigger, and the noise is smaller. Simple.

[easyreeder]

Few years ago, Canon has build a 1 Mp CMOS sensor. A one Mp sensor with active surface of 8x8''. Yes, a 200x200mm sensor, for only one Mp. Now, this sensor is used in a astronomy observatory for making movies of 19 magnitude stars. Maybe this problem which is debated here, is no issue for those Canon engineers.

AFAIK, the bigger pixel size, the sensibility is bigger, and the noise is smaller. Simple.

I like the ff lenses, and I like the idea that I'm getting all I can out of them. But alas, I'm not getting all the image or all the light from the FF lenses. The lens will not change the size of the sensor. Some of the image, some of the light, will not be utilized by the smaller sensor. That said, of course a smaller sensor can have great software etc. It just seems like, at this point, the easiest way to get the performance of a full frame sensor is to use a full frame sensor.

[jsherman999]

(from Norm's quote):



So, all of my lenses are designed for a FF (35mm) system. I use them on my K-3. Therefore, the whole equivalence argument goes out the window, because the advantage is all in the FF lenses, according to the FF proponents. But I'm already using the SAME LENSES, so I get all the 'equivalence' advantages on my APS-C sized sensor. Don't you guys see the folly in the whole theory?

You're not understanding what Joseph James was saying there, and a lot of people make this exact same mistake so I'm not picking on you - here's the quote for reference, then I'll explain:

"...In short, the advantage of a larger sensor system over a smaller sensor system is that the larger sensor system will generally have lenses that have wider aperture (entrance pupil) diameters for a AOV (diagonal angle of view) than smaller sensor systems, which allows for more shallow DOFs (as an option, not a requirement) and will put more light on the sensor for a given exposure, resulting in less noise..."

Note the 'wider aperture diameters for a AOV' - he's talking about the linear aperture, the entrance pupil, not the f-stop, for a given AOV.

Remember, the linear aperture (entrance pupil when you look down the front of the lens) is related to the F-stop with this formula:

FL / f-stop = entrance pupil diameter (linear aperture)

So, for a 50mm f/1.8 lens, wide-open we have:

50 / 1.8 == 27.8mm entrance pupil

Now, for the same AOV on, say, micro-4/3, we have to use a 25mm lens, so say we have a 25mm f/1.8 lens available:

25 / 1.8 == 13.9mm entrance pupil

So, for the same AOV & distance to subject, even though we're using the same F-stop and getting the same light density (exposure) allowing the same shutter speed, the larger sensor is getting more total light due to the wider aperture diameter (27mm vs 13mm.) This results in less DOF, and less photon shot noise** for the larger sensor in that comparison.

Make sense?

To bring it home, a basic equivalence quiz: looking at the formula above, what f-stop would be needed on a 25mm micro 4/3 lens to match the 50mm 1.8 on FF?

.
** Note, photon shot noise - not total noise - total noise is determined by shot noise, read noise, and sensor efficiency. So for example, a given m43 sensor with much greater efficiency and much less read noise than a given FF sensor could show less total noise in the image, even though the FF sensor starts out with lower shot noise.

[Big Dave]

Like many above, I have a nice collection of FF legacy lenses. I really like using them as intended. The fantastic high ISO performance of my Sony A7 is nice to, as well as the ability to mount just about any lens on the planet. If you haven't tried a hi-res EVF with focus peeking, you are missing a real treat. The A7 is great, but I still love my K5 II.

[ElJamoquio]

That's absolutely correct.
That's why FF lets people produce those highly coveted one eye in focus portraits.

You should take more portrait shots.

The only way one eye is in focus is if you're taking a picture of a nostril.

---------- Post added 06-13-14 at 09:46 PM ----------

I'm not in the mood of going through another "equivalence" discussion with you, knowing that it's pointless of doing so. I will only say this: all forms of "equivalence" are lying about something. Perhaps they're lying about what focal length is, or maybe just about using a set of 5 parameters to compare between formats.

Did equivalence insult one of your family members?

[jsherman999]

My source....
Equivalence.

You know, Norm, I've been quoting that article to you for probably over two years now, and I've tried to make probably every one of those bullet points to you at various times. Sometimes it's just easier to hear from another source, huh?

.

---------- Post added 06-13-14 at 11:16 PM ----------

So is lens equivalency strickly a digital thing and not applicable to film cameras?

It's fully applicable to film cameras as well. The physics is the physics. It never came front n' center as a concept back then because 1) we never really had film cameras with different film sizes sharing mounts/lenses, like we do with aps-c and FF sensor cameras, and 2) There was no internet in the same sense and degree prior to the DSLR age, and the iterations of discussion happened much slower, and comparisons (and questions about what you were seeing) happened in islands, cut off, unlinked and not-reference-able.

The concepts were reportedly known out there, though, just not carrying a catchy single label. (I've noticed naming something always gives it legs, makes it less amorphous, wraps it up in a bow.)

As I said, Joseph Wisniewski has said he was telling people about focal length and f-stop conversion ratios between large, medium and 135mm film formats back in the day. That was equivalence.

.

[Iberia]

This might help:



Angle of View Abbreviated as AOV.
The angle extending out from a lens along the path of what the camera can see.
It is worth noting that while focal length affects the field of view, the sensor size also affects Angle of view.
For example, a 100mm lens with a 35mm sensor will yield a wider AOV than the same lens with a 23mm (APS) sized sensor.
See the image below for a graphical depiction of this.



100mm Focal Length on Full Frame (left) and APS-C (right)





Field of View Abbreviated as FOV.
The rectangular area describing what the camera can see at a particular focus point.
This is similar to AOV except it describes the rectangular area at the focal point, so the FOV increases/decreases correspondingly with an increase/decrease of the focal point.
Because FOV is associated with AOV, it too is affected by sensor size.



source: Studiography - The Study of Studio Photography: September 2010



P.S.: some of you might be too young to remember but there used to be an APS "film" format before the advent of digital photography but the frame was 25mm wide, not 23mm like the "digital" APS-C

[Kunzite]

Did equivalence insult one of your family members?

Not unless Optics, Common Sense and I are family.
It's amusing when one is assuming a strong emotional involvement on the other side only, when he himself has an agenda (e.g. to "prove" FF is cheaper) and is emotionally involved in this matter. My only involvement is, however, just a reaction against this "equivalence in any form and circumstances is good" propaganda.

jsherman999: physics is me being able to (approximately) measure the focal length of a lens using a LED pointing device and a ruler. Making assumptions and even twisting the meaning of basic optics notions (said focal length) is not physics.
In other words, "equivalence" is lying by pretending to be physics when it's not. Don't believe it!

[Pål Jensen]

Did equivalence insult one of your family members?

There is no "law of equivalency". The only objective equivalency is based on the numbers printed on the manufacturers lenses. The "equivalency law" is based on biased opinion where you take only the properties that fits your preconceived ideas into consideration and disregard everything else.
In addition, it mixes up lens properties with properties defined by what you put behind the lens; this isn't an apple and oranges comparison - it is and apple and orange mixture. No wonder people get confused when trying to make sense of it and don't have a clear understanding of differences between focal lenght and angle of view; DOF and bokeh, not to mention have clear grasp of physics of exposure.

[Rondec]

Equivalency as stated by most people is actually wide open equivalency. That is to say, comparing lenses at only their widest apertures. If you happen to be one of those unfortunate souls who don't do that then, the formulas become less meaningful.

[Pål Jensen]

It's fully applicable to film cameras as well. The physics is the physics. It never came front n' center as a concept back then because 1) we never really had film cameras with different film sizes sharing mounts/lenses, like we do with aps-c and FF sensor cameras, and 2) There was no internet in the same sense and degree prior to the DSLR age, and the iterations of discussion happened much slower, and comparisons (and questions about what you were seeing) happened in islands, cut off, unlinked and not-reference-able.
.

1) Yes we did. We had APS cameras in the film days. In addition Pentax 645 and 67 lenses could be used on 35mm and Pentax 67 lenses could be used on the Pentax 645 body. There was lots of discussion about this a crop factors. But no equivalency nonsense.
2) We had internet about a decade before digital made a major impact.

---------- Post added 06-14-14 at 02:01 PM ----------

Equivalency as stated by most people is actually wide open equivalency. That is to say, comparing lenses at only their widest apertures. If you happen to be one of those unfortunate souls who don't do that then, the formulas become less meaningful.

Exactly.
It is based on the fact that for lenses with simliar speed and angle of view the larger format camera will have to shot at a slower shutterspeed at the same DOF.
So the FF shooter can say to the APS shooter: "Hey, wide open at 1.4 I have thinner DOF that you can get on yor 1.4 lens. So you need a faster lens to match mine DOF-wise".
However, the APS shooter can say; "Hold your fire, my lens can give images DOF-wise you can't with your camera. I have more DOF and also higher maximum magnification so I can make images you can't DOF-wise".
Who is right? Both are, and taking one side and make a law from it is nothing but a biased opinion. It is no law as it is purely subjective.

All you do when increasing or decreasing the fomat while maintaining the angle of view is transposing the DOF scale towards thinner or deeper DOF. Which scale is "correct" is purely a subjective issue. Theres no meaningfull law to be had from this - just preferences.

In addition, the wide open equivalency law treat the matter as if the function of fast lenses is thin DOF. This is not true. The function of fast lenses is to let in more light. Thin DOF is a secondary propertie due to the laws of optics. For those who do not take images wide open due to DOF, which is about 99% of us, the "law of equivalence" has no relevancy. A law needs to have relevance for everybody. Exposure, however, has relevance for all photographers and thats the real equivalency.

The Pentax FA645 45/2.8 mounted on a K-mount camera is fully equivalent to a hypothetical FA 45/2.8 on a K-mount camera. Thats why both are labeled 45/2.8 by the manufacturer. It isn't at all confusing.

[normhead]

1) Yes we did. We had APS cameras in the film days. In addition Pentax 645 and 67 lenses could be used on 35mm and Pentax 67 lenses could be used on the Pentax 645 body. There was lots of discussion about this a crop factors. Nothing has changed.
2) We had internet about a decade before digital made a major impact.

---------- Post added 06-14-14 at 02:01 PM ----------



Exactly.
It is based on the fact that for lenses with simliar speed and angle of view the larger format camera will have to shot at a slower shutterspeed at the same DOF.
So the FF shooter can say to the APS shooter: "Hey, wide open at 1.4 I have thinner DOF that you can get on yor 1.4 lens. So you need a faster lens to match mine DOF-wise".
However, the APS shooter can say; "Hold your fire, my lens can give images DOF-wise you can't with your camera. I have more DOF and also higher maximum magnification so I can make images you can't DOF-wise".
Who is right? Both are, and taking one side and make a law from it is nothing but a biased opinion. It is no law as it is purely subjective.

All you do when increasing or decreasing the fomat while maintaining the angle of view is transposing the DOF scale towards thinner or deeper DOF. Which scale is "correct" is purely a subjective issue. Theres no meaningfull law to be had from this - just preferences.

In addition, the wide open equivalency law treat the matter as if the function of fast lenses is thin DOF. This is not true. The function of fast lenses is to let in more light. Thin DOF is a secondary propertie due to the laws of optics. For those who do not take images wide open due to DOF, which is about 99% of us, the "law of equivalence" has no relevancy. A law needs to have relevance for everybody. Exposure, however, has relevance for all photographers and thats the real equivalency.

The Pentax FA645 45/2.8 mounted on a K-mount camera is fully equivalent to a hypothetical FA 45/2.8 on a K-mount camera. Thats why both are labeled 45/2.8 by the manufacturer.

What you need to know about equivalency...
If you know "what is a wide angle lens, what is a standard lens, and what is short and long telephoto, and that the larger the format, the longer lens you will use in each category, which also means shallower DoF is possible, you know enough. As pointed out in the article I posted, there are so many factors that in any individual case, your results will vary. You don't need formula, you can see the effects looking through the viewfinder, and you have to do that, whether you've done the math or not. It's pretty much a pastime that some use to amuse themselves. Not only that, people who don't care about it, can be more effective actually employing it, than people who claim to know the theory. Knowledge is not linked to practical application, to the point that I've never heard of it being employed in the field.

I've never heard. "It was a really tough shoot last night, I was losing my light, my model was grumpy and I was really having trouble getting my equivalency calculations to work out." No one ever says that.

It's the pet rock of armchair photographers.