Aren't we just confusing ourselves?

[OldClicker]

When we talk about different sensor sizes we start getting into 'virtual this' and 'equivalent that', aren't we just adding confusion? The way I see it, the sensor (or film) size does not change the characteristics of the lens or the shot. The only change is the amount of the image that hits the sensor and HOW WE REACT to that change in the field of view. No matter what the sensor/film size - if we use the same lens, from the same distance and print the same image (i.e. crop the larger one) of the same size (i.e. 8x10), nothing changes. If we change one of the above, then we should know how that change affects the final print, not say that the sensor size produces an ‘effective something or other’. Make sense? - TF

[CaraRose]

I think it's partly a semantic issue, partly an adjustment to new technology and changes.

Before our fancy schmancy aps-c digital SLR's, focal length was a description that belonged to the lens. In general, if I looked though any two cameras with a 50mm lens, I would see the same field of view.

But with the crop sensors, if I look through lens and see a different field of view than if I look through the same lens on a full frame. The fact that it's a crop of the same focal length is somewhat irrelevant, because I can't see the full focal length, I just see the crop. To my eye, one looks like a longer focal length than the other.

I think someone who only shot with an aps-c camera would have less of a problem wrapping their head around it. 32mm lens will give them the field of view they expect. But I learned shooting film, so my concept of the field of view I should see at 32mm is not what I see in my DRebel. To me it looks closer to 50mm. Is it? No. But from my perspective, it appears to be.

[Franglais]

I always talk about the view you get through a lens - "normal", "wide-angle", telephoto", etc. But it's handy for everyone, including the marketing guys, to be able to quantify it and focal lengths on a 24x36 film is the only standard.

For instance, both 28mm and 35mm are "wide-angle" views but the difference between them is significant. For ages point-and-shoot digital cameras had zoom lenses that only went as far as the 35mm view - and frustrated a lot of users. When the manufacturers finally got down to a 28mm view, saying it was "wider-than-wide" sounds like nonsense wheras saying it's the equivalent of a 28mm makes sense to some people.

[Frog]

I get the crop factor and know what it does and other than that, don't pay too much attention as its still 'what you see is what you get'. Most of the time I can back up or move forward to get what I want if the lens doesn't.
The thing that makes me consider full frame sensor is the better image quality, especially dynamic range. Out of my pocket books range for now though so I just do the best I can with what I have.

[OldClicker]

I think it's partly a semantic issue, partly an adjustment to new technology and changes.

Before our fancy schmancy aps-c digital SLR's, focal length was a description that belonged to the lens. In general, if I looked though any two cameras with a 50mm lens, I would see the same field of view.

But with the crop sensors, if I look through lens and see a different field of view than if I look through the same lens on a full frame. The fact that it's a crop of the same focal length is somewhat irrelevant, because I can't see the full focal length, I just see the crop. To my eye, one looks like a longer focal length than the other.

I think someone who only shot with an aps-c camera would have less of a problem wrapping their head around it. 32mm lens will give them the field of view they expect. But I learned shooting film, so my concept of the field of view I should see at 32mm is not what I see in my DRebel. To me it looks closer to 50mm. Is it? No. But from my perspective, it appears to be.

So if you go out with a 32mm prime with the film body and then the next day to get the same shot with the APS-C body, you would just back up, right? Seems to be a lot simpler to know all the things that change the image when you back up (since we have to know this anyway) than to remember a whole set of ‘virtuals’, ‘effectives’ and ‘equivalents’ for each sensor/film size. - TF

[opus]

I would think it would matter when choosing which lens to buy. If I see a lot of images I like that are taken with, say, a 75mm focal length lens, so I go out and buy one and put it on my camera, and the focal length that I get isn't the same as what I was expecting, I would be disappointed.

I bought my first L lens based on a recommendation from someone else. I admit I didn't spend enough thought on what focal lengths I prefer to shoot at. I am finding myself getting upset with my lens every single time I shoot, because I am not getting what I expected. I position myself where I am comfortable, and can't get "close" enough. I crop nearly everything I shoot. I've recently upgraded from a digital rebel to a 5D.

Perhaps the one who recommended the lens did not have a full-frame sensor like I do, and therefore gets "closer" than I do, and thus feels the lens is perfect. (I do love how wide it gets, though! But the majority of my shooting is generally not of the wider-angle type. I'm just not used to seeing that way.)

I'm NOT a gear head. I don't remember specs to save my life.

I might be sounding like a total ignoramus here ...

[Old Timer]

All I know is I shot 35mm film for years and when I went to a DSLR with 1.5 crop factor I had no trouble adjusting. I was disappointed the I didn't have the same great view with my 24mm that I use to, but thrilled that my 200mm now gave me an automatic crop to look like a 300mm for my sports shots. However when I got a full frame DSLR (D700) it was like waking back into an old familiar house where I knew where every room was and what it was used for. Did I have trouble making the transition back? No not at all. Now I just covet longer glass.

[AgingEyes]

When we talk about different sensor sizes we start getting into 'virtual this' and 'equivalent that', aren't we just adding confusion?

I guess not. In fact, if it says: "equivalent to 24mm of the 24x36mm", then I will have an idea what I will be seeing, what field of view I will be seeing through my crop factor DSLR viewfinder because I am used to the 28 of my film day. So by saying "equivalent to 28mm", it is telling me that although the focal length of the lens that I am using is a 17mm - which will never change, my photograph will looks like one that I will get if I am using a film camera with a 24mm lens on it like I did in the film days.

Now, for those who grew up with crop-factor digital camera, or old enough but have never shot 135 film cameras, then it may be confusing. I don't know

[opus]

They should start giving measurements kinda like you get on a computer monitor or tv screen. You know, like 17" or 27" .... I have no idea how you could do that, but there should be a way ...

I get what you mean by focal length. The image is still exactly as "far away" from me no matter which camera body I'm using. The difference is how much of a -- for lack of a better term -- "wide angle" you're seeing. How much of the picture you're going to see when you look through the lens. There should be a technical term for that which is understood by all. Again, I don't know how.

[opus]

Now, for those who grew up with crop-factor digital camera, or old enough but have never shot 135 film cameras, then it may be confusing. I don't know

I shot 35mm between 1983 - 1986, primarily. After that I pretty much used a little Kodak P&S until 2000, when I bought a Rebel film camera. Used it like a P&S until I got my DRebel.

Back in 1984 I was very skilled in the use of a 35mm camera. But in the 15 or so years after that, I forgot a LOT of things. It's only this year that I've specifically gone looking to reacquaint myself with the things I'd forgotten. Focal length is one of those things. What's confusing is, back in the days of film only, this wasn't even a question. In the past five or so years, I've never really delved into trying to understand what the question even meant. "What, something about an x-factor magnification scale? Sounds like algebra to me, no thank you!"

[OldClicker]

They should start giving measurements kinda like you get on a computer monitor or tv screen. You know, like 17" or 27" .... I have no idea how you could do that, but there should be a way ...

I get what you mean by focal length. The image is still exactly as "far away" from me no matter which camera body I'm using. The difference is how much of a -- for lack of a better term -- "wide angle" you're seeing. How much of the picture you're going to see when you look through the lens. There should be a technical term for that which is understood by all. Again, I don't know how.

It's Field of View, isn't it? - TF

[opus]

It's Field of View, isn't it? - TF

Now that you say it, it sounds familiar. How is that measured and communicated?

[AgingEyes]

Focal length is one of those things.

If you are using a 17mm lens, it is still a 17mm lens no matter if you use it on a 135 film camera, a full-frame DSLR or a non-full-frame DSLR. And what is a full-frame? It's the size of a 135 film. So there. The 135 film size is the reference standard that is being used.

What's confusing is, back in the days of film only, this wasn't even a question.

Not when you also shoot medium or large format though. In 135, a "standard" lens is 50mm but around 90 in medium format, if I remember correctly (I have a Mamiya 6x7RB).

[AgingEyes]

Now that you say it, it sounds familiar. How is that measured and communicated?

I guess angles and trigonometry have something to do with it

[another view]

All I know is I shot 35mm film for years and when I went to a DSLR with 1.5 crop factor I had no trouble adjusting.

I'm guessing this has to be the reason that they did it (for the record, I agree with the rest of OT's post and this has been my experience too, etc). I figured terms like "1.5x" and "equivalent" would go away before long, much like the 35mm bodies they replaced. They're still very common, and it's sort of funny that "full frame" is now getting more common.

[Frog]

I don't have any trouble multiplying by 1.5 to know what my lens is equivalent to.
Might have a bit more multiplying by 1.6.

[straightarm]

If you were used to full frame 35mm, most likely from film, then the conversion factor is useful, esp for wide angle work.

Otherwise, it's a case of working out a "standard" focal length for your chosen format and going on from there.

[Skyman]

This is a semantic argument as the numbers we use to describe focal length actually describe field of view (see the wikipedia entry on focal lengths) but since a given lens can have multiple fields of view based on the camera it is attached too, a new language needs to be developed over time. At the moment that language is 35mm equivalent, so smaller sensor sized cameras are commonly reffered to as having a magnification factor. In theory the same could be said about medium format with its crop factor expressed as a fraction, but most medium format users are used to this difference and know that an 85mm lens will produce results similar to a 50mm lens on a 35mm camera. Over time as formats stabilise and marketers come to grips with their products better, the language we use will simplyfy but for now refering to a magnification factor or a 35mm equivalency is fairly straightforward.

[opus]

excellent post, skyman

[CaraRose]

So if you go out with a 32mm prime with the film body and then the next day to get the same shot with the APS-C body, you would just back up, right? Seems to be a lot simpler to know all the things that change the image when you back up (since we have to know this anyway) than to remember a whole set of ‘virtuals’, ‘effectives’ and ‘equivalents’ for each sensor/film size. - TF

The assumption here is that you CAN backup.

I remember when I was shooting film, taking a shot of Juney Wank falls with my tripod leg on the very edge of trail (if I had tapped that sucker wrong, my Minolta would have been taking a steep dive down), and zoomed all the way out to get the photo. I think I had a 35-80 zoom on there. If I was in the same place trying to get the same shot with a 35mm lens on my Rebel, it would not be physically possible to get the exact shot. There was nowhere else to go except off the cliff. Unless I learned to fly, anyway... which I hear is just the knack of throwing yourself at the ground and missing, but I don't think I'm up to trying that :P

Your same argument can be reversed too... Let's say your in yellowstone taking shots of a bison. To get the same shot at 50mm as 300mm, taking your argument is to say 'just get closer'. But unfortunately this is a good way to get gored... as numerous people learn every year. I can take the shot at 50mm and crop in, but a crop of that magnitude is going to lose quality.

That said, does anyone actually remember a set of virtuals? Since I know what 35mm looks like through a film camera, if I want to know what whether my lens will have the approximate field of view to what I know is 35mm, I know my sensor has a 1.6 crop, then I either divide 35 by 1.6, or take actual focal length of my lens and multiply that times 1.6. The only reason for this is translate it to something that fits my perception of what 35mm should cover. I don't need to know anything else. This is just to give myself a guide.

Doing that, I can look at my 18mm-55mm zoom, and go to the Smokies this July and attempt to replicate the same shot of Juney Wank, because I know I'll have the same coverage.

[Loupey]

As much as I would like to tell people "accept what a 50mm gives you on your (fill-in-the-blank) camera and stop trying to determine the full-frame equivalent", I can see why it will be with us for a while.

The smaller format hasn't been standardized so a prospective buyer looking at Canon, Nikon, Olympus and the like are using the "equivalent values" for comparison purposes and to make their final choices. I still recommend that once the decision has been made that people start thinking of focal lengths in their respective formats.

As Skyman touched on earlier, when we shot medium format, we saw the world in the focal lengths that were appropriate for those formats. Switching between medium format and 35mm film was just a mental shift which became second nature.

One can continue forever trying to convert one convention into another or just accept it for what it is. Tough sell since we still haven't converted to the metric system like the rest of the world

[jetrim]

Now that you say it, it sounds familiar. How is that measured and communicated?

Field of view (or angle of view) is measured in degrees/minutes (fractions of degrees, not time).

For instance:

28mm - 74°

50mm - 46°

85mm - 28° 30'

200mm - 10° 20'

And it seems to me that this would be a much more accurate way of describing a lens' capability as it remains constant, like focal length. All manufacturers list this information already and websites such as B&H and Adorama show it under "details" if one bothers to look, though I expect few people do.

[OldClicker]

This is a semantic argument as the numbers we use to describe focal length actually describe field of view (see the wikipedia entry on focal lengths) but since a given lens can have multiple fields of view based on the camera it is attached too, a new language needs to be developed over time. At the moment that language is 35mm equivalent, so smaller sensor sized cameras are commonly reffered to as having a magnification factor. In theory the same could be said about medium format with its crop factor expressed as a fraction, but most medium format users are used to this difference and know that an 85mm lens will produce results similar to a 50mm lens on a 35mm camera. Over time as formats stabilise and marketers come to grips with their products better, the language we use will simplyfy but for now refering to a magnification factor or a 35mm equivalency is fairly straightforward.

Except that field of view isn't the only change that takes place when you move or zoom as a reaction the the sensor/film size. Do you have a crop factor for the DoF change? An 'effective DoF'? - TF

[Skyman]

Except that field of view isn't the only change that takes place when you move or zoom as a reaction the the sensor/film size. Do you have a crop factor for the DoF change? An 'effective DoF'? - TF

I agree totally if you change your focal length or position to compensate for a change in sensor size, but if you simply take a given lens and change it from one camera to the next the depth of field doesn't change, all you are changing is how much of the image circle hits the sensor / film.

[OldClicker]

I agree totally if you change your focal length or position to compensate for a change in sensor size, but if you simply take a given lens and change it from one camera to the next the depth of field doesn't change, all you are changing is how much of the image circle hits the sensor / film.

That's true and what I said above. It's not until you react to the change in sensor size that things change and most every characteristic of the optics does change. So, shouldn't we learn the results (all of them) of our reaction instead of trying to have a fudge factor for each. - TF