Bloke Loc: Waynesboro, Pennsylvania

I just got thinking last night... There are hundreds of lenses for sale - I mean lens *lines*, of course! - so I wonder if *all* the quoted focal lengths are "35mm equivalents". For a long time, other than pros with lots of money, 99% of photography was done with 35mm, so it was a 'standard' of sorts. When the crop-format digital cameras came in, it was logical to relate the focal length (which 99% of the people in the world think of as magnification!) to the 35mm. Given the proliferation of different sensor sizes now, though, is that still the case?

As far as the magnification vs angle of view goes, it is really a semantic issue. The *effect* of the crop factor is to magnify the image a certain percentage. Only people like us would know the difference, and I hazard to guess, care! I have even seen it referred to as a "zoom factor" - although probably not here! :-D

Samuraiz Loc: Central Florida

It's really a 50mm.

dgkli

I'm relatively new to this forum, but it's amazing to me how many long threads there are on this subject, and how much confusion there is.

As many people have pointed out, the 35mm or FF "equivalent" is simply a reference point used because prior to the advent of digital photography, the majority of consumer-level photographers were 35mm photographers. I know that to me, when someone tells me the "35mm" equivalent of a lens, it's the easiest way for me to imagine how the image will be framed.

If you were never a film photographer, it's probably a useless reference.

More confusing to me: the reference has only limited utility (i.e. angle of view.) When you start discussing lens speed and dof, the equivalency does not hold.

So, I've just started with M4/3. I notice Olympus lenses indicate the 35mm equivalent focal length on the packaging. But lens speed as measured by f-stop is a ratio of focal length to lens diameter. So when you get into "equivalents" you are distorting the meaning of the ratio. An M4/3 25 mm f1.4 lens is NOT the equivalent of a FF 50mm 1.4; it's the equivalent of a 50mm f2.8 in terms of angle of view, speed, and depth of field (I think?) So you need to apply the factor to both the focal length and the f stop if you want to "picture" the equivalence.

I think the camera marketers are somewhat at fault here. They would be perfectly happy for you to think their compact camera 8-35 f2.8 is equivalent to a 28-120 f2.8 FF, which it certainly is not. (I mean really: just look how little it is. It may be technology, but it's not magic!)

It might be best if all of us try not to think in terms of the FF equivalent. How many of you can quickly make the translation of focal length and lens speed for compact cameras? One-inch sensors? 1/1.7, 1/2.3, whatever sensor sizes are out there?

dgkli

Right. What I said!

warrior Loc: Paso Robles CA

Benny Hill says assume is a bad word ass-u-me :D :D :D

Texas_Greek Loc: Austin, TX

Canon factor is 1.6.

rmalarz Loc: Tempe, Arizona

Any focal length lens is just that, whatever the focal length is. A 50mm is always a 50mm. Using a different size sensor does not mystically change the focal length of the lens. What it does is use a different portion of the image the lens is projecting on the light sensitive material. A crop sensor, as an example, may show you the portion of the image that a longer focal length lens would project on the full size sensor, but as for the lens, it's still a 50mm, in our example.
--Bob

Bloke Loc: Waynesboro, Pennsylvania

I'm sorry, but so many people are missing the point I was asking. I know all kinds of things will be different, but I am talking about magnification - or should I say *apparent magnification*!

Let me ask it another way... I like to take wildlife photos. The SX50 has a lens which can really reach out and *grab* something. Now, if I want to buy a bigger lens for my T4i, say, a 400mm. If I had a choice between 2 lenses, one of which is built for crop-factor bodies only, and one which would also work with my metaphorical *next* camera body, would those lenses both give the same *apparent* magnification, or *reach* when stuck on my camera?

I *know* they are both 400mm, but that is just a label. Ever since they started using different crop sensors, the label is really meaningless. What I, representing Joe Photo out there is interested in, is how close can these lenses get me to the subject - you know, the charging grizzly!

CurreyPhoto Loc: Reddick, Florida

The answer is, "yes".

royden Loc: Decatur, GA

Hi Bloke, May I suggest that you take a photo with your EF at 200MM, then take the same shot with the EFS at 200. Use a tripod, if you have one. See what you get. I would try that on my Pentax but every Pentax lens fit my camera. All my 200s act the same way. BTW EF if for full frame

traveler90712 Loc: Lake Worth, Fl.

Bloke, why don't you see for yourself. Go here.

http://static.nikonusa.com/Lens-Simulator/simulator.htm

sshinn1 Loc: Phoenix

Great explanation, thank you! I firmly grasp the focal length/angle of view deal, but never understood why a FF with the same focal length/f stop gave a shallower DOF than a crop sensor, this now makes perfect sense
:thumbup:

Pentaxguy Loc: Western Massachusetts

I use Pentax cameras, which have a 1.5x factor. My 50-135mm f2.8 lens is the equivalent of the full frame 70-200mm lenses. So the answer is, for APS-C cameras like Pentax and Nikon that have that multiplication factor, what is labeled a 50mm lens is the equivalent of 75mm. Used on a full frame film camera, that same lens is 50mm. By the way, the factor on the Canon APS-C cameras is 1.6x.

Bloke Loc: Waynesboro, Pennsylvania

Thanks for the link. What that simulator shows, is that, on a DX (I'm guessing crop?) camera, the 2 lenses would give the same *apparent* magnification. On an FX (full frame?) camera, the lenses would give very different views.

That is interesting.

Thanks to everyone who jumped in on this one!

Kingmapix Loc: Mesa, Arizona

Every lens you buy has on it a focal length number. This number ( 50mm, 35mm, 200mm) refers to its size while mounted on a full frame body. If you have a C-sized body, you multiply that number by 1.5 (for Nikon body) or 1.6 (for Canon body) to arrive at its actual magnification for C-sized bodies. In other words, a 50mm lens on a C-sized body acts like a 75 - 80mm lens on a Full Frame body.