Real Focal Length (Page 2): Incorrect. The only difference between lenses made for a crop sensor and those made for a full frame sensor is the image circle. The focal length of a 50 mm...

mwsilvers Loc: Central New Jersey

agillot wrote:

if the lens is made for a crop sensor camera , it will be right .if for a full size sensor it will not , or older film era lenses are full size .i use them on a crop sensor camera .

Incorrect. The only difference between lenses made for a crop sensor and those made for a full frame sensor is the image circle. The focal length of a 50 mm lens made for an APS-C crop camera, and the focal length of a 50 mm lens designed for a full frame sensor, are identical. The only difference is the angle of view of the resulting image on the crop frame camera which is a result of the smaller sensor. Crop lenses have a smaller image circle designed for the smaller crop sensors

GoofyNewfie Loc: Kansas City

rehess wrote:

My first two 35mm cameras, both range-finder types, were constructed with 45mm lenses.

Yup, me too.
Mine was the Yashica Minister D.
What did you have?

rehess Loc: South Bend, Indiana, USA

GoofyNewfie wrote:

Yup, me too.
Mine was the Yashica Minister D.
What did you have?

First one was Yashica Minster III.

Following your link I was led to a "way back" article about taking a Minister III apart, because of a jammed shutter.
https://web.archive.org/web/20180517200504/http://www.kyphoto.com/classics/yashicaminister.html
Mine jammed about once a year - after four years of that, I gave up and purchased the second one,
a Canon QL-19.

I used that about six years, and then completely submerged it while on a walk with my then-fiance. The repair guy wanted lots of money to restore it, so I purchased my first DSLR, a Pentax ME/SE for our honeymoon. We have been married just over forty years now.

rwilson1942 Loc: Houston, TX

GoofyNewfie wrote:

They do list the correct, actual focal length.
The focal length doesn't change just because it's on a different sized sensor.
Do you really "constantly figure" the FF equivalent while you're shooting?
Just look through the finder and shoot!

Amen!

BebuLamar

Imageandart wrote:

Does anyone know why manufacturers don't use the correct focal length on their lenses for crop sensors? Why do we have to constantly figure that a lens marked 18-200mm is in actuality a 27-300mm lens with a 1.5 crop factor?

The lens that is marked 18-200mm is an 18-200mm. Period. All interchangeable lenses are marked with their real focal length. On some fixed lens cameras (bridge and P&S) they do mark them in 35mm equivalent.

Now may I ask you a question? Why do you have to constantly multiply by the crop factor?
If you do not answer in 2 days I will consider your post as a troll.

GoofyNewfie Loc: Kansas City

rehess wrote:

First one was Yashica Minster III. br br Followin... (show quote)

Congrats on your almost 40 years!
I too have a Canon QL and a Petri7s. I know the Petri has a 45mm lens as well.
Must have either been sticking to the measure of the diagonal of the film to get to a "normal" focal length or it was just easier to make...(shrug)

JDG3

Shot 35 mm film cameras for years with various lens, then switched to digital 10-15 years ago. Since then I have shot digital point and shoot cameras, cell phone cameras and various crop sensor cameras.

I have been taught and understand that the focal length for lens is based on the 35 mm standard used so many years in the film world. It is just a standard used in photography much like other standards of measure. I pick the lens based on the 35 mm STANDARD and could care less what the focal length actually is on my crop sensor. In other words I know from experience what kind of field of view I will get from a 35 mm standard lens when used on a crop sensor. I do not need to do any calculations to know what the actual focal length is. Like others have said here, look through our viewfinder if you do not like what you see, go to another focal length lens or re-position yourself or the subject Not something you have to over think a minor detail.

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

Imageandart wrote:

Does anyone know why manufacturers don't use the correct focal length on their lenses for crop sensors? Why do we have to constantly figure that a lens marked 18-200mm is in actuality a 27-300mm lens with a 1.5 crop factor?

Really? Do you really try to multiply the crop factor when looking through the viewfinder?
I just view through the lens and zoom as I look through to frame what I am shooting. I have shot DX Nikon lenses for years and I have personally not thought about the 1.5 crop factor other then when I buy a lens.

Bill_de Loc: US

Imageandart wrote:

Does anyone know why manufacturers don't use the correct focal length on their lenses for crop sensors? Why do we have to constantly figure that a lens marked 18-200mm is in actuality a 27-300mm lens with a 1.5 crop factor?

The lenses are marked properly and it would be very confusing to put all the different "Equivalent" focal lengths on the lens barrel. In the sample you gave what if the lens is set at 105mm.

If it really mattered the camera manufacturers could display the equivalent focal length in the viewfinder or on the LCD screen. But I don't think enough people need more info in the finder.

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Julian Loc: Sarasota, FL

fetzler wrote:

The focal length of a lens is a physical character... (show quote)

This statement is not correct: the FOV of a lens does not change with with the sensor size. Just like the focal length, the FOV is a characteristic of the lens itself whether its image is projected and focused onto any size surface.

Also, I don't understand your term 'normal focal length' as being determined by the diagonal of the sensor. Please elaborate since you already stated that the focal length does not depend of the film or sensor size. Thank you.

Collhar Loc: New York City.

GoofyNewfie wrote:

They do list the correct, actual focal length.
The focal length doesn't change just because it's on a different sized sensor.
Do you really "constantly figure" the FF equivalent while you're shooting?
Just look through the finder and shoot!

Bill_de Loc: US

Julian wrote:

This statement is not correct: the FOV of a lens does not change with with the sensor size. Just like the focal length, the FOV is a characteristic of the lens itself whether its image is projected and focused onto any size surface.

Also, I don't understand your term 'normal focal length' as being determined by the diagonal of the sensor. Please elaborate since you already stated that the focal length does not depend of the film or sensor size. Thank you.

Not everyone agrees

Smaller sensor size means smaller FOV or a more ¨zoomed in¨ image which causes the photographer to take a step back increasing the distance from the subject.

Why does FOV change for same focal length lens on a different sensor size? This is due to the smaller sensor (smaller than FF) capturing a narrower area of light. Opposite applies to sensors larger than FF. This is better shown with an illustration.

https://www.becomingintermediate.com/travel/2018/2/22/does-crop-factor-effect-focal-length-aperture-and-light-gathering

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Normal Lens

"http://neiloseman.com/the-normal-lens/"

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rehess Loc: South Bend, Indiana, USA

Julian wrote:

This statement is not correct: the FOV of a lens does not change with with the sensor size. Just like the focal length, the FOV is a characteristic of the lens itself whether its image is projected and focused onto any size surface.

This depends on what you mean by the term "FOV". I'm not sure what you mean, but most of us use that term to refer to the width of the image on the sensor .... which most certainly does depend on the sensor {you will even notice appearance of the words "width" and "sensor" in my definition}

Julian wrote:

Also, I don't understand your term 'normal focal length' as being determined by the diagonal of the sensor. Please elaborate since you already stated that the focal length does not depend of the film or sensor size. Thank you.

For some reason, early camera manufacturers decided that a 50mm lens gave the same view when projected on 35mm film that the human eye gives. Today, most people seem to think that you need a wider view, that a lens with a focal length equal to the diagonal of the sensor is more appropriate ..... in the case of 35mm film that would be about 43mm.

rehess Loc: South Bend, Indiana, USA

Imageandart wrote:

Does anyone know why manufacturers don't use the correct focal length on their lenses for crop sensors? Why do we have to constantly figure that a lens marked 18-200mm is in actuality a 27-300mm lens with a 1.5 crop factor?

From what I've seen, some users of prime lenses are the main ones who make that calculation any more - so they know which lens to mount on the camera.

In 1983 I purchased a Pentax Super Program, kitted with a 50mm lens; I used that combination for the next twelve years, the longest I've used any primary camera. In 1995 I was ready to go with AF, and after looking at Pentax, Nikon, and Canon systems, I purchased a Canon EOS Elan kitted with a 28-80mm lens; I used that combination for over eleven years. After a brief fling with a Canon compact digital camera, I purchased a Canon Rebel XT kitted with a 18-55mm lens; the only time I did a comparison calculation was when I purchased the new system and determined it was roughly equivalent to the film system - after that, I just looked through the viewfinder and zoomed to the framing I wanted.

Bugs

Or as the say in the quantum physics world "Shut up and shoot {calculate}!"