Xpatch Loc: New York, Antigua, GT.

I recenly read that The 56mm F1.2 fuji Lens performs (With a 1.5 crop factor) like a 84 mm F1.8 Lens wide OPEN. I knew about ThenFocal length adjustment But never knew the aperture needed to be adjusted also. Îs It Simply math or am i missing something? Any illumination would be appreciated. Does this mean that All the Fuji Lens actualy have a higher f stop than the Lens says?

davidrb Loc: Half way there on the 45th Parallel

You read this where? You offer nothing by using the "I recently read" excuse for a reference. What publication and which author does this reference cite?

amehta Loc: Boston

It is simply math. The idea of "35mm equivalent focal length" has been around for a while. Now there is the idea of "35mm equivalent ISO and f-stop", to allow for similar comparisons.

You have a 56mm f/1.2 lens, nothing more, nothing less. Everything else being mentioned is to compare between different sensor sizes.

Xpatch Loc: New York, Antigua, GT.

Thank You. Thats what i thought.

Xpatch Loc: New York, Antigua, GT.

Davidrd. Tone It down. THE source isnt as important as the Question. In Point of fact. THE INFO came rrom this website- topic board- Hencen i thougt It WAS superflouos to Cite sources, But for THE literelal minded i shouldhave stated that in My Question. Sorty you sidetracked and couldntb address My Question, which is anwered now anyway.

Armadillo Loc: Ventura, CA

Xpatch,

Amehta provided you with a very good direct answer. To illustrate the differences a bit more, the comparisons you were asking about are for those photographers who recently moved up from 35mm SLR camera bodies to DSLR bodies. The comparison is from a full frame (35mm film frame), or full frame DSLR body, to the newer "Cropped Frame" DSLR bodies. The, so called, Cropped Frame bodies have a smaller physical sized sensor than the full framed bodies, this causes a physical alteration on the image size appearing on the cropped frame sensor.

The comparison is only important where you are able to use a lens designed for 35mm body on a body with a cropped sensor.

Your original question was about Aperture, Aperture values remain the same on any given lens, it will not matter what camera body you attache the lens on. In most modern DSLR camera systems the Aperture is controlled by the lens design. The first consideration is the Objective Lens element (the glass that faces the subject), the next consideration is the remaining glass elements internally in the lens body (perhaps less then .25 f/stop), and the final consideration is the Aperture iris inside the lens to restrict the quantity of photons striking the photo sensitive element in the camera body.

Michael G

Xpatch Loc: New York, Antigua, GT.

Thanks Michael. Makes very Good Sense

Armadillo Loc: Ventura, CA

Richard,

You are very welcome. Anytime, just give a shout out.

Michael G

Morning Star Loc: West coast, North of the 49th N.

My first digital camera's sensor was 8.8 x 6.6 mm, the second one 7.1 x 5.3 mm (lenses not interchangeable) and I'm now on 4/3 and micro 4/3 systems (interchangeable lenses).
I've never worried about the crop factor, focal length or aperture. No, I don't ignore them, I just don't worry about them, especially not about comparing them with other cameras. I use the viewfinder, and occasionally the lcd screen, to compose, check colour, light or darkness, and when I'm happy with what I see in the viewfinder I press the shutter release button.
I believe it has improved my photography to use the capabilities of MY camera, without comparing what it does or doesn't do to other cameras.

rocketride Loc: Upstate NY

Actually, Armadillo, what the f# is describing is the size of the lens' "entrance pupil", which is simply described as the size of the stop as imaged by all of the optics between it and the subject.

Take any zoom lens. Look in through the front with the lens wide open. Zoom it back and forth through its range. Notice how the stop appeared to get larger and smaller? Well, it didn't really. What changed was the relative spacing of the lenses in front of the stop and the resulting magnification(s) at which you were viewing it while zooming.

So, the previous description of what determines the f# is just wrong. It's all of the glass in front of the stop, acting together as a unit (and which may act as a powerful magnifier, as in a long-focus lens; or a powerful demagnifier, as in a retrofocus wide-angle, or anywhere in between) and the size of the physical hole that it's imaging that determines the effective aperture. And the f# is just the ratio between that diameter and the lens' focal length at any given setting.

You are correct about the f# being invariant with sensor size and the same lens. All sensor size affects is how much of the real estate where the lens is trying to focus light is occupied by pixels.

David Morrison

Xpatch,If my understanding is correct,then there actually is an adjustment that needs to be thought about, and that is depth of field.Your F1.2 lens put on a 1.5 crop factor camera , at the same given distance to subject,will give a depth of field of an 84mm F1.8, ( not f1.2).It means your blurred background ( or bokeh) will not be the same.
I'd appreciate it if the hogs giving the excellent previous answers to this topic could correct this if it is not correct?

Xpatch Loc: New York, Antigua, GT.

Good Point

rpavich Loc: West Virginia

Whomever said this just meant that in terms of depth of field, it will perform as if it's slightly stopped down as compared to a full frame of the same lens size. In other words...the depth of field you will get from it will "act" like an f/1.8 and not an f/1.2 lens.

The light gathering ability isn't any different than a f/1.2 lens.

Make sense?

amehta Loc: Boston

The light gathering ability depends on the objective lens, not the f-stop. If we talk about lenses with their true focal lengths, then f/2 is f/2. But if we apply a crop factor to the focal length, then it is incorrect to describe a lens using "effective focal length" and "actual f-stop".

rocketride Loc: Upstate NY

A 50mm f/2 lens is the same lens whether it has a sensor the size of a 35mm frame or one six-tenths that on a side at its focus. The only functional difference is in the angular coverage of the lens with each sensor.