[lguckert79]

so the sensor is smaller than a 35mm negitive so a smaller apature like f:2.4 would be like using an f:1.6 apature with a 35mm negative with the crop factor of 1.5 now is this true or not ??

[rhodopsin]

I think you may be referring to the Zeiss pdf document 'Depth of Field and Bokeh' http://www.zeiss.com/C12567A8003B8B6F/EmbedTitelIntern/CLN_35_Bokeh_EN/$File/CLN35_Bokeh_en.pdf in particular the table on page 10 showing equivalent f-numbers for different sensor formats?

A practical use of that information is determining how to produce identical 8x12 prints, with identical framing and depth of field, from a 35mm camera and APS-C camera using the same lens.

There are two factors. The first is, the distance from subject is greater with APS-C, resulting in DOF increase on the print compared to 35mm. The second is, the APS-C image must be enlarged 1.5 times more than 35mm image, resulting in DOF decrease on the print compared to 35mm. The increase from the first factor is greater than the decrease from the second, so for identical DOF, the lens on APS-C needs to be opened up from f/# used on 35mm -- check a DOF calculator.

[lguckert79]

no that is not what i was going for i want to know if the sensor has a crop factor for the lens you use would the apture have one to like i said useing a f2.4 on a sensor would be the = to useing a 1.6 on film with the amount of light that hits the sensor

[rhodopsin]

Oops!

The f/# is a measure of how much light shines on each unit of area -- the size of film or sensor don't matter. The sensor and film are different sizes but the amount of light shining on each unit of area is the same. For example you could expose a piece of 8x10 film and then a piece of 35mm film in the same camera, same lens, same f/#, same shutter speed, and both pieces of film will be exposed the same.

Wikipedia pages on aperture and exposure may help.

[lguckert79]

cool thank you

[RioRico]

Forget you ever heard of crap factor. It is an obscenity. It is only meaningful to longtime 35mm full-frame photographers who are transitioning to half-frame or APS-C (same thing) and want to compare the angle/field of view (AOV, FOV) of a certain focal length on different sized frames. Otherwise it is a sh!t term. It only leads to confusion among those not experienced with 35mm.

Back in the day, I used 135/FF, 135/HF (35mm full and half frame), 6x6cm, 6x9cm, and 9x12cm cameras, sometimes on the same day. My colleagues and I never heard of nor thought about crap factors -- we just learned how various lenses performed on various formats. IMHO crap factor is as misleading as the "35mm equivalencies" printed on P&S digicams. They are NOT equivalent. Equating different systems is bogus. Just learn how each system works.

[/rant]

[Just1MoreDave]

One day, Pentax may ruin everything by making a K-mount camera with a sensor that's not APC-C sized. Until then, enjoy the freedom. Let go of equivalencies!

Even when I remember all of the conversion formulae and theory correctly, I can't say it ever helped in taking a better photo. Look through the viewfinder. The image will look pretty much like that. That's all you need.

[Gashog]

Dam! All I can add is; the difference between full frame and APC-S is that a normal lens is 50mm for one and 35mm for the other.

[RioRico]

Dam! All I can add is; the difference between full frame and APC-S is that a normal lens is 50mm for one and 35mm for the other.

Those would be long normals. Since 'normal' focal length usually means the diagonal of the frame, then 43mm and 30mm are the actual 'normals'. I'll skip the long rant on normality in 35mm photography. It's been done.

[ Why Don't You And Me Get Normal For A Change? ]

[Gashog]

Figure of speech. And thank you.

[Pablom]

crap factor FTW