Miamark Loc: Florida

I know that there has been some discussion about this is previous posts but I must admit that I still am confused. I understand that the effective focal length of an APC sensor is multiplied by 1.5 or 1.6 due to the crop factor. In essence, since the sensor is smaller than a full frame camera, it appears as to if the picture is 1.5 times greater. However, it seems to me that a 50 mm lens is still a 50 mm lens but it renders the equivalent of a 75 mm lens in 35 mm format. Where I get confused is the effect on aperture. If I have a 50 mm f2 lens, there seems to be some disagreement or confusion whether the effective aperture is f 2.8 or f 3 or f2, If I take a handheld light meter it does not factor in the effective focal length, particularly if it is an incident reading. I doubt that a handheld reflected light reading with a grey card would require an adjustment as well. I suspect that the meters in the cameras do not adjust for effective aperture but I don’t know. While the effective focal length may play a part in the depth of field, you may have to compensate for that with a change in aperture but that should not change the exposure. Could someone explain this to me why, as Tony Northrop (a respected source) and suggests, that you have to multiply the aperature by the crop factor as well.and end my confusion. Thanks.

Ysarex Loc: St. Louis

A lens set to f/2.8 is f/2.8 on all camera formats relative to exposure. The crop factor application to f/stop is to equalize DOF across the different formats. So if you want to take the same photo with both an APS format camera and a FF camera and have equivalent DOF between them then you use the crop factor on the f/stop. To get equal DOF the APS camera needs a wider aperture all else being equal.

CHG_CANON Loc: the Windy City

This topic hasn't died down from 167 replies over 12 pages, and you're asking again?

https://www.uglyhedgehog.com/t-695357-1.html

If TN's technical expertise made him more than a self-proclaimed expert, why not ask him?

Miamark Loc: Florida

Thank you for your rude and unhelpful reply.

CHG_CANON Loc: the Windy City

You're very welcome!

fetzler Loc: North West PA

Take CHG_Cannon's advice and do some reading. The focal length of you lens and its aperture are physical characteristics of your lens and have NOTHING to do with your camera's sensor size.

IDguy Loc: Idaho

Check out Tony Northrup’s youtube on this. He convinced me.

There is no impact on exposure.

It does affect depth of field.

Just something to consider when buying lenses and choosing settings.

Miamark Loc: Florida

Got it.

RWR Loc: La Mesa, CA

f/2.8 is f/2.8, no matter the image size (sensor or film format.)

one_eyed_pete Loc: Colonie NY

It's not about exposure or light meter readings. In the test shots Tony states he used the exact same camera settings with all three bodies. It's the same light per sensor area. The point of multiplying by crop factor is to compare images from different bodies with the same lens in terms of effective focal length and depth of field/bokeh. He also talks about different noise levels because of the differences in sensor pixel count/size and total light received on the sensor pixels, but that gets more complicated.

ronpier Loc: Poland Ohio

Aperture is aperture and it does not change. Makes life easier. I shoot DX(Nikon)and just need to multiply the 1.5 crop factor for focal length. But Aperture Equivalence is set to the 1.5 crop factor for equal comparisons but aperture remains aperture. i.e. f4.2 on FX(Nikon)would be about 2.8 on DX.(Nikon)

Longshadow Loc: Audubon, PA, United States

Worked for me....

I know, I know, it's much easier for people to keep asking the same question over and over,
and over instead of attempting to do any research.

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

You'll need to define what you consider "effective aperture" to be.

Your analysis of what happens when you use an external meter is 100% correct.

Northrup couldn't be more wrong on this. He is unclear but I do understand where he's going - and his observation has to do with just the depth of field. I discussed in my post on your previous thread - it has nothing to do with light on the sensor, and his convoluted explanation has resulted in a lot of very confused people.

Ignore him and your problems will be solved on this and a lot of other stuff. Better yet - test what he says, and then test what you believe to be true - and that will also solve your problems. Starting another thread to elicit even more discussion is not going to help you.

R.G. Loc: Scotland

Sunny 16 works for crop sensor cameras just the same as it does for FF cameras. In other words as far as exposure is concerned, the f-stop is unaffected by crop factor.

However, as far as depth of field is concerned, f/2.8 on a x1.5 crop factor camera will give roughly the same DOF as f/3.3 on a FF camera, all other things being equal (focal length, distance to focus point). The smaller the sensor, the higher the full frame equivalent f-stop. Very small sensor cameras are usually limited to f/8 because of diffraction, whereas medium and large format cameras will happily use f-stops as high as f/64 and beyond.

PHRubin Loc: Nashville TN USA

If you click "Quote Reply" on the post you are responding to as I did here, we can see which one it is.