"Crop-ability" of images?

Started 3 months ago | Discussions thread
bobn2
bobn2 Forum Pro • Posts: 69,811
Re: "Crop-ability" of images?

Donald B wrote:

bobn2 wrote:

Donald B wrote:

Wu Jiaqiu wrote:

Donald B wrote:

Wu Jiaqiu wrote:

john isaacs wrote:

Wu Jiaqiu wrote:

Donald B wrote:

bobn2 wrote:

Donald B wrote:

bobn2 wrote:

Muster Mark wrote:

bobn2 wrote:

dperez wrote:

More photographers who’s judgement I respect are talking about moving to Olympus. A question came up the other day and I’m trying to figure out the answer.

Nikon D850, 600mm f/4 versus M1X, 300mm f/4.

As I understand it - the lenses are the same equivalent - 600mm. The Nikon shoots at f/8 and ISO 3200 and 1/500. The M1X shoots at f/4 so the DOF is the same, and ISO 800 and 1/500, so the exposure is the same, right?

Wrong! Somewhere along the way you've picked up a wrong idea of what 'exposure' means. It does not mean how light or dark the image is. It means what is the light energy density at the sensor. It is determined by shutter speed, f-number and scene luminance. In your example, since the shutter speed and scene luminance are the same, but the f-number is two stops higher on the Nikon, it will have two stops less exposure. But it will make up for it by having four times the sensor area.

I think he was saying he puts the Nikon at f8 and gets the same results as the Oly at F4. This is correct. He has the Nikon shooting at ISO 3200 and the oly at ISO 800. I don't think your criticism of his understanding is warranted.

I didn't criticise his understanding except for the meaning of 'exposure', which he got wrong. This misunderstanding is unfortunately common. As you say, if he was saying that he gets the same 'results' or lightness, then yes, he's right.

I like this quote "The “Exposure Triangle,” as it is often referred to, is a handy way of interpreting the major components involved in the process of capturing an image.

Yes, I think that the 'triangle' is responsible for people thinking wrongly that the components of exposure are aperture, shutter and ISO.

well think of it like this , to expose a viewable image on the camera rear lcd or evf . the camera requires the correct aperture ,shutter speed and iso now try to argue against that

When invented by Bryan Peterson it was the 'Photographic Triangle'. Whatever the name, it's useless.

iso you say....the rabbit hole beckons

Exposure triangle:

https://www.cambridgeincolour.com/tutorials/camera-exposure.htm

Exposure settings:

https://www.adobe.com/creativecloud/photography/hub/guides/camera-exposure-camera-settings.html

Because when people think of "exposure", they think of the image.

ISO does not change the sensor's sensitivity to light though as per the adobe article, it's wrong

a light meter requires 3 inputs from the user for it to work.

There are lots of kinds of light meter, but I suspect you're talking about one particular type, an 'exposure meter'. Even then, it's not the case. Over the history of photography, exposure meters have come in many shapes and forms. To calculate exposure you need the scene luminance and the EV (combination of shutter speed and f-number). Some meters give you a direct reading of scene luminance and then provide tables to calculate exposure, given different EV values. However, mostly photographers have not been so interested in what is the exposure, they want to match the target exposure specified by the ISO (or before that the ASA or DIN). For hand held meters, you's generally set the target exposure, by means of setting the ISO, and the meter would tell you the EV setting to use, or it would separate it out into f-number and shutter speed. You set one, and it tells you the other. For coupled meters the norm was to display the difference from the target exposure with the selected f-number and shutter speed.

Mostly people who make this mistake of what exposure is have never used a separate exposure meter or if they have, haven't understood what they are doing with it.

Don

does that change your sensor's sensitivity to light?

A gain control controls the sensors sensitivity’s, which I presume is the iso control can’t image its further down the track. Same as gain control on a radio receiver.

Din

I thought my typing was bad, but I usually get my own name right.

Anyhow, the gain control on a radio receiver only affects its sensitivity for an AM radio using a diode detector. The amplitude of the carrier needs to be larger than the diode's forward voltage for the signal to be detected, this 'sensitivity', in the sense of what is the smallest signal that can be detected, can be increased by putting gain in front of the detector stage.

But what if you added a multi element yagi with a 6db gain, if a strong station was close the gain control would then need to decrease the signal, wouldnt that be the same as a bright lens and sunny day ?

You'd need an attenuator, not a gain control.

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