# how to compare camera to mobile phone?

Started 2 months ago | Discussions thread
Re: Same settings.....

Tony Beach wrote:

PhotoTeach2 wrote:

Tony Beach wrote:

PhotoTeach2 wrote:

SergeyAU wrote:

How did you work out 2-stops? Mobile was f/1.5 and camera was f/3.5. Do you take higher full stop number (f/2 for f/1.5 and f/4 for f/3.5) and subtract?

The f/stops are f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16. (each is double/half the light)

You forgot f/2.

You are RIGHT ... I did skip f/2

I posted that in BED (@ 3am), and skip'd f/2. But I did include it in an earlier post ... https://www.dpreview.com/forums/post/62676909 ... so I do "know" f/2.

So f/1.5 is close to f/1.4 ... and f/3.5 is closest to f/4.

F/1.4 to f/2 is "half" the light, (-1-stop).

No, f/1.4 is twice as much light as f/2

No ... moving from f/1.4 "to" f/2 is half.

So f/1.4 is twice as much as f/2.

BUT ... he is MOVING FROM f/1.4 "to" f/2, (and then f/2.8 and then f/4)

which is twice as much light as f/2.8 which is twice as much light as f/4, so that's eight times more light.

Moving FROM f/1.4 "to" f/2, then "to" f/2.8, and then "to" f/4 -- is 1/8th light, (and 3-stops).

However, because both numbers are fudged the actual difference works out to 2.44 stops.

Yes

Which also means he did NEED that extra ISO boost.

Thus even LESS DESCREPANCY than our original calculation.

The result was less than 1-stop discrepancy, which can easily be within margin-of-error considering it was indeed a phone w/ probably less-accurate ISO calibration, (compared to "real" camera where ISO calibration would be more accurate).

I'm sure you meant ISO "calibration," which is a misnomer as ISO is whatever the camera company says it is and does not reflect a standard of "accuracy."

Well, no ... there is a "standard" ... and HE just PROVED it was closer than we had first assumed.

And here you mention "less than 1-stop discrepancy".

The additional doubling of ISO (1200 to 2400) would normally be another stop, (causing that image to be "1" stop lighter/brighter)

So since his (available "M") f/stop was MORE than "2" stops, and he could ONLY GAIN "2" stops w/ his LONGER SHUTTER-SPEEDS (from 1/4-second "to" 1/2s, "to" 1-second), he NEEDED that extra (1-stop from 1200 "to" 2400), ISO (lightness) boost.

You mean that 2 images LOOK similar to each other to disregard the differences due to ISO calibration?

Yes, I would not trust the accuracy of a phones ISO, (or f/stop-SS), "calibration", so ONLY a 1-stop discrepancy is easily possible within margin-of-error(s).

Ugh -- see above.

Yes ... even less descrepancy

You need to understand what ISO represents, and then you will understand it is not subject to "calibration."

It is a preset "factory" calibration to keep ALL CAMERAS (exposure/lightness) CONSISTENT.

Same with hand-held Light-Meters .... all (factory) set to a ISO "standard".

Just making sure that I understand

Do you understand that even with a Crop-Factor difference of 4.5, (between cell-phone and "M"), the EXPOSURE-SETTINGS did NOT CHANGE, (more than margin-of-error) ???

But you do indeed have a (4.5 stop) longer/deeper DOF and higher-noise w/ phone to "M". (4.5 stop shorter/shallower DOF and lower-noise w/ "M")

And of course there is the 6.1X CF to (FF) equivalent FOCAL-LENGTH.

So I repeat that "equivalence" is over-blown when they imply you cant shoot a smaller-sensor in lower-light.

You just PROVED the cell-phone does it W/ SAME EXPOSURE SETTINGS, (instead of 4.5 stops they want you to think).

NOW YOU ARE GETTING ABSURD ....

Look ... you were RIGHT about me "missing" f/2, (because I wrote it in BED @3am --- I think I correctly included it in an earlier post so I DO KNOW about "f/2") --

But NOW you are CONFUSING a beginner again after HE JUST PROVED YOUR WRONG about everything below.

He "MATCHED" the same "lightness" w/ SAME-OFFSETTING exposure-settings.

There are many ways to match brightness.

He matched it w/ "EQUALLY" offsetting "exposure" f/stops & SS, (& ISO-lightness), settings. They were "equal-offsetting" ... not 4.5-stops different which the "equivalency" gurus maintain it is.

That is exactly the intended way to "offset" f/stops and shutter-speeds for equal/same exposures, (when you want/need to prioritize either aperture or shutter-speeds).

It is exactly the REASON for "A" and "S/Tv" and "P" auto-modes. They will each provide the exact-SAME "exposure" .... but w/ different (offsetting) A and S/Tv settings.

YES .... the "noise" is 4.5 stops higher on cell-phone and DOF is 4.5 stops shorter/shallower on "M".

DOF and image quality are inextricably related.

Absolutely NOT ... in the sense that BOTH longer/deeper and short/shallow DOF have both advantages and disadvantages. (portrait photographers prefer short/shallow to isolate subjects/objects, but most often longer/deeper is better for family/party/travel photography)

I do agree that NOISE and Image-Quality can be inextricably related, (IF the noise is objectionably noticeable).

Take away the noise reduction and start from scratch with those files and see what you have. The smaller sensor is collecting less light overall, and that is reflected by the size of the lens pupils used in the f-number comparison where the pupil of the shorter focal length used on the smaller sensor is actually letting less light through than the smaller f-number but larger pupil on the longer focal length being used on the larger sensor.

But equivalence DOES APPLY to Focal-Length, DOF, and noise-level, (but noise may hot-water if below noticeable or objectionable level).

What I find objectionable about the images shown was the level of noise reduction applied, which wiped out resolution. What I find objectionable about your "teaching" here is that you hint at the relationship between equivalence and image quality and then dismiss it as unimportant. The reason equivalence IS NOT overblown is that it gives us a tool that shows that one can indeed match the output from a smaller sensor to a larger one if you understand that the actual pupil size of the lens being used has to be the same on both formats and that you can't match the results if you only match two of the three variables (FOV, shutter speed, and aperture size) that constitute equivalence.

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