dala

Lives in Sweden Sweden
Joined on Aug 12, 2008

Comments

Total: 21, showing: 1 – 20
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Wow, super informative post. I shall be honest, I didn’t really appreciate the grass-field test the first time I read about it, but this time it sank in. I’m now a fan of curved lenses and testing in 3D.

Comment about testing for tilted field, I suppose aligning the camera parallel to the test card must be of utter importance. Roger, how does one do that correctly?

Link | Posted on Dec 25, 2020 at 06:33 UTC as 57th comment | 1 reply

I haven't checked the numbers, but most likely, the largest effect is that a larger sensor requires a larger aperture (in millimeters) lens to give the same equivalent focal length. And it is the amount of photons coming in through the lens that _actually_ matters. The efficiency of the pixels in BSI sensors is so close to 100% these days, so the pixel size is secondary.

Link | Posted on Nov 20, 2020 at 12:54 UTC as 31st comment | 1 reply

Amen

Link | Posted on Oct 25, 2020 at 19:49 UTC as 43rd comment
In reply to:

paulsch: I am mildly annoyed by the “52 mm focal length” paired with “f/2.0 aperture” marketing nonsense. In their presentation Apple even left out the word “equivalent” which makes their statements outright falsehoods.

But apart from that the new iPhones look very interesting and I am eager to see the results of their revamped computational photography.

Hi Tom, I would attribute this to the computational photography in smart phones. It is amazing what it can accomplish with very little light. In weak light conditions, these cameras take multiple exposures and blend them, making it the equivalent of very long exposure times. On the other hand, if you look closely on these pictures, they lack sharpness and gradation in the tones due to very heavy-handed do-noising.

Regarding the comment about the eyepiece of telescopes, in the end a picture is a picture regardless of sensor size and most of the time you view them at approximately the same size and distance. If you need to make very large prints that you inspect closely, you will need more light from a larger aperture to fight poisson noise and overcome diffraction.

Link | Posted on Oct 17, 2020 at 07:06 UTC
In reply to:

paulsch: I am mildly annoyed by the “52 mm focal length” paired with “f/2.0 aperture” marketing nonsense. In their presentation Apple even left out the word “equivalent” which makes their statements outright falsehoods.

But apart from that the new iPhones look very interesting and I am eager to see the results of their revamped computational photography.

It is the amount if light that enters the lens (i.e. the aperture size) that determines the character of the image, e.g. the depth of field, the amount of noise due to the randomness of photons, so called poisson noise (not electronic noise which is something different) and the diffraction limited resolution (i.e. how sharp the lens can be).

The lens will, like you wrote, project this light onto the sensor plane. The sensor itself is these days very efficient and most of the photons are detected. (This is especially true for BSI chips.) So the size of the sensor, the size of the pixels or the number of pixels doesn’t really matter. Only the amount of light coming in to the lens.

This is why I think that the aperture size in e.g. millimeter is the relevant specification. I can add that for this reason, astronomers specify the diameter of the main reflector/refractive element as one of the main specifications of a telescope.

Link | Posted on Oct 15, 2020 at 17:09 UTC
In reply to:

paulsch: I am mildly annoyed by the “52 mm focal length” paired with “f/2.0 aperture” marketing nonsense. In their presentation Apple even left out the word “equivalent” which makes their statements outright falsehoods.

But apart from that the new iPhones look very interesting and I am eager to see the results of their revamped computational photography.

@paulsch The theory is right, but in the last paragraph you make the incorrect conclusion. It is the light projected from a given subject that matters, not the light per unit area of the detector. This is the true concept of equivalence.

Link | Posted on Oct 15, 2020 at 06:43 UTC
In reply to:

paulsch: I am mildly annoyed by the “52 mm focal length” paired with “f/2.0 aperture” marketing nonsense. In their presentation Apple even left out the word “equivalent” which makes their statements outright falsehoods.

But apart from that the new iPhones look very interesting and I am eager to see the results of their revamped computational photography.

The f/2 nomenclature referrers to the relative size of the aperture diameter relative to the focal length. It makes no sense to give one number i “equivalent”” units and not the other.

The f/2 is useful for exposure calculations using film. In digital photography, the only thing that matters is the size of the hole that lets in light (larger is better). Aperture should be stated in millimeters!

Link | Posted on Oct 14, 2020 at 00:06 UTC
In reply to:

Peter Del: If the dark scene requires 1.2, then use Olympus, as it's only 410g, rather than 1090g (smiley face)

The aperture diameter of the Olympus is 25/1.2 = 20.8 mm and 50/1.2 = 41.7 mm for the Nikon. That gives an area of 340.9 vs 1363.5 mm2. So, the light gathering capability is 4 times more for the Nikon...

I think aperture should always be written in millimeters, since that is what truly decides how bright a lens is. (No one calculates exposure time these days, so 1/f doesn't matter.)

Link | Posted on Sep 16, 2020 at 09:17 UTC
On article Hands-on with Olympus' tiny 12-45mm F4 Pro lens (198 comments in total)
In reply to:

dala: Equivalent to 24-80 mm and aperture f/8.

Its so small, because it has so small aperture.

Link | Posted on Feb 19, 2020 at 13:32 UTC
On article Hands-on with Olympus' tiny 12-45mm F4 Pro lens (198 comments in total)
In reply to:

dala: Equivalent to 24-80 mm and aperture f/8.

Sorry 24-90 mm

Link | Posted on Feb 18, 2020 at 07:25 UTC
On article Hands-on with Olympus' tiny 12-45mm F4 Pro lens (198 comments in total)

Equivalent to 24-80 mm and aperture f/8.

Link | Posted on Feb 18, 2020 at 07:25 UTC as 6th comment | 7 replies

It’s amazing how they can produce these precision tools that we use at a cost that is not astronomical!

Link | Posted on Oct 1, 2019 at 18:38 UTC as 36th comment

Nice voting interface. How about a switch to sort the results based on popularity?

Link | Posted on Jul 25, 2018 at 15:48 UTC as 318th comment

This will soon be like the razor blade arms race with Gillette having a 7 blade razor.

http://www.telegraph.co.uk/men/fashion-and-style/11921133/Introducing-the-seven-blade-razor-because-five-just-wasnt-enough.html

Link | Posted on Feb 7, 2018 at 19:14 UTC as 3rd comment
On article A fully loaded iMac Pro will cost you $13,200 (564 comments in total)
In reply to:

Stanchung: Apple will need to come up with a matching monitor so that one can work with multiple screens and not cause some OCD reaction.

Just buy two...

Link | Posted on Dec 15, 2017 at 02:10 UTC
In reply to:

dala: "The 24-72mm F2.8-5.6 sacrifices brightness and zoom range for size, but covers a useful range for everyday photography."

This is super confusing. Focal length given as full-frame equivalents but not the aperture. The optics is actually 15-45mm F2.8-5.6, which with an APS-C is equivalent to a super slow lens of 24-72mm F4.2-8.4.

Journalists (and manufacturers) should always specify when they use FF equivalent numbers. Here he did not specify AND he mixed the two ways.

Link | Posted on Oct 27, 2017 at 06:27 UTC

"The 24-72mm F2.8-5.6 sacrifices brightness and zoom range for size, but covers a useful range for everyday photography."

This is super confusing. Focal length given as full-frame equivalents but not the aperture. The optics is actually 15-45mm F2.8-5.6, which with an APS-C is equivalent to a super slow lens of 24-72mm F4.2-8.4.

Link | Posted on Oct 27, 2017 at 02:39 UTC as 39th comment | 8 replies

So this is an APS-C equivalent of a full-frame 24mm f/2 lens.

(I'd say, with such a big lens you get diminishing return of going with a crop sensor system.)

Link | Posted on Oct 25, 2017 at 06:13 UTC as 17th comment | 1 reply

This lens was talked about recently here:
https://outfor30.com/2017/08/13/a-forgotten-solution/

Link | Posted on Sep 27, 2017 at 13:35 UTC as 19th comment | 1 reply

The focus is on the photographers in the foreground. I'd prefer to have it on the main subject.

Link | Posted on Jun 11, 2017 at 04:28 UTC as 4th comment | 1 reply
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