Cropping to digital zoom presets, keeping the aspect ratio.
“Focal length” | Pixels (ref) | Scale (1-dim) |
---|---|---|
28mm | 8368 x 5584 | 1.00 |
35mm | 6704 x 4472* | 0.80 |
50mm | 4688 x 3128* | 0.56 |
75mm | 3136 x 2096 | 0.37 |
90mm** | 2603 x 1740 | 0.31 |
103mm*** | 2280 x 1522 | 0.27 |
166mm**** | 1408 x 939 | 0.17 |
333mm***** | 704 x 470 | 0.08 |
* Cropping in Photomator and respecting original aspect ratio, the 35mm height is +2px and the 50mm height is -2px vs expected.
** The 90mm is featured on the Q3, not Q2, but I simply did 90mm/28mm ≅ 3.214x for the scale factor, and (1/3.214) * 8368px = 2603px.
*** I'm interested in 2280px width because I'm developing a new website media display standard max width of 1140px, so a 2x pixel density means exporting to 2280px width. I reverse approximated the focal length via (8368 / 2280) * 28mm ≅ 102.8mm.
**** I'm also interested in 1408px width because it's 2x the current website text width of 704px. So text-width photos (again, 2x pixel density) would be exported to 1408px width. Focal length again reverse approximated with (8368 / 1408) * 28mm ≅ 166.4mm.
***** Same story for 704px, just a perverse experiment.
I don’t get these crops automatically in Apple Photos or Photomator even when I take a photo with those crop lines on,01 so there isn’t any real reason to abide by these. These just seemed like convenient settings to try.
Question: If the full photo is a 28mm focal length, why do the specs call it a “Digital 35 mm compact camera, fixed focal length?” Is this a convention, or about the sensor size?
Cropping Limits
I am curious about how focus interacts with crop in shallow-DOF photos. Here are a variety of crops shown on a photo:
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Here are each of those crops displayed at text-width.02
28mm (orig) [f1.7]
"35mm" [f1.7]
"50mm" [f1.7]
"75mm" [f1.7]
"90mm" [f1.7]
"166mm" [f1.7]
I am shocked to see that, at this small of a width, the “90mm” crop is totally usable.
Out of sheer curiosity, I cropped down to 1408px, the equivalent to an eye-watering 166mm zoom, and… it looks excellent. This is totally surprising and delightful. I assumed that the raw image pixels didn’t correspond to usable pixels, just a somewhat arbitrary binning of sensor data. But it completely works.
And since if something is worth doing, it’s worth overdoing, I went past the 2x pixel density and made a raw 704px width photo, which I guess would be 333mm.
"333mm" [f1.7]
To me, this finally looks blurry. I think this is because it’s now actually stretched on a 2x pixel density screen. To verify, we can display it 1/2 size03 to make it 2x pixel density again.
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"333mm" [f1.7], displayed 1/2 size for 2x pixel density
Doing this, I realized I’m stupid and this is now just exactly a cutout of the “166mm” photo.
My tentative conclusion is that yes, you really can use each pixel that comes out of the camera.
Practical Limits
On the website, I anticipate exporting at two potential widths:
- 2280px (“103mm”) for wide media of max 1140px @ 2x pixel density
- 1408px (“166mm”) for a text-width media of max 704px @ 2x pixel density
This means, when cropping, those are my realistic boundaries.04
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Here’s what each of these crops look like at their intended display size.
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Crop of 2280px ("103mm"), displayed at max 1140px [f1.7]
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Crop of 1408px ("166mm"), displayed at max 704px [f1.7]
On a big enough screen, the bottom image should just look like a cutout of the top. I.e., they should be at the same scale.
This is, again, delightful because there’s so much room to crop.
Footnotes
I think Lightroom might do it, but I haven’t been willing to take that plunge yet. ↩︎
All crops are exported to 1408px width and displayed at maximum of 704px to allow a 2x pixel density. ↩︎
Sizes are confusing. This cuts each of the width and height in half, so it feels like “half size,” though the area gets cut by 1/4. ↩︎
There are also cover photos, which will probably be bigger. ↩︎