iPhone Macro: A Big Day for Small Things • Hacker News Board

Re: iPhone Macro: A Big Day for Small Things

#91

Post by foldr » Thu, Oct 14, 2021, 9:41 PM UTC

defaultname wrote: post #89

foldr wrote: post #80

Earlier quoted context omitted.

Holding constant the target resolution, you need a smaller CoC in proportion to the difference in focal lengths (assuming the viewing angle is also held constant). That removes one of the factors of f. I think it makes sense to assume the same target resolution for the iPhone and the DSLR, even though this isn’t true in practice. The DSLR user is obviously free to downsample their photo to a lower resolution and ther…

"I think it makes sense to assume the same target resolution for the iPhone and the DSLR, even though this isn’t true in practice" It yields a practically perfect comparison of focus. This isn't a trick or handicapping, and the degree of focus/defocus is identical whether that SLR had 10x the resolution. There is utterly nothing arbitrary chosen here, and the amount a tree 10 feet outside the focus is out of focus wi…

My point was that it doesn’t matter what resolution we choose as long as we do the calculations based on the same resolution for both the iPhone and the DSLR (and hence with different values for the CoC in each case, given the different sensor sizes). Thus your value for the iPhone’s CoC derived from its pixel size is irrelevant. We can choose any target resolution we like to make the comparison and get the same result (comparatively speaking).

By resolution here I’m talking about what we could crudely measure in megapixels. Say for example that we have a target resolution of 5MP. We then calculate the corresponding CoC for both cameras based on their respective sensor sizes. You’ll find that the CoC for the iPhone will be smaller in proportion to the difference in focal lengths between the iPhone and DSLR. That cancels out one of the factors of f.

Sudosysgen is saying the same thing, but without going indirectly via the DoF formula that you’ve been using.

Re: iPhone Macro: A Big Day for Small Things

#92

Post by slowhand09 » Thu, Oct 14, 2021, 9:42 PM UTC

jagger27 wrote: post #57

fudged71 wrote: post #52

Surprised to see zero mention of ring lights. A small ring light would be perfect for iPhone macros.

That’s a neat idea for an accessory. I bet you could make a little stick-on or clip-on light pipe that redirects the built-in flash to a tiny ring diffuser around the macro lens.

Google it - theres about a million...

Re: iPhone Macro: A Big Day for Small Things

#93

Post by sudosysgen » Thu, Oct 14, 2021, 9:42 PM UTC

defaultname wrote: post #89

foldr wrote: post #80

Earlier quoted context omitted.

Holding constant the target resolution, you need a smaller CoC in proportion to the difference in focal lengths (assuming the viewing angle is also held constant). That removes one of the factors of f. I think it makes sense to assume the same target resolution for the iPhone and the DSLR, even though this isn’t true in practice. The DSLR user is obviously free to downsample their photo to a lower resolution and ther…

"I think it makes sense to assume the same target resolution for the iPhone and the DSLR, even though this isn’t true in practice" It yields a practically perfect comparison of focus. This isn't a trick or handicapping, and the degree of focus/defocus is identical whether that SLR had 10x the resolution. There is utterly nothing arbitrary chosen here, and the amount a tree 10 feet outside the focus is out of focus wi…

The CoC refers to the circle in the pixel that a point will be focused to. The pixels on an iPhone are much smaller than the pixels on a camera. If you use the same CoC for the iPhone, you are referring to many more pixels than on a DSLR.

Therefore, when you use the same CoC, you are asking the DSLR to be dozens of times closer to perfect focus, in pixel terms, than the iPhone, which is why you are calculating outlandish f stop values.

If instead, you have a target that the object must resolve to a pixel with the same resolution on both, you will arrive to an f stop linearly proportional to the sensor size, instead of proportional to the square of the sensor size.

Re: iPhone Macro: A Big Day for Small Things

#94

Post by defaultname » Thu, Oct 14, 2021, 9:46 PM UTC

sudosysgen wrote: post #93

defaultname wrote: post #89

Earlier quoted context omitted.

"I think it makes sense to assume the same target resolution for the iPhone and the DSLR, even though this isn’t true in practice" It yields a practically perfect comparison of focus. This isn't a trick or handicapping, and the degree of focus/defocus is identical whether that SLR had 10x the resolution. There is utterly nothing arbitrary chosen here, and the amount a tree 10 feet outside the focus is out of focus wi…

The CoC refers to the circle in the pixel that a point will be focused to. The pixels on an iPhone are much smaller than the pixels on a camera. If you use the same CoC for the iPhone, you are referring to many more pixels than on a DSLR. Therefore, when you use the same CoC, you are asking the DSLR to be dozens of times closer to perfect focus, in pixel terms, than the iPhone, which is why you are calculating outlan…

I clearly used completely different CoCs, factoring in the different sensor sizes.

At this point I feel like you are just posting things hoping some future visitor will think that your commitment must demonstrate that you are right. I guess.

Re: iPhone Macro: A Big Day for Small Things

#95

Post by sudosysgen » Thu, Oct 14, 2021, 9:46 PM UTC

defaultname wrote: post #79

throwanem wrote: post #72

Earlier quoted context omitted.

If you know a way to focus-stack a live and highly active subject, I'm all ears. But where's your work? To judge by your response here, you must certainly be much better at this than I am, and I'd like the opportunity to derive some small benefit from the extensive experience that gives you so confidently to take such a superior tone.

"If you know a way to focus-stack a live and highly active subject, I'm all ears." You don't, which is why higher depth of field is the golden standard. See: The entirety of this discussion. "so confidently to take such a superior tone" To be clear, you dismissed my post by claiming that it's a "fixed" issue, then posting proof that doesn't show it to fixed. I don't believe I'm the one who attempted a superior tone.…

Small focal length cameras only have an advantage when the sensor size is the same. If you are decreasing the sensor size and keeping the resolution constant, the "small focal length" camera has zero advantage. There is no difference between a 4mm lens at f/2 that is a, say, 30mm FF equivalent and a 30mm full-frame lens at f/15. Precisely zero difference.

Re: iPhone Macro: A Big Day for Small Things

#96

Post by sudosysgen » Thu, Oct 14, 2021, 9:47 PM UTC

defaultname wrote: post #94

sudosysgen wrote: post #93

Earlier quoted context omitted.

The CoC refers to the circle in the pixel that a point will be focused to. The pixels on an iPhone are much smaller than the pixels on a camera. If you use the same CoC for the iPhone, you are referring to many more pixels than on a DSLR. Therefore, when you use the same CoC, you are asking the DSLR to be dozens of times closer to perfect focus, in pixel terms, than the iPhone, which is why you are calculating outlan…

I clearly used completely different CoCs, factoring in the different sensor sizes. At this point I feel like you are just posting things hoping some future visitor will think that your commitment must demonstrate that you are right. I guess.

You clearly did not. If you scaled the CoC exactly with the crop factor, we would find exactly the same numbers.

Re: iPhone Macro: A Big Day for Small Things

#97

Post by defaultname » Thu, Oct 14, 2021, 9:54 PM UTC

sudosysgen wrote: post #90

defaultname wrote: post #86

Earlier quoted context omitted.

"I can't help you" No, you can't, because you are painfully ignorant on this topic. Literally, spend 30 minutes with an iPhone and an SLR and you'd be illuminated. Instead you seriously argue that I need to look at the "physics" (which is farcical when you ignore the most important part of a camera, which is the focusing from the lens to the sensor. Dismissing that betrays a complete misunderstanding of optics). This…

I have a phone with a macro lens. I have a mirrorless camera. As I told you, what matters for bokeh is the distance to the object and the diameter of the aperture. The iPhone needs computational bokeh because the aperture is 2.4mm wide, whereas one of my lenses has a 40mm aperture. That's why my camera produces more bokeh - the aperture has a wider diameter while the distance to the object is the same. That is litera…

You understand that cameras don't use a slit, right? Do you understand the optics in a modern camera?

Further my 70mm lens has a smaller aperture than my 35mm f1.4 lens. Yet it has a much smaller depth of field for a given distance. Weird! Lens makers must not know your remarkable "slit lens" trick.

At this point I'm convinced you are either trolling, or have dug so far into the depths of wrongness that you're dedicated to sticking with it. So good luck with that. I'm out of this conversation.

Re: iPhone Macro: A Big Day for Small Things

#98

Post by CharlesW » Thu, Oct 14, 2021, 9:55 PM UTC

brudgers wrote: post #39

fastaguy88 wrote: post #8

It is may be worth mentioning that it is very difficult to get such amazing pictures without a very stable setup -- both for the subject and for the camera. Even if you have enough light for a high shutter speed, it can be difficult to compose a macro shot if there is any motion at all. And, as was pointed out, lighting/shadows can be tricky when the "camera" lens is just a few inches away.

Yes. “Use a friggin tripod” still applies. So does “bring your own damn light.”

Also, you can avoid touching the iPhone when you shoot by using a timer, a Bluetooth shutter remote, or your Apple Watch (Halide has a watchOS companion app).

Re: iPhone Macro: A Big Day for Small Things

#99

Post by sudosysgen » Thu, Oct 14, 2021, 10:02 PM UTC

defaultname wrote: post #97

sudosysgen wrote: post #90

Earlier quoted context omitted.

I have a phone with a macro lens. I have a mirrorless camera. As I told you, what matters for bokeh is the distance to the object and the diameter of the aperture. The iPhone needs computational bokeh because the aperture is 2.4mm wide, whereas one of my lenses has a 40mm aperture. That's why my camera produces more bokeh - the aperture has a wider diameter while the distance to the object is the same. That is litera…

You understand that cameras don't use a slit, right? Do you understand the optics in a modern camera? Further my 70mm lens has a smaller aperture than my 35mm f1.4 lens. Yet it has a much smaller depth of field for a given distance. Weird! Lens makers must not know your remarkable "slit lens" trick. At this point I'm convinced you are either trolling, or have dug so far into the depths of wrongness that you're dedica…

Revolve the entire setup around the axis perpendicular to the slit and you will have a very accurate representation of how a camera-lens system works.

The ratio between distance and focal length only works if the focal lengths are equivalent across the two cameras. Otherwise it doesn't work. That's to say, a 70mm f/2.8 has the same depth of field as a 35mm 1.4 lens if the second is on a camera with 2x crop factor.

Try it out, crop the image of your 70mm lens at f/2.8 and compare it to the image of your 35mm f/1.4 lens and you will get exactly the same image with the same blur (assuming the lenses are exactly 70mm and 35mm at the focus setting, which is not guaranteed due to focus breathing and manufacturers rounding off their focal lengths)

Re: iPhone Macro: A Big Day for Small Things

#100

Post by defaultname » Thu, Oct 14, 2021, 10:05 PM UTC

foldr wrote: post #91

defaultname wrote: post #89

Earlier quoted context omitted.

"I think it makes sense to assume the same target resolution for the iPhone and the DSLR, even though this isn’t true in practice" It yields a practically perfect comparison of focus. This isn't a trick or handicapping, and the degree of focus/defocus is identical whether that SLR had 10x the resolution. There is utterly nothing arbitrary chosen here, and the amount a tree 10 feet outside the focus is out of focus wi…

My point was that it doesn’t matter what resolution we choose as long as we do the calculations based on the same resolution for both the iPhone and the DSLR (and hence with different values for the CoC in each case, given the different sensor sizes). Thus your value for the iPhone’s CoC derived from its pixel size is irrelevant. We can choose any target resolution we like to make the comparison and get the same resu…

The CoC for the iPhone is smaller than the ASP-C given the smaller sensor. By choosing the same resolution of an ASP-C sensor, we are calculating for a given level of "good enough for that resolution". It is perfectly comparable level of focus. I have no idea why you are so caught up in distractions.

I calculated the hyperfocal length for an iPhone and an equivalent zoom SLR, at the same aperture. These yield effectively identical degrees of focus from 1/2 the HF to infinity. The iPhone is from 3.2ft to infinity, the SLR is from 27 feet to infinity.

Nothing else matters if you can't tell me why that's wrong. Because it isn't wrong. It's absolutely right. The same zoom level and cropping. MASSIVELY larger focus zone.

If we doubled both dimensions of the sensor, thus doubling the CoC, it would halve the HF. If we instead doubled the focal length it QUADRUPLES the HF. The focal length is a squared factor and outweighs any other component. For a reason.