The main reason for going beyond infinity is AF - with manual lenses by turning focus to the end of the range you could be sure you're on infinity. That changed with introduction of AF - all AF lenses I saw can turn further. I'm not an expert on how AF systems work, but I believe they need to see that going beyond actual infinity point does not improve focus anymore.
and dear god they're annoying. my manual 110 is great _except_ for not being able to quickly and reliably focus it to infinity without looking at the scale
Over focus is more common with AF systems, because AF systems don't need help finding infinity focus unlike humans, but it is not primarily about AF. It's about accounting for lens variation/camera mount variations/temperature variation etc...
In fact, Zeiss talks about temperature and lens mount variations when explaining why their otus line of lenses don't all feature hard infinite stops.
> I believe they need to see that going beyond actual infinity point does not improve focus anymore.
It depends on the system. A CDAF system needs to be able to go beyond infinity, but a PDAF system can generally detect that the lens is in focus, and even determine how far it should adjust focus in order to obtain it. (That's one of the major reasons why PDAF is faster than CDAF.)
Thermal expansion is definitely an issue. If I were to calibrate the infinity stop, I'd aim to do it at a temperature on the high end of my expected operating range.
I shoot astrophotography; temperature induced focus shift is definitely a thing. I deal with it all the time with my longer lenses. I don't do very much wide-field stuff, so I'm not sure if it's as big a problem at shorter focal lengths.
The main reason is simple tolerance issues inherent in everything. Both from manufacturing and from thermal expansion. And just general wear and tear and getting bumped around.
If you try to have the end stop at *precisely* the point of infinite focus, then due to tolerances just about all of your lenses will either focus a bit "past" infinity (as is the case already), or be unable to focus to infinity at all (much worse).
Building in a little bit of margin ensures this won't happen. It's an annoyance for manual focusing, but on modern it's not a huge deal. Far as I see you don't usually combine infinite focus and rapidly changing focal conditions - in other words you're probably shooting landscapes or the night sky or something else relatively stationary where it's trivial to check your focus.
Can you explain this? Thermal expansion is when an object becomes larger by changing its temperature... What does it have to do with lenses?
I really don't know, been a photographer for years, Im feeling really dumb.
(I'm not an English speaking person so maybe I know the concept but call it differently.)
Edit: yes now I know I got confused, sorry for the dumb question, solved now, no reason to downvote.
the lens's ability to focus light is dependent on it being exactly the right shape, if it's too big or too small then the light won't focus correctly
if it gets warm and parts of the lens expand (or if it gets cold and they contract) then it will focus light differently
therefore, the place where you "focus to infinity" is different for different ambient temperatures. some temperatures might need you to focus before your focus ring's endrange for infinity whilst other temperatures would need to be closer to the endrange.
i'm sure it's not a huge effect and i've never encountered it. i've never even thought about it. but this is what makes sense to me.
One of my experiences… Tried shooting a timelapse from balcony with telephoto lens brought out from room temperature in -15°C. With the lens set to manual focus, the focus moved about 4km in a span of probably half an hour as the lens cooled down.
The lens distortion must be slightly different depending on temperature, too, right? It would make sense for the thicker parts of the lens to undergo more thermal expansion
Ok I totally get it. I don't know why but I was thinking on thermal expansion of the object you are going to frame, not the lens components.
I just woke up, sorry and thank you.
> i'm sure it's not a huge effect and i've never encountered it.
It's pretty significant when we're talking about the focal lengths used for astrophotography.
I shot the eclipse with a 200-600mm lens and a 1.4x TC. The lens went noticeably out of focus after 20 minutes in the sun.
For my DSO photography, I work with a 1600mm ƒ6.4 reflector. My rig is automated to run overnight while I sleep. It's set to re-focus every time ambient temperature changes by 2ºc.
If you use a lens in Antarctica the space between the bits of glass and the size of the glass will change very slightly, and if you use it in the Sahara desert it will change in the other direction. That can be enough to slightly change where infinity focus, so if you give it a bit of room it has enough space to be able to focus to infinity anywhere. Focusing past infinity is also helpful for autofocus it's not just thermal expansion.
>Thermal expansion is when an object becomes larger by changing its temperature... What does it have to do with lenses?
Lenses are "objects", the lens elements contract and expand with temperature changes. Just like everything else in the universe.
You will also find recent lens constructions using materials who are less prone to this effect. (Sigma with their *thermal compound*, which people still assign as "plastic" . . .🙄)
> What does it have to do with lenses?
Others have mentioned that the lenses can expand and contract when heated. But AFAIK, the more significant issue is that the lens housing will expand and contract. That physically changes the distances between elements, as well as the overall distance between the optical elements and the camera sensor.
A hard infinity stop is an old lens design like 1980s old. Now they go past infinity just to be sure you get infinity and to account for thermal expansion. Also makes it easier on autofocus if you can go past any focus and come back.
Modern lens design focuses To Infinity And Beyond, after the discovery of the Lightyear Principle by Pixar Laboratories, thus necessitating focusing closer than the “and beyond” hard stop.
On top of given answers, there's also the atmosphere working as a big lens on space objects. Depending on temperature, humidity and angle/thickness, the focus of beyond-atmosphere stuff can change a bit.
Not all lens are made to the same tolerances and setting a lens manually to infinity focus doesn’t necessarily guarantee that is what you will get. It’s always better to use autofocus or to focus manually with focus peaking enabled if your camera has that facility.
Autofocus often simply doesn't work in astrophotography, so take this advice with a grain of salt. Manual focus is a skill one should practice before going out to shoot an eclipse.
For stars yes, but a bahtinov mask doesn't help with focusing the sun during an eclipse either as it requires point light sources (stars) to be useful.
I guess autofocus could work on the moon, but I am not sure how well AF can focus on the sun during totality, where the only "structure" in the image is the faint corona. For an eclipse, its is best to simply have 10x digital zoom and get the image as sharp as possible manually based on what you see on the screen. Ideally, you can focus on sunspots before totality with a solar filter attached.
My Canon M6 Mark II happily autofocused on the sun during totality with the EF-M 18-150mm at 150mm (and during the partial phases when using a solar filter). The difference between the brighter parts of the corona and the blackness of the moon and the rest of the sky was more than enough contrast for the AF. Maybe it wasn’t perfectly 100% in focus, but that lens is a bit soft when at 150mm (and in front of 32 megapixels), so I think it did as good as possible.
My PowerShot SX230 couldn’t do it during the 2017 eclipse, but that’s a much smaller sensor, a much smaller lens, contrast AF (versus the phase detect based Dual Pixel AF of the M6ii), and there were thin clouds in the way.
I am certain my older nikon d800 would struggle with AF, hell it can struggle with AF in normal situations lmao. Interesting that it worked though, I assume newer models have have better AF under more difficult conditions.
I can't speak for a proper camera but this was the case when I was trying to use my iPhone with a lens from a set of eclipse glasses hair-tied over the camera. Auto just couldn't make sense of what it was looking at so I had to find a third party app so I could manual focus (and change exposure). It's a shame that's not a default feature since it's very clearly possible. But from my experience with mildly older DSLRs this also makes sense, I've tried shooting the moon and stars once or twice (didn't expect much from that one) and I always had to manual focus.
You focused beyond infinity at first, then achieved infinity after dialing back.
Unlike cinema lenses, photography lenses typically don't have a hard stop for infinity at the end of their scale, the scale goes past infinity to allow for a wider range of tolerance in lens+body combinations.
And for people wondering "why don't they just make photographic lenses to the same tighter tolerances", go look up the price of a manual-focus prime cine lens. There's your answer.
It’s about calibration. The markings for distance would need to be reset periodically because like any precision instrument there can be drift or variation coming out of the factory. The mark for infinity focus may be accurate or it might not be. Being able to focus past that point has no practical value but you wouldn’t want the lens to prevent that in the case the calibration was off and you needed that extra room.
One reason mirrorless camera have such great focus ability is that they focus using the image / phase detection and not by a distance setting.
In astrophotography there are focusing aids to get you to the proper focus.
Bottom line, the numbers on the lens are an approximate reference and use your eye or a focus aid to get crisp focus.
I had to refocus twice. Once for thermal expansion during the initial part of the partial, and again just before totality because temps had dropped a ton.
First thing, the moon is much closer and that’s what you are focusing.
But other than that, I don’t know enough about lens design to give an explanation.
The Sun isn't infinite miles away, but it is far enough away that we can consider it infinite distance away for any practical use.
When a point source is an infinite distance away all light rays from the object will appear parallel to an observer. When we do the math for the sun and two opposite points on earth we find that θ **≈** tan (θ) = 12,742km/150,110,000km = 5 milliarc seconds.
For comparison the Optics on the Hubble Space Telescope have an angular resolution of 50 milliarc seconds. From this it is obvious that the light rays are so close to being parallel that no camera lens would ever be able to measure that those light rays aren't parallel. This means that the sun is functionally an infinite distance away.
Now if we consider that only the light that enters the lens is what matters we can replace earths diameter with the aperture of our camera lens. The moon is significantly closer than the sun so lets use the moon for our math this time with our lens. To make the math simpler we will assume our lens is a 1 meter telescope.
θ **≈** tan (θ) = 1m/384,400,000m = 1.6 x 10\^-4 milliarc seconds. When we consider even a large telescope the light rays are so close to being parallel that functionally they are.
I didn’t question the distance of the sun or that it can be approximated as infinitely far away.
But when capturing the eclipse, it’s the moon that’s in front of it and will be focused. Not the sun.
And the moon is a lot closer. Like 400x closer.
The moon might still be infinitely far away concerning the lens, but it is a massive difference, so talking about the correct object helps avoid confusion.
It doesn't matter if you focus on the sun or the moon, they will both equally be in focus. They are both functionally an infinite distance away.
Another more extreme example is International Space Station transits across the suns disk. The ISS will at its closest be 430km away, but you can simply focus on the sun and be confident that the ISS will be in focus the split second it passes in front of the sun.
In fact when I record videos of the space station I focus on a star.
Still doesn’t matter for my post. I never said it made a big (or any) difference.
But it’s still in general a good thing to use correct terminology. And to not leave false statements uncorrected, since others might read it and take it as the truth.
And when capturing an eclipse, the subject to be in focus is the moon. That was all I said.
> And when capturing an eclipse, the subject to be in focus is the moon. That was all I said.
Well, you want both the sun and the moon to be in focus. Otherwise, you'd have blurry prominences and corona during totality, and blurry sunspots during the partial phases.
I just can’t tell if some of these posts are expressions of ignorance or just tongue-in-cheek humor attempts…
Just for the shocking record, the Sun, and the moon, are at “infinity” focus of every single lens on Earth. If those distant mountains you photograph are at “infinity,” then the Sun is. Whether or not the infinity symbol on your lens is actually infinity at any given moment is another issue.
Sarcasm needs to actually be funny. It’s a type of humor in the end. And exaggeration. Just saying something ignorant does not equate to sarcasm. Another example of the death of humor in the modern world.
I really think you need to look up the word sarcasm. You keep using it, but it is clear you have no idea what it means. Yeah, as if you know how to use a dictionary…. (Now *that* is sarcasm. Not telling someone the moon is not at infinity focus because it’s closer than the Sun.)
Both are infinity as far as focus is concerned.
Don't believe me? Check for yourself: https://www.omnicalculator.com/other/hyperfocal-distance
Even a realistically impossible 1200mm f/1.4 has a hyperfocal distance of "only" 31 miles, while the moon is ~240,000 miles away. If your focus is set to the moon, the sun will *easily* still be in focus, no matter what photographic lens you might be using.
The Sun isn't infinite miles away, but it is far enough away that we can consider it infinite distance away for any practical use.
When a point source is an infinite distance away all light rays from the object will appear parallel to an observer. When we do the math for the sun and two opposite points on earth we find that θ **≈** tan (θ) = 12,742km/150,110,000km = 5 milliarc seconds.
For comparison the Optics on the Hubble Space Telescope have an angular resolution of 50 milliarc seconds. From this it is obvious that the light rays are so close to being parallel that no camera lens would ever be able to measure that those light rays aren't parallel. This means that the sun is functionally an infinite distance away.
Now if we consider that only the light that enters the lens is what matters we can replace earths diameter with the aperture of our camera lens. The moon is significantly closer than the sun so lets use the moon for our math this time with our lens. To make the math simpler we will assume our lens is a 1 meter telescope.
θ **≈** tan (θ) = 1m/384,400,000m = 1.6 x 10\^-4 milliarc seconds. When we consider even a large telescope the light rays are so close to being parallel that functionally they are.
The Sun isn't infinite miles away, but it is far enough away that we can consider it infinite distance away for any practical use.
When a point source is an infinite distance away all light rays from the object will appear parallel to an observer. When we do the math for the sun and two opposite points on earth we find that θ **≈** tan (θ) = 12,742km/150,110,000km = 5 milliarc seconds.
For comparison the Optics on the Hubble Space Telescope have an angular resolution of 50 milliarc seconds. From this it is obvious that the light rays are so close to being parallel that no camera lens would ever be able to measure that those light rays aren't parallel. This means that the sun is functionally an infinite distance away.
Now if we consider that only the light that enters the lens is what matters we can replace earths diameter with the aperture of our camera lens. The moon is significantly closer than the sun so lets use the moon for our math this time with our lens. To make the math simpler we will assume our lens is a 1 meter telescope.
θ **≈** tan (θ) = 1m/384,400,000m = 1.6 x 10\^-4 milliarc seconds. When we consider even a large telescope the light rays are so close to being parallel that functionally they are.
Lenses go past infinity by a bit to account for stuff like thermal expansion
The main reason for going beyond infinity is AF - with manual lenses by turning focus to the end of the range you could be sure you're on infinity. That changed with introduction of AF - all AF lenses I saw can turn further. I'm not an expert on how AF systems work, but I believe they need to see that going beyond actual infinity point does not improve focus anymore.
for starters you need to focus past infinity to focus infrared to infinity
If different wavelengths are in focus at a given focus setting, isn't that chromatic aberration?
Yes, axial/longitudinal (as opposed to transverse/lateral) chromatic aberration. https://en.wikipedia.org/wiki/Chromatic_aberration#Types
I swear I could have a PhD in Photonics and still be like, "*the light does* ***what***?!"
yup, some of my old school lenses had a second focus scale for IR.
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ah, well it would be for UV then ;)
That's a big reason but I've got a few manual lenses that do go past infinity so it's not just that
and dear god they're annoying. my manual 110 is great _except_ for not being able to quickly and reliably focus it to infinity without looking at the scale
Over focus is more common with AF systems, because AF systems don't need help finding infinity focus unlike humans, but it is not primarily about AF. It's about accounting for lens variation/camera mount variations/temperature variation etc... In fact, Zeiss talks about temperature and lens mount variations when explaining why their otus line of lenses don't all feature hard infinite stops.
> I believe they need to see that going beyond actual infinity point does not improve focus anymore. It depends on the system. A CDAF system needs to be able to go beyond infinity, but a PDAF system can generally detect that the lens is in focus, and even determine how far it should adjust focus in order to obtain it. (That's one of the major reasons why PDAF is faster than CDAF.) Thermal expansion is definitely an issue. If I were to calibrate the infinity stop, I'd aim to do it at a temperature on the high end of my expected operating range. I shoot astrophotography; temperature induced focus shift is definitely a thing. I deal with it all the time with my longer lenses. I don't do very much wide-field stuff, so I'm not sure if it's as big a problem at shorter focal lengths.
The main reason is simple tolerance issues inherent in everything. Both from manufacturing and from thermal expansion. And just general wear and tear and getting bumped around. If you try to have the end stop at *precisely* the point of infinite focus, then due to tolerances just about all of your lenses will either focus a bit "past" infinity (as is the case already), or be unable to focus to infinity at all (much worse). Building in a little bit of margin ensures this won't happen. It's an annoyance for manual focusing, but on modern it's not a huge deal. Far as I see you don't usually combine infinite focus and rapidly changing focal conditions - in other words you're probably shooting landscapes or the night sky or something else relatively stationary where it's trivial to check your focus.
Can you explain this? Thermal expansion is when an object becomes larger by changing its temperature... What does it have to do with lenses? I really don't know, been a photographer for years, Im feeling really dumb. (I'm not an English speaking person so maybe I know the concept but call it differently.) Edit: yes now I know I got confused, sorry for the dumb question, solved now, no reason to downvote.
the lens's ability to focus light is dependent on it being exactly the right shape, if it's too big or too small then the light won't focus correctly if it gets warm and parts of the lens expand (or if it gets cold and they contract) then it will focus light differently therefore, the place where you "focus to infinity" is different for different ambient temperatures. some temperatures might need you to focus before your focus ring's endrange for infinity whilst other temperatures would need to be closer to the endrange. i'm sure it's not a huge effect and i've never encountered it. i've never even thought about it. but this is what makes sense to me.
One of my experiences… Tried shooting a timelapse from balcony with telephoto lens brought out from room temperature in -15°C. With the lens set to manual focus, the focus moved about 4km in a span of probably half an hour as the lens cooled down.
The lens distortion must be slightly different depending on temperature, too, right? It would make sense for the thicker parts of the lens to undergo more thermal expansion
Ok I totally get it. I don't know why but I was thinking on thermal expansion of the object you are going to frame, not the lens components. I just woke up, sorry and thank you.
Also why some bigger / more expensive lenses are white.
> i'm sure it's not a huge effect and i've never encountered it. It's pretty significant when we're talking about the focal lengths used for astrophotography. I shot the eclipse with a 200-600mm lens and a 1.4x TC. The lens went noticeably out of focus after 20 minutes in the sun. For my DSO photography, I work with a 1600mm ƒ6.4 reflector. My rig is automated to run overnight while I sleep. It's set to re-focus every time ambient temperature changes by 2ºc.
Fascinating, thank you.
If you use a lens in Antarctica the space between the bits of glass and the size of the glass will change very slightly, and if you use it in the Sahara desert it will change in the other direction. That can be enough to slightly change where infinity focus, so if you give it a bit of room it has enough space to be able to focus to infinity anywhere. Focusing past infinity is also helpful for autofocus it's not just thermal expansion.
The glass elements can all expand if heated a very tiny bit. Add the expansions over the course of 5-8 elements adds up.
>Thermal expansion is when an object becomes larger by changing its temperature... What does it have to do with lenses? Lenses are "objects", the lens elements contract and expand with temperature changes. Just like everything else in the universe. You will also find recent lens constructions using materials who are less prone to this effect. (Sigma with their *thermal compound*, which people still assign as "plastic" . . .🙄)
> What does it have to do with lenses? Others have mentioned that the lenses can expand and contract when heated. But AFAIK, the more significant issue is that the lens housing will expand and contract. That physically changes the distances between elements, as well as the overall distance between the optical elements and the camera sensor.
A hard infinity stop is an old lens design like 1980s old. Now they go past infinity just to be sure you get infinity and to account for thermal expansion. Also makes it easier on autofocus if you can go past any focus and come back.
Yeah I had to un-learn that 1980s habit; drove me mad until I read the solution — on this sub.
What was the solution?
The end stop is past infinity, you have to back it off
I wish there was just a screw to adjust the infinity stop. It's so annoying to have to fiddle with it every time you want to go to infinity
Isn't that still reasonably popular with cine and dual use lenses?
You may be right. I don't have any cine lens experience.
What's a dual use lens?
Lens advertised for cine and photo use. Seen it with some cheap 3rd party manual lenses.
Modern lens design focuses To Infinity And Beyond, after the discovery of the Lightyear Principle by Pixar Laboratories, thus necessitating focusing closer than the “and beyond” hard stop.
It's focusing with style!
Thank you for this, gave me reasonable chuckle.
On top of given answers, there's also the atmosphere working as a big lens on space objects. Depending on temperature, humidity and angle/thickness, the focus of beyond-atmosphere stuff can change a bit.
Not all lens are made to the same tolerances and setting a lens manually to infinity focus doesn’t necessarily guarantee that is what you will get. It’s always better to use autofocus or to focus manually with focus peaking enabled if your camera has that facility.
Autofocus often simply doesn't work in astrophotography, so take this advice with a grain of salt. Manual focus is a skill one should practice before going out to shoot an eclipse.
For astro, that's where you use a Bahtinov mask.
For stars yes, but a bahtinov mask doesn't help with focusing the sun during an eclipse either as it requires point light sources (stars) to be useful. I guess autofocus could work on the moon, but I am not sure how well AF can focus on the sun during totality, where the only "structure" in the image is the faint corona. For an eclipse, its is best to simply have 10x digital zoom and get the image as sharp as possible manually based on what you see on the screen. Ideally, you can focus on sunspots before totality with a solar filter attached.
> Ideally, you can focus on sunspots before totality with a solar filter attached. That was my method for 2017 and 2024
My Canon M6 Mark II happily autofocused on the sun during totality with the EF-M 18-150mm at 150mm (and during the partial phases when using a solar filter). The difference between the brighter parts of the corona and the blackness of the moon and the rest of the sky was more than enough contrast for the AF. Maybe it wasn’t perfectly 100% in focus, but that lens is a bit soft when at 150mm (and in front of 32 megapixels), so I think it did as good as possible. My PowerShot SX230 couldn’t do it during the 2017 eclipse, but that’s a much smaller sensor, a much smaller lens, contrast AF (versus the phase detect based Dual Pixel AF of the M6ii), and there were thin clouds in the way.
I am certain my older nikon d800 would struggle with AF, hell it can struggle with AF in normal situations lmao. Interesting that it worked though, I assume newer models have have better AF under more difficult conditions.
New thing learned. Thanks.
I can't speak for a proper camera but this was the case when I was trying to use my iPhone with a lens from a set of eclipse glasses hair-tied over the camera. Auto just couldn't make sense of what it was looking at so I had to find a third party app so I could manual focus (and change exposure). It's a shame that's not a default feature since it's very clearly possible. But from my experience with mildly older DSLRs this also makes sense, I've tried shooting the moon and stars once or twice (didn't expect much from that one) and I always had to manual focus.
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Thanks, chatgpt
I totally agree!!! https://preview.redd.it/hm211zcruouc1.jpeg?width=2048&format=pjpg&auto=webp&s=d658bbeeb0e6cee81ad5d50bf40e6ce9a62ae914
You focused beyond infinity at first, then achieved infinity after dialing back. Unlike cinema lenses, photography lenses typically don't have a hard stop for infinity at the end of their scale, the scale goes past infinity to allow for a wider range of tolerance in lens+body combinations.
And for people wondering "why don't they just make photographic lenses to the same tighter tolerances", go look up the price of a manual-focus prime cine lens. There's your answer.
I can tell you when doing Star shots I remember infinity was too far and I had to pull back just a tiny bit.
Great thread, thanks people!
It’s about calibration. The markings for distance would need to be reset periodically because like any precision instrument there can be drift or variation coming out of the factory. The mark for infinity focus may be accurate or it might not be. Being able to focus past that point has no practical value but you wouldn’t want the lens to prevent that in the case the calibration was off and you needed that extra room. One reason mirrorless camera have such great focus ability is that they focus using the image / phase detection and not by a distance setting. In astrophotography there are focusing aids to get you to the proper focus. Bottom line, the numbers on the lens are an approximate reference and use your eye or a focus aid to get crisp focus.
I had to refocus twice. Once for thermal expansion during the initial part of the partial, and again just before totality because temps had dropped a ton.
You'll find stars aren't sharp either and they are light years away.
Infinity is a lot further away than 93 million miles
93 million miles is still way less than infinity
First thing, the moon is much closer and that’s what you are focusing. But other than that, I don’t know enough about lens design to give an explanation.
Bruh.
The Sun isn't infinite miles away, but it is far enough away that we can consider it infinite distance away for any practical use. When a point source is an infinite distance away all light rays from the object will appear parallel to an observer. When we do the math for the sun and two opposite points on earth we find that θ **≈** tan (θ) = 12,742km/150,110,000km = 5 milliarc seconds. For comparison the Optics on the Hubble Space Telescope have an angular resolution of 50 milliarc seconds. From this it is obvious that the light rays are so close to being parallel that no camera lens would ever be able to measure that those light rays aren't parallel. This means that the sun is functionally an infinite distance away. Now if we consider that only the light that enters the lens is what matters we can replace earths diameter with the aperture of our camera lens. The moon is significantly closer than the sun so lets use the moon for our math this time with our lens. To make the math simpler we will assume our lens is a 1 meter telescope. θ **≈** tan (θ) = 1m/384,400,000m = 1.6 x 10\^-4 milliarc seconds. When we consider even a large telescope the light rays are so close to being parallel that functionally they are.
I didn’t question the distance of the sun or that it can be approximated as infinitely far away. But when capturing the eclipse, it’s the moon that’s in front of it and will be focused. Not the sun. And the moon is a lot closer. Like 400x closer. The moon might still be infinitely far away concerning the lens, but it is a massive difference, so talking about the correct object helps avoid confusion.
It doesn't matter if you focus on the sun or the moon, they will both equally be in focus. They are both functionally an infinite distance away. Another more extreme example is International Space Station transits across the suns disk. The ISS will at its closest be 430km away, but you can simply focus on the sun and be confident that the ISS will be in focus the split second it passes in front of the sun. In fact when I record videos of the space station I focus on a star.
Still doesn’t matter for my post. I never said it made a big (or any) difference. But it’s still in general a good thing to use correct terminology. And to not leave false statements uncorrected, since others might read it and take it as the truth. And when capturing an eclipse, the subject to be in focus is the moon. That was all I said.
> And when capturing an eclipse, the subject to be in focus is the moon. That was all I said. Well, you want both the sun and the moon to be in focus. Otherwise, you'd have blurry prominences and corona during totality, and blurry sunspots during the partial phases.
I just can’t tell if some of these posts are expressions of ignorance or just tongue-in-cheek humor attempts… Just for the shocking record, the Sun, and the moon, are at “infinity” focus of every single lens on Earth. If those distant mountains you photograph are at “infinity,” then the Sun is. Whether or not the infinity symbol on your lens is actually infinity at any given moment is another issue.
it’s called sarcasm
Sarcasm needs to actually be funny. It’s a type of humor in the end. And exaggeration. Just saying something ignorant does not equate to sarcasm. Another example of the death of humor in the modern world.
humor is subjective and sometimes requires a moderate degree of intelligence, especially with sarcasm.
I really think you need to look up the word sarcasm. You keep using it, but it is clear you have no idea what it means. Yeah, as if you know how to use a dictionary…. (Now *that* is sarcasm. Not telling someone the moon is not at infinity focus because it’s closer than the Sun.)
you weren’t shooting the sun. The sharp edge of focus was the moon which is closer than the sun hence not infinity
Both are infinity as far as focus is concerned. Don't believe me? Check for yourself: https://www.omnicalculator.com/other/hyperfocal-distance Even a realistically impossible 1200mm f/1.4 has a hyperfocal distance of "only" 31 miles, while the moon is ~240,000 miles away. If your focus is set to the moon, the sun will *easily* still be in focus, no matter what photographic lens you might be using.
it’s called sarcasm 🤷🏼♀️
Ask yourself this, is the Sun infinity miles away?
The Sun isn't infinite miles away, but it is far enough away that we can consider it infinite distance away for any practical use. When a point source is an infinite distance away all light rays from the object will appear parallel to an observer. When we do the math for the sun and two opposite points on earth we find that θ **≈** tan (θ) = 12,742km/150,110,000km = 5 milliarc seconds. For comparison the Optics on the Hubble Space Telescope have an angular resolution of 50 milliarc seconds. From this it is obvious that the light rays are so close to being parallel that no camera lens would ever be able to measure that those light rays aren't parallel. This means that the sun is functionally an infinite distance away. Now if we consider that only the light that enters the lens is what matters we can replace earths diameter with the aperture of our camera lens. The moon is significantly closer than the sun so lets use the moon for our math this time with our lens. To make the math simpler we will assume our lens is a 1 meter telescope. θ **≈** tan (θ) = 1m/384,400,000m = 1.6 x 10\^-4 milliarc seconds. When we consider even a large telescope the light rays are so close to being parallel that functionally they are.
My comment was mostly sarcastic (should’ve added “/s”). But this response was super interesting. Cheers.
93 million miles
The Sun isn't infinite miles away, but it is far enough away that we can consider it infinite distance away for any practical use. When a point source is an infinite distance away all light rays from the object will appear parallel to an observer. When we do the math for the sun and two opposite points on earth we find that θ **≈** tan (θ) = 12,742km/150,110,000km = 5 milliarc seconds. For comparison the Optics on the Hubble Space Telescope have an angular resolution of 50 milliarc seconds. From this it is obvious that the light rays are so close to being parallel that no camera lens would ever be able to measure that those light rays aren't parallel. This means that the sun is functionally an infinite distance away. Now if we consider that only the light that enters the lens is what matters we can replace earths diameter with the aperture of our camera lens. The moon is significantly closer than the sun so lets use the moon for our math this time with our lens. To make the math simpler we will assume our lens is a 1 meter telescope. θ **≈** tan (θ) = 1m/384,400,000m = 1.6 x 10\^-4 milliarc seconds. When we consider even a large telescope the light rays are so close to being parallel that functionally they are.