Author Topic: Magnification changes as FPS changes  (Read 2519 times)

rdemyan

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Magnification changes as FPS changes
« on: December 09, 2020, 12:39:13 PM »
Can someone please help me understand how the magnification changes as the FPS changes. I think that a FPS setting of 1280 x 720 on the Chronos 2.1 color camera means that the frame is 1280 (pixels??) wide by 720 high.  Is my thinking here correct?

If I change it to 1280 x 240, then the image is magnified because the vertical  height is reduced.  Is that correct?  If correct, there should be a fair amount of magnification.  Is there any way to calculate the amount of magnification?

If I reduce the width from 1280 to say 640, then does that also increase the magnification in addition to any magnification increase due to decreasing the height?

I need to get a lot of magnification because I'm doing macro filming of sprays. Right now the extension tubes have the lens too close to the subject and it keeps getting very wet.

Any help is appreciated.

Thanks.

Nikon1

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Re: Magnification changes as FPS changes
« Reply #1 on: December 10, 2020, 07:02:44 AM »
Magnification will in fact never change from only a Resolution Change (at least not on this camera), if Lens, Zoom (if there is any), Focus and Distance to object isnt Changed.
 Given A Fixed Magnification Ratio, for example 1:1 for simplicity (which would remain the Same at any time, like asumed above, as nothing is changed), at an Sensor Size of 19,2x10,8mm Of the Chronos 2.1 at full Resolution, an Object or Area of 19,2x10,8mm will always fill the Frame (or more correctly is projected onto the Sensor to fill the Frame, so if Mag. Ratio is exactly 1:1, this is How much you will see.).
 This means, that the Area that is "covered" by an single Pixel will allways stay the same, at 1:1 Magnification Ratio and an Pixel size of 10Ám on the 2.1 an single Pixel will allways Cover 10Ám (0,01mm) Area of your Object or Area in Frame.
 .
 Now, when you change Resolution, This Optical Process of projecting your Object *at whatever Magnification Ratio you are at* onto the Sensor at the Same Size at all times will still happen, the only thing that changes is that you now use Less pixels, meaning also less Sensor Width and/or Height. So if you would actually overlay the Smaller Resolution shot onto the Higher Resolution shot Pixel over Pixel (not Streched to fit the Same canvas!), actuall Magnification would allways stay the same (you wont get any more detail out of lower Resolution Shots, as one Pixel will allways cover the Same Space, limiting the Resolution). What changes is Field of view as some people call it or "Region of Interrest". What that means is that just not all of the Image is used, resulting in an more narrow field of view. If now a lower Resolution Shot is Streched to fit the Same final Size as an Full Resolution shot on this Camera, obviously the Object or Area Shown will seem Bigger. But this is about the Same as cropping the Frame on a PC in editing, wont really change the actuall Magnification or give you any more detail on a Pixel by Pixel base.
 .
 To calculate the Actuall Optical Magnification (if that is what you wanted to know), Figure out whatever effective Sensor size you are using (it is easiest to calculate at full resolution, as the Nominal full Sensor size is known (see Datasheet), while the effective Used Sensor Area needs to be calculated depending on used resolution), and shoot some Ruler or anything else of known dimensions, and Either get an Reading of the Object size/ Exact distance that will fill Height or width of the Frame, or get an Reading of how many pixels something of known dimensions will fill. Depending on that, as Pixel size (is known)/ Sensor Size (is known for Full Resolution / Can be calculated for Smaller Res.), an Ratio can be Calculated by dividing one by the other Lenght, giving you an (optical) Magnification Ratio.
 .
To Calculate the Field of view at given resolution (basically the Same kind of calculation needed as when trying to figure out you effective Sensor size/ diagonal) you first need a reference point, for example a known Magnification Ratio or known Field of view/ Distance, if you want your result to be in Absolute Numbers (if you want to know how much mm of effective Frame Diagonal is Shown at an given Resolution), if you dont have a reference point, your result will allways be an Ratio (as the Full sensor size is the Only thing known, if nothing else is given/ known. Result will basically be like: At x Resolution the frame will seem y times bigger than at full resolution if stretched to fill the Same space (depending on whatever you are After, you will need to calculate that Ratio/field of view based on Horizontal / Vertical /diagonal Base, as they can result in very different values in some Cases, especially if your Aspect Ratio (=relation of Image Height to width) is Changed dramatically between the Two)).
 So for example to Calculate the Horizontal Field of view/ Sensor Size for 1280px Image Width on the 2.1 Compared to Full Sensor Size, you need to either Divide the Full Resolution (1920px) by 1280px, to get an Crop Factor or increase of object size when final image Is Stretched to same Dimensions for that Axis of the Image. This would result in an Factor of 1,5x (Which in the Case of 1280x720 would be the Same for Horizontal, Vertical AND Diagonal Dimension, as Aspect ratio is the Same as 1920x1080, both are 16:9). Now this Horizontal Crop factor / Ratio of Field of View/ "additional Magnification" would be the Same for 1280x1080, 1280x720, 1280x640, 1280x240 or any other Vertical Resolution, if lens and Camera /object Position are untouched.
 Vertical and Diagonal Field of view will obviously change quite a lot between all the Settings above but can be Calculated the Same Way by simply dividing one by the Other and Applying the resulting Ratio to whatever Known Dimension you have (Sensor Size, some object in Frame, ....) or using the Ratio Straight away.
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 As far as Calculating Diagonal Sizes of any kind, no matter if Sensor Size, Resolution, Object Size or Field of view; there is allways a^2+b^2=c^2 (a Squared + b Squared is c Squared, PythagorasTheorem) where "a" and "b" are horizontal and Vertical Dimensions and "c" would be your diagonal Dimension. Works for Absolute Numbers as well as Ratios.

Nikon1

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Re: Magnification changes as FPS changes
« Reply #2 on: December 12, 2020, 03:33:04 PM »
So what you are looking to do is to maximize your Optical Magnification, from what i understand.
 Now there is generally two ways to do that.
 #1 is to increase Focal Length (or zoom in if you have a zoom. But generally, most longer Focal Lenght lenses wont focus that close, mostly due to the Fact that lenses would get incredible Bulky if they could, for reference also see my next post.)
 #2 is to get Closer. no matter what focal length you use (as long as you dont use some weird telecentric Lens or something), if you will get closer, Magnification will increase. Problem here is, that its sometimes physically impossible to get closer, because of certain limitations, like Lighting and Size of object and Lens/ Camera. Also most lenses Wont even Focus that close that touching the Object you shooting would even be possible in the First place.
 Given that it seems like you cant get any closer, what you propably want to do is something like Long-Range Macro (if something like a Macro-Probe Lens (there are Plenty of those that are fully waterproof) isnt an option to get closer or is still too little Magnification).
 

Nikon1

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Re: Magnification changes as FPS changes
« Reply #3 on: December 12, 2020, 03:48:12 PM »
So for anyone interrested, here is a quick lesson in Long-Range Macro:
 Take an VERY Sharp Tele Lens, focal Length Depending on whatever Magnification and Working distance you are After (and also depending on the Size Limitations of your Camera Contraption, if there are any, for example room size).
 Now add some serious amount of Space between That Camera and said Lens. final Position of Object from Lens and Distance from Lens to Camera need to be figured out by Trial And Error (Depth of field is crazy small with stuff like that, so some kind of Macro slider to control the Exact position would for sure be of great use, if you are unpatient).
 Find a Way to mount and align the three of those things somehow.
 Then find a Way to block the Light from the outside hitting the Camera sensor, else you propably wont see anything at all. Thick Cardboard tube will do, and a lot of other things will also, if you want to be fancy, use propper Macro tubes or get yourself some Made Custom, because you cant by those in any kind of store i know of (you now have entered some rabbit-Hole of Photography, which even most Photographers didnt even know of, so some DIY will most likely be involved).
 Add a ton of light, you will need it! the Longer the Tube gets, the Darker your image will be, even if Light and Iris is unchanged!
 Congratulations!
 You now have a macro lens with some really long working distance and an Absurdly huge camera rig...

Nikon1

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Re: Magnification changes as FPS changes
« Reply #4 on: December 12, 2020, 04:18:54 PM »
I just did some kind of Proof of Concept here and put my old Nikkor AF 70-300mm On a stick and put like half a Meter of Cardboard tube as a Macro Tube on there. Works out to about 0,6m working distance, which i hope would be enough for water splashing and stuff?
Since this lens isnt even Really sharp to beginn with for Regular use (this was made when Film Cameras where still a thing, and even back then it wasnt really the greatest lens), it only gets worse with stuff like this (with increasing the Distance between camera and Sensor, you basically increase the Size of the Image the Lens Generates on the Sensor side, and still only using the Same Area as your sensor usually would be, now with doing that, that doesnt really help the lens, if its allready bad, since it will make just everything bigger, like Chromatic abberations and stuff like that, which then will be a lot more visible in the Final image).
 .
 So i used my Nikon1 J5 for that, because i was really not in the mood to do this with the Chronos today, for a bunch of reasons. Also, this following example is just a Proof-of-Concept to proove a point here, i know its not that great of an Final Image (as i said, most of it comes down to the Lens not beeing too sharp and me using it wide open here, also a bunch of dirt on the Sensor from fumbling around with Paper tubes in front of an exposed sensor for like 40Minutes...).
 Lens settings where 300mm and f/5.6
 I shot a Match, which was about 3mm in Horizontal size. This came out to be about 3620px wide on the 5568px Wide Image on an horizontal Sensor Size of 13,2mm. This means, that the Mach was Covering about 8,582mm Of the Sensor in Horizontal Direction. If compared to the Real size of the Match head, which was 3,03mm this works out to an Optical Magnification Ratio of around 2,86:1 ; Which means, that the image of the match is projected onto the sensor in about 3x its real size.
 The rig i set up for this test was pretty sketchy (but still not the worst thing i have done), but works. For real world use/ actuall work with something like this, i would propably want to use a much better and Sharper Lens than this one, and some better mounting of the Parts.
 .
 I dont know what kind of Magnification you are on right now, but if i would have to use it myself, i would try to figure out what kind of working distange and Magnification i am Aiming at, and maybe even use a Shorter lens than Straight up an 300mm, but if you really need actuall Magnification beyond 1:1 and some serious Working distance, you usually wont get around long focal Lenght Lenses and Bulky camera Rigs (unless you get some Seriously expensive lenses, there are some for industrial Applications, but those are far from affordable usually).

Nikon1

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Re: Magnification changes as FPS changes
« Reply #5 on: December 13, 2020, 03:55:21 AM »
so to see this a bit more in relation, lets also have a look at some More common approaches to Macro beyond 1:1 optical Magnification (without getting an propper dedicated Macro lens that can allready get you at the desired Magnification).
 The most common approach i could think of are just regular Macro tubes with Some Shorter Focal Lenght or Portrait Lenght Lens, usually primes. Those are readily available to buy (even in some photpgraphy stores) and widely used for that (or even to push your macro lens further).
 Did a quick Shot of that Same Match with 65mm of Macro tubes and my Trusty 32mm 1Nikkor Lens. That would be compareable to something like a 50mm lens on the 2.1 on full Resolution (or 32mm on the 2.1 @ 1280x720). Was able to get to 1,87:1 Optical magnification with that, but lighting that was allready becoming a problem, because lens was really close to object allready. Setups like this can usually be used from 1:4 up to 2:1 with good results, but generally lack A lot of working distance for the Higher Magnifications (Short range Macro). i also attached the final shot from that (shot at f/16), to give some idea of what kind of detail can be captured with an actually decent lens.
 

Nikon1

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Re: Magnification changes as FPS changes
« Reply #6 on: December 13, 2020, 04:13:17 AM »
Then there is Retromounting (turning the lens around, so the Side that usually points towards the Sensor is now looking at the Object you are shooting), usually done with shorter Focal Length lenses or even Wide Angle Lenses. While there are also some Reto-Adapters available to buy they are used way less and also not too widely known, from what i have seen. Again, if you know what you are doing tape will also work (tape and Glue are allways your best friends when you dont have propper adapters on hand). Here i used my 12,5mm Avenir Lens, would work out to be around 18mm on the 2.1 when full sensor is used i assume (to lazy to calculate rn...). Just for good meassure i also put the 65mm Stack of Extension Tubes behind it, and got to about 7,7:1 Magnification Ratio (Shot a grain of salt, but dropped it when i tried to meassure it, and couldnt find that exact one again, but they seem to be around 0,5 to 0,6mm In size from meassuring a bunch of other ones). Now this has a depth of field so thin that it is almost non-Existent, even at f/16, which is very common if you get into really extreme Macro stuff. I assume you can push such a setup to 10:1 Ratio if you wanted to, with still acceptable results, but again, at some point Working distance will propably become an issue. However, this kind of approach usually still gives you a bit more working distance at the higher Magnifications than Macro tubes, unless you use pretty long focal lenght lenses for it.
 .
 As i allready explained earlier, for really long working distance at higher Optical Magnifications, you usually end up needing some kind of huge tube or bellows and a long lens (long-Range Macro).

Nikon1

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Re: Magnification changes as FPS changes
« Reply #7 on: December 13, 2020, 04:24:03 AM »
If 10:1 is still not enough Optical Magnification, i would reccomend looking straight into actuall Microscopy Lenses, for some of them There are even Adapters and Bellowes available, or just Mount your Camera to an existing Microscope and use it that way, there are also adapters for that. But as you go up in Magnification, Depth of field usually gets thinner and Thiner, also the tinyest bit of Flex in your rig will end up completely Shaking up your image, especially at 10:1 or Microscopy Levels of Magnification (feels like shooting 2000+mm Tele Lenses, if you ever did that, just starts Shaking from You watching it...). I am not going to explain this in depth here, because Microscopy itself is an whole new topic on its own, and i myself also dont really have a ton of experience about it (i mostly came along pretty well with Magnifications up to 5:1, and didnt need to go much further so far), but there are a bunch of people here in the Forum that use a Chronos on an Microscope, so they maybe know a thing or two, i dont know. So let me know if i or anyone else who knows a bit more about that should go into depth about that.