Author Topic: Extracting still images  (Read 933 times)

LimaKilo

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Re: Extracting still images
« Reply #15 on: May 02, 2020, 01:54:51 AM »
Is there a reason not to trust the camera when it says 1 microsecond?

Verifying the exposure time with simple equipment will be difficult, because 1 μs is just really fast. If you put a 50 mm radius disk on a rotary grinder like a Dremel, at 30k RPM the edge will only travel 0.15 mm in one μs. A bullet flying at speed of sound will travel less than 0.5 mm in one μs.

If you have an oscilloscope, you could try to get a LED to blink for 1 μs and check the pulse length with a photodiode (make sure to check that the LED doesn't phosphoresce like some white LEDs will do).
« Last Edit: May 02, 2020, 02:05:30 AM by LimaKilo »

NiNeff

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Re: Extracting still images
« Reply #16 on: May 02, 2020, 09:06:24 AM »
The camera has a frame-sync output. if you really need to check it, hook an ozilloscope up to that. However I don't see any reason to no trust the camera.

Photopage

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Re: Extracting still images
« Reply #17 on: May 02, 2020, 06:54:54 PM »
"The 2.1 can shoot with exposures down to a micro second.  I just tested it."

I've pretty much decided that I am going to buy one of the cameras.  The datasheet for the 2.1 says that the minimum exposure time is 10 microseconds and not 1 microsecond.  Would you please confirm that you were able to get 1 microsecond?

Also, is the fps really limited to 24,046 per the datasheet?  It seems odd for a higher resolution camera and given that the initial announcements for the 2.1 said the camera would be able to shoot 100K fps.

Thanks.


To test the 1 microsecond exposure I shot a 260mm diameter saw blade doing roughly 1800rpm.
To test the timing using household equipment only, I compared the distance between frames at 24000fps with the motion blur of the exposure at 1us.
jpeg of frame sequence attached
I know that this relies on the same piece of kit to both test and measure, but no-one is questioning the frame rates.
Looks good to me.
I also shot at 5000fps and got the same result, but there is no usable sequence at this micro scale, jpeg attached.
 

rdemyan

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Re: Extracting still images
« Reply #18 on: June 22, 2020, 12:01:56 PM »
Hi Photopage:

Sorry for the late reply.  Thanks for taking the time to try to verify the exposure.

In looking at the pictures, I am confused.  If each still is one microsecond exposure, why aren't the images much clearer.  In looking at the images, I have no idea what I'm looking at.

Thanks.

Nikon1

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Re: Extracting still images
« Reply #19 on: June 22, 2020, 12:09:02 PM »
Hi Photopage:

Sorry for the late reply.  Thanks for taking the time to try to verify the exposure.

In looking at the pictures, I am confused.  If each still is one microsecond exposure, why aren't the images much clearer.  In looking at the images, I have no idea what I'm looking at.

Thanks.
Well, its High Magnification, and you need crazy good lenses, to get REALLY sharp images at High Magnification ratios.
 Almost any usual lens will give rather blurry results and/ or other image Artifacts, such as color abberations.
 From what i can Tell, field of view is smaller than 5mm, which is pretty high magnification compared to most every-Day Photography or Video.
 Not sure, if thats all, but i think its a considerable part of the Reason, why the image Quality is rather low.
 Also lighting can get difficult for such kind of scenarios, not only because Macro needs a lot light on its own, but because you can easily run into problems to actually get your Lamps and Lenses close enough and such.
 And a ton of other challenges of high-Magnification, high framerate Shooting.

rdemyan

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Re: Extracting still images
« Reply #20 on: June 22, 2020, 12:36:05 PM »
Hi Nikon1:

I will most likely be buying the Chronos 1.4 (black and white) in July.  Which lens do you recommend for my needs.  Is there an adapter that will allow me to use the Nikon 50 mm prime that you recommended for my photo camera and which I do have.  As you know I need sharp images.

Also, do you have any recommendations for video editing software that provide excellent sharpening and noise reduction.

Thanks.

Nikon1

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Re: Extracting still images
« Reply #21 on: June 22, 2020, 01:02:37 PM »
https://www.bhphotovideo.com/c/product/1150822-REG/fotodiox_nkg_af_c_pro_lens_mount_adapter.html
 .
For the Adapter, i would reccomend this Adapter Above for Any Nikon AF-S Type Lenses without apperture Ring..If you want to get even more Magnification out of your 50/1.8, maybe try using it inverted with an Retro-Adapter like this (make sure to get one with an 58mm Thread on it, since it will not fit the AF-S 50/1.8 otherwise without an additional adapter, also make sure to find a way to keep the Apperture open, since the Apperture-Control tab on the Back of the Lens is then just free, and Apperture will close down completely to f/22 or something):https://www.ebay.de/itm/Retroadapter-Nikon-58-mm-Makro-Umkehrring-Reversering-Objektiv-Makroadapter/254269005019?hash=item3b339d1cdb:g:fX4AAOSwNrtdCkEo
 .

 This Retro-Adapter will help you get higher quality images at very high magnification ratios, like the shots with field of view of only a few millimeters (talking around Magnification 1:1 and beyond, 1:1 Magnification on the 2.1 will give a field of view of 19,2x10,8mm if the Full sensor is used). This can also be combined with the Macro-Tubes you allready own to get even Higher Magnification, but you will end up with your lens very near to the Subject of interrest.Since i know you work with Liquids and would like to have more distance to Subject, you need higher Focal length for more distance.Basically the two options you have for a Macro lens with longer Focal length are to get an actuall Macro lens, i would reccomend something with 100mm or even longer, if you can find anything good with longer focal lenght for reasonable price. Calculate Magnification you try to achive based on your Subject size compared to sensor size and check the Lens, if it is built to do that kind of magnification.
The other option is a bit more complicated, using Enlarger-Lenses and Macro-Bellows. This can get a bit more Expensive, but you can find them in longer focal length more easily (most are however Vintage and not very sharp or they get expensive rather Quickly, but there are really affordable and good ones out there).

rdemyan

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Re: Extracting still images
« Reply #22 on: June 22, 2020, 01:55:28 PM »
Interesting that when googling the retroadapter ring, most of what comes up is from Germany.  Even on American eBay I only saw these rings, by themselves, sold from Germany. Further, virtually all of the videos  explaining the concept that result from a search are in German. Not that it matters, just curious if American sellers do not support this type of ring or is there some other reason. 

Anyway, I watched a German video where the guy compared this retroadapter ring with the raynox dcr-250. I understood most of it although I'm not familiar with  most of the "camera-specific" German words.  If I understood correctly, the raynox dcr-250 just snaps onto the front of the lens and does not mess with the contacts, so I can continue to set the aperture as I do now.  The retro adapter requires the lens to be reversed, which seems strange, but I guess also means that I will have an issue with the aperture since my 50 mm lens does not have an aperture ring.  What's your opinion of the raynox dcr-250?  Below is a link to the video I watched.

https://www.youtube.com/watch?v=x6s3MlzwdZg

https://www.youtube.com/watch?v=x6s3MlzwdZg

Nikon1

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Re: Extracting still images
« Reply #23 on: June 22, 2020, 02:44:30 PM »
Interesting that when googling the retroadapter ring, most of what comes up is from Germany.  Even on American eBay I only saw these rings, by themselves, sold from Germany. Further, virtually all of the videos  explaining the concept that result from a search are in German. Not that it matters, just curious if American sellers do not support this type of ring or is there some other reason. 

Anyway, I watched a German video where the guy compared this retroadapter ring with the raynox dcr-250. I understood most of it although I'm not familiar with  most of the "camera-specific" German words.  If I understood correctly, the raynox dcr-250 just snaps onto the front of the lens and does not mess with the contacts, so I can continue to set the aperture as I do now.  The retro adapter requires the lens to be reversed, which seems strange, but I guess also means that I will have an issue with the aperture since my 50 mm lens does not have an aperture ring.  What's your opinion of the raynox dcr-250?  Below is a link to the video I watched.

https://www.youtube.com/watch?v=x6s3MlzwdZg

https://www.youtube.com/watch?v=x6s3MlzwdZg
I also had trouble to find anything according to Retrofit-Adapters for Lenses in english, but knew about them for Years. Seems to be a german thing, maybe the orgin is Novoflex, a german company, that still exists to this day, they came up with a ton of strange and obscure Camera Adapters and such, aswell as all the other German Optics Companys, which had been and still are making some Special Stuff i never seen anywhere else. 
 So i just linked to the German Ebay. 
 .
I generally am not strictly against diopters as the one you mentioned (but never heard about it, and also havnt watched the Videos about it), but they do lower your Image Quality.  I will try to explain it like this: A optical system is generally optimized and built for one particular use, in the Case of something like the 50mm 1.8 AF-S, its a Rather sharp Normal short-Focus Gauss-Type Lens for 43 to 28mm Image Circle, meaning it will perform best on DX-Format Nikon Cameras and FX-Format Cameras with Focus from Infinity to around 50cm Distance. but since its image Quality can only truely optimized for one particular distance, its mosly somewhere Between infinity and 0.5 Meters, at wich it will perform BEST. It will, for most situations still perform "good enough" at infinity distance and close Focus distance 0.5m.
 Now if you go really close, like 0.1m or closer, on some Lenses Image Quality will significantly drop, because the Lens is just not meant to do that. You CAN build lenses, which are not affected as much by focus distance, or just are better optimized for closer focusing distances, such are actuall macro lenses (beware of lenses with "MACRO" in the name or ones that just state they are macro, most are technically not, Macro starts at 1:1 Magnification, and a lot of lenses which Have Macro in the name dont come Close to that, so always look up, what kind of Magnification the Lens is built for), but that usually makes the Lens more expensive, and since by far not everyone needs a lens that can do this kind of stuff, its usually left out or worked around in a way to work somewhat acceptable for general use. They are either Calculated in their designs to have about the Same image Quality independent of Focus distance or will be optimized for a Rather Close Focusing point, at which they will perform best, those may not give best image Quality at Infinity Focus for example.
 Now, every optical System (For this matter read "Lens") is optimized in it self to produce a image as good as possible as given By the Price Point and other criteria considered by the Designer, such as Zoom Range, available Glass-Types, Weight, Sharpness, Lens Speed and quite a few more. If you now add an Additional Optical Element to the Front, you kind of mess up the Optical System. Those Diopters are usualy made to fit a large range of Lenses, and therfor will never be a perfect fit to any of the Lenses and lower image Quality. There are a few Diopters especially designed for certain lenses, but most are universal. That beeing said, some Lens-Diopter Combinations can still work well, and i actually use a pair of really Old russian Diopters with good coatings of to-me-unknown-brand which give superb Image Quality in combination with my 32mm 1.2 1Nikkor, which is mostly used for Product-Shots. The diopters cover the Magnification ratio nicely, which i cant really can get with the Lenses Natural Close-Focus distance and for which the Macro tubes are too high Magnification allready. Those Two diopters (+1 +2) really nicely fill in that Gap and give me a Magnification Range from Infinity down to the Point where i can fill the Frame with an Ant.
 These Old russian Diopters give good enough results for me, and you cant really tell any drawbacks in image Quality when using them on this lens, but (the only other ones i ever tested) i also bought a bunch of Cheap (~30 or 40 for a Set of 5) China diopters New, those are just bad, no matter what lens they are used on. As Far as i can tell, they are not even Coated.
 So in generall, Diopters are Worth a try if you really need to, but it will always be a compromise in image Q.
 .
 Now about the "Strange" Idea of just flipping a lens inside out to get higher Magnification ratios. As i explained in the beginning of this Reply, a lens is optimized for a certain Magnification Ratio, which could, for a lens like the AF-S 50/1.8, be something like Waist-Head Portrait-Distance on DX or full-Body Images on Full-Frame, which should be about the Same distance. Now Lets assume Horizontal Field of view for this would be about 80cm and Horizontal Sensor Width would be 23,5mm (Nikon DX), then your Magnification would be something around 1:30. That means the Lens is Optimized to render an big image onto a 30x Smaller Area. now since the Image in the Sensor Plane is calculated to be color-Corect and otherwise intact, the Lens can witout any problem be inverted, meaning it will now work best for rendering something small 30 times bigger onto the Sensor. This is actually really extreme, and i dont know, if the 50/1.8 will still perform that well at that Magnification, but the Principle works about like this. Lenses Dont really care, which direction the Light goes, thats why you can use most Projector lenses for image Capturing as well!
 Its not that Strange, if you think about it twice and understand, whats going on. Most lenses Are just usualy built to project something Rather Large onto a Sensor, which is usually a lot smaller than the Object its Trying to capture, and the Lens is made to perform best for those situations. If you try to capture things of the Size of your Sensor or smaller, you then either need special optics made for that purpose, calculated to perform best in this kind of scenario, or flip a lens and make it project the other way around.
 .
Hope this was kind of understanable of an Explaination about the Retro-Adapter-Thing.
« Last Edit: June 22, 2020, 02:50:15 PM by Nikon1 »

rdemyan

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Re: Extracting still images
« Reply #24 on: June 22, 2020, 03:38:30 PM »
Yes, thanks for the explanation.

What about setting the Fstop if I use a retroadapter?  How am I going to do that since the lenses I have do not have aperture rings?

Here's a video of a guy who compared the Raynox DCR 250 with extension tubes and with a macro lens.  He thinks the sharpness is very good, although the macro is a bit sharper.

https://www.youtube.com/watch?v=mYRZsmsI5Ec

Nikon1

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Re: Extracting still images
« Reply #25 on: June 22, 2020, 03:50:26 PM »
There Are Professionaly made Adapters for Canon, which will just connect the [now in Free Air] Contacts of the Lens with the Original contacts with the Body with a Cable, but since The G-Style Lenses without apperture Ring also Require Mechanics, i seem not to be able to find any of those for Nikon F G-Style.  However, there ist this (Also german again, sorry):
 http://www.fdm-ware.de/Retro/retro7.jpg
 http://www.fdm-ware.de/Retro/index.html
 .
 if that doesnt work, when in doubt, use this:
 http://forum.krontech.ca/index.php?topic=516.msg2836#msg2836
 .
 Or come op with something else yourself, its just a lever opening the iris.

rdemyan

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Re: Extracting still images
« Reply #26 on: June 22, 2020, 03:55:42 PM »
Thanks.  You are someone who has decades of hands-on experience, whereas I am a total novice.  I don't want to damage my lens by trying some of these things.

I could still try the to use extension tubes with my lens on the Kronos 1.4, couldn't I?

Nikon1

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Re: Extracting still images
« Reply #27 on: June 22, 2020, 04:10:51 PM »

I could still try the to use extension tubes with my lens on the Kronos 1.4, couldn't I?
Sure, you can use anything you would be able to use on the Nikon Camera, except autofocus and such.
 I also searched a bunch more, and found some seemingly propper solution for the Iris Problem with Nikon lenses.
 Search up "reverse protect ring nikon" In an Search engine or "Nikon BR-6", those are propably the most propper way to do retromounting of lenses, that i found so far. The Reverse Protection ring will allow you to mount an Clear Filter in front of your lens assembly, so that the part thats usually inside of the Camera isnt exposed to the elements or your liquids. Just mount an Standard clear Protection filter there. The BR-6 does even more and seems to allow for full control of the Apperture via an lockable meachanical cable remote. not 100% sure, if the BR-6 also allows for Filters to be mounted, but i would hope so, since its original Part from Nikon? You would need to do your own research on that, if you are really interrested in this BR-6. Otherwise There Could be Diopters, which are kind of good out there, as mentioned my Russian ones, and i also never really tried higher priced new ones, but anything that avoids putting additional optics in front or behind your lens should generally give sharper and higher Quality images, given an High Quality Lens to beginn with. So Macro tubes and Retro-Mounting Lenses is usually the way to go, if a dedicated macro lens is for some reason not worth owning or to expensive.

Photopage

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Re: Extracting still images
« Reply #28 on: June 24, 2020, 02:30:26 AM »
Hi Photopage:

Sorry for the late reply.  Thanks for taking the time to try to verify the exposure.

In looking at the pictures, I am confused.  If each still is one microsecond exposure, why aren't the images much clearer.  In looking at the images, I have no idea what I'm looking at.

Thanks.

Hi rdemyan,
 I was using motion blur to work out the exposure duration.  No motion, no information.  So you are looking at a highly magnified image of a saw blade going at roughly 2000 rpm.  See attached jpeg for wide view.  Also, there was a good discussion about the differences in 2.1 and 1.4 sensors and how they deal with parasitic exposure.  You are right to choose the 1.4 for shorter shutter speeds.