Do I need a telephoto lens or a macro lens?

Started 2 months ago | Discussions
Hossein93 New Member • Posts: 3
Do I need a telephoto lens or a macro lens?

Hello,

I am spreading the metal powder particles with different spreading speeds on a flat surface; it means one blade, which has a H= 50 um gap with the surface, will spread the powder particles, which are like a powder pile in front of the blade, on the surface. Thus, the powder particles will be in a very fast motion to pass through the gap and be deposited on the surface. For having an idea of what I am referring to, please see the below picture:

  1. Chen, Q. Wei, S. Wen, Z. Li, and Y. Shi, “Flow behavior of powder particles in the layering process of selective laser melting: Numerical modeling and experimental verification based on discrete element method,” Int. J. Mach. Tools Manuf., vol. 123, pp. 146–159, Dec. 2017.

I need to take some pictures of powder particles with sizes of around 20 microns. I have an SC1 Edgertronic camera which can be found here. The location of the camera is shown in the above picture but the camera is actually connected to the side of the blade and is moving with it. Thus, the avalanches that the powder creates can be observed with the camera. An image of what I am referring to is shown below:

This is the Zoomed-in image of the above one (I know the fame # is different, but it is basically the same but at a different time).

As can be seen, the distance between the powder and the camera is large and the powder particles cannot be observed and tracked. I need a lens that is capable of getting the track of particles. As I mentioned earlier, this event is happening so fast, so I needed to use a high-speed camera like this. I do not need the features on the surface of powder particles; I only need to see how fast they are moving and what angle is the powder pile creating with the surface (the angle can be observed in the above picture).

Please answer the below questions:

1- Do you know whether I need a telephoto (zoom) lens or a macro lens? I have been searching the Internet for a while, but I 've got kind of confused. Sounds like the telephoto lenses would just get close to the subject while losing the focus; the macro lenses, however, would have a reproduction rate of at least 1:1, which would present a sharp image of small creatures. I have to mention the camera is only compatible with the F mount Nikon series lenses; so, is there any way I can convert other lenses to the F mount or somehow figure this limitation out?

2- I think I need some kind of backlight illumination for these pictures to be able to see the particles in a way that they cannot be mixed up and be tracked pretty easily. Can you help me with the suggested backlight illumination for this project? Also, for backlight illumination, I need to have a light diffusion screen and non-flicker light source as well; what light diffusion screen is more recommended? What about the non-flicker lamp?

3- Do you know anyway or software that could count the time and place it on the pictures, just like the frame number, ISO, EXP time, and FPS as shown in the below picture?

Since I need to have the particles in larger sizes on the camera's sensor, I was thinking I need a macro lens, but I was not sure. So I asked my question here to use the knowledge and experience of experts.

I should mention I am new to photography.

Any help would be appreciated.

Thanks!

BBbuilder467 Veteran Member • Posts: 4,578
Re: Do I need a telephoto lens or a macro lens?

If you think of your 50mm lens as normal, a 90mm lens is a telephoto. It's magnification could be the same as you have, but from farther away. You won't gain anything but working distance.

A 90mm macro lens would be capable of about 5 times the magnification at it's minimum focus distance. That would be 1:1 at the sensor.

What wasn't clear on the other forum is how much your video crops the image.

You seem to need some specific working distance from the lens to subject and that has to be factored in.

John K Veteran Member • Posts: 8,649
Re: Do I need a telephoto lens or a macro lens?

Hossein93 wrote:

Hello,

I am spreading the metal powder particles with different spreading speeds on a flat surface; it means one blade, which has a H= 50 um gap with the surface, will spread the powder particles, which are like a powder pile in front of the blade, on the surface. Thus, the powder particles will be in a very fast motion to pass through the gap and be deposited on the surface. For having an idea of what I am referring to, please see the below picture:

  1. Chen, Q. Wei, S. Wen, Z. Li, and Y. Shi, “Flow behavior of powder particles in the layering process of selective laser melting: Numerical modeling and experimental verification based on discrete element method,” Int. J. Mach. Tools Manuf., vol. 123, pp. 146–159, Dec. 2017.

I need to take some pictures of powder particles with sizes of around 20 microns. I have an SC1 Edgertronic camera which can be found here. The location of the camera is shown in the above picture but the camera is actually connected to the side of the blade and is moving with it. Thus, the avalanches that the powder creates can be observed with the camera. An image of what I am referring to is shown below:

This is the Zoomed-in image of the above one (I know the fame # is different, but it is basically the same but at a different time).

As can be seen, the distance between the powder and the camera is large and the powder particles cannot be observed and tracked. I need a lens that is capable of getting the track of particles. As I mentioned earlier, this event is happening so fast, so I needed to use a high-speed camera like this. I do not need the features on the surface of powder particles; I only need to see how fast they are moving and what angle is the powder pile creating with the surface (the angle can be observed in the above picture).

Please answer the below questions:

1- Do you know whether I need a telephoto (zoom) lens or a macro lens? I have been searching the Internet for a while, but I 've got kind of confused. Sounds like the telephoto lenses would just get close to the subject while losing the focus; the macro lenses, however, would have a reproduction rate of at least 1:1, which would present a sharp image of small creatures. I have to mention the camera is only compatible with the F mount Nikon series lenses; so, is there any way I can convert other lenses to the F mount or somehow figure this limitation out?

I don't think that a zoom lens will give you the magnification that you need. I have a 100 to 400 F4L II Lens and at minimum focus it's just 1/3 life size. I think that 1x is the minimum mag you want to go for, and even that's a tough recommendation because I don't know the size of the blade that's pushing particles.

2- I think I need some kind of backlight illumination for these pictures to be able to see the particles in a way that they cannot be mixed up and be tracked pretty easily. Can you help me with the suggested backlight illumination for this project? Also, for backlight illumination, I need to have a light diffusion screen and non-flicker light source as well; what light diffusion screen is more recommended? What about the non-flicker lamp?

Looking at the stills I don't think that back lighting will help -it won't shine though that powder.

I think a high powered diffused LED light source would be best, especially if you're shooting video.

3- Do you know anyway or software that could count the time and place it on the pictures, just like the frame number, ISO, EXP time, and FPS as shown in the below picture?

No idea.

Since I need to have the particles in larger sizes on the camera's sensor, I was thinking I need a macro lens, but I was not sure. So I asked my question here to use the knowledge and experience of experts.

A macro lens and a crop factor sensor so that the particles will look larger in the video. So an APS-C camera (best image quality) or a micro 4/3 (larger subject size due to the bigger crop factor, lower image quality due to the smaller sensor).

I should mention I am new to photography.

Any help would be appreciated.

Thanks!

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rurikw
rurikw Veteran Member • Posts: 3,126
Re: Do I need a telephoto lens or a macro lens?

Thanks for the pictures, much clearer now what you need. A very special application and looks like you got the right special camera with sufficient frame rate. As I said in my earlier post in the open forum it's limited by its nesessarily low resolution (to achieve the high fps numbers) but since you say it's enough to have the patticles show as mere dots as the important thing is recording their path, it might be enough.

I'm afraid your case is way beyond the 'expertise' of somebody like me who uses his macro lens for the occasional flower shot. There are folks here who have experience with high speed macro photography who can help you better but I'll give my 2c anyway:

As you say, you'd benefit from more light. You are already close to the native monochrome ISO: 6400. Not sure if going color would help but that could give ISO 1600 according to the specs of your camera. Main thing is that with more light you could increase the shutter speed. 1/550 looks slow for fast moving particles.Since your camera is capable of 1/250 000 there's basically no limit to how much light you could use to increase your shutter speed though the speed of your particles determines what's enough.

You suggest back lighting. Could work to have the particles show as black specs against a white background. OTOH it looks like the particles are light colored so front light with dark backgtound could work too.

if the lens you already have gives you the right field of view and can focus on the subject I don't see that you could gain anything by changing it. But you need to consider the size of the particles in relation to the FoV to determine if you have enough resolution. If not, does your research allow you to shoot a narrower FoV, ie. show a smaller part of the scene or will that exclude crucial information? If so, could you use several cameras firing in unison at different parts of the scene and combine the frames aftetwards?

Good luck with your project.

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ThrillaMozilla Veteran Member • Posts: 5,031
Re: Do I need a telephoto lens or a macro lens?

It looks like you are taking 500 frames/second, which gives you 14 micron pixels. Thus, at 1:1 the image would be barely larger than one pixel. To resolve 20 micron particles you need far more magnification than the 1:1 that an ordinary photographic objective can give you unless you reverse the lens.

With correctly done darkfield lighting, particles can be seen at below resolution limits, but the brightness depends a great deal on the size. That would be sufficient to determine the location of a particle.

Besides lighting, you have four problems: resolution, depth of field, working distance, and field size. It is a special problem to get the magnification you need at the required working distance. The closer you can get to the subject, the better. Be aware that the depth of field may be extremely limited, so you may not be able to get the particles in focus. And it may be difficult to cover the whole field.

Canon makes an objective that magnifies up to 5:1. A photo objective can be reversed to get greater magnification, but resolution is the key. I don't know what kind of resolution you can obtain with these lenses under your conditions, because you didn't specify the required working distance. The working distance determines the numerical aperture, and therefore the smallest resolution.

It may be that you need specialized microscope objectives, or it may not be possible with conventional photomicrography. I think correctly done darkfield illumination may be the key--if it is possible. You need some special expertise for this project. In any case you need to provide more information.

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Guito55 Regular Member • Posts: 164
Re: Do I need a telephoto lens or a macro lens?

Have you investigated USB microscopes at all? I am think they may be a feasable option for you.

rankamaterur Regular Member • Posts: 332
Re: Do I need a telephoto lens or a macro lens?

You may need both.  That is, you may need "Macro" (Close focusing) and "Telephoto" (Longer focal length). It is not clear to me from your description how large a field of view you desire. If you were to put a graduated scale in the photo, how wide is the field? 2 cm? More? Less?

"Macro", as you correctly surmise, allows the lens to focus closer than a normal lens might. This allows you, of course, to make images of smaller objects, and still fill the frame. The problem with focusing very close with a macro lens is that the distance from the camera to the subject may become very small.

This is where a longer focal length "Telephoto" comes in. The longer focal length means that you may position the camera further from the subject, for the same size image (in macro usage).

There are some macro lenses with focal lengths up to 200mm or so, which might be helpful in your application. I'm not sure what focal length lens was used for your example photos.  I assume it is a "normal" lens of 50mm or so.

You are in luck that your camera takes an F-mount lens. There are many options for macro lenses, (or telephoto, for that matter) in Nikon F-mount. For video, you actually do not want the latest offerings from Nikon, because newer "G" lenses control the aperture from the camera body, and there is no aperture ring on the lens. I think this would be a problem for you. You need an older "AF-D" or even older manual focus "AIS" type lens. Once again, there are several macro choices in focal lengths from 55mm up to 200mm. I don't think autofocus helps you in your application.

If you find you need even more distance between camera and subject, you can experiment with non-macro telephoto lenses of 300mm focal length or more, but you would then probably need an extension tube, to achieve close focus. This is a whole different area, and beyond the scope of this note. There are many experts on this forum, however, who could help you with that, if that is the direction you need to go. If you were to do this, you would find that the camera rig would become quite large, as telephoto lenses tend to be bigger, and you might want an extension tube of 50mm or more.

Lighting for 500 FPS is another rather involved topic, and may become quite specialized for your application.

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