Author Topic: Which thermal camera for monitoring my Raynaud's & my body heat? P2Pro,T2S,T3S?  (Read 3912 times)

0 Members and 1 Guest are viewing this topic.

Offline Jet1Topic starter

  • Contributor
  • Posts: 14
  • Country: se
Hi,
I have Raynaud's Phenomenon (poor circulation condition) and want to buy a thermal camera for monitoring how heat moves in my body after exposing myself to what triggers the condition (such as cold exposure of various kinds), this way finding areas of especially weak blood circulation for example.

My budget isn't high, just a couple hundred dollars. I'm currently looking at the P2 Pro, the T2S and T2L from InfiRay. I don't quite understand the difference between them. What I do understand however, is that those would be good for diagnosing electronics, but I don't know if they would be as good for monitoring how heat moves in a human body and human body temperature measurement. The T3S from InfiRay seems to be a little more geared on the company's Alibaba page towards medical care, more so than any of the P2Pro, T2S or T2L. So maybe a T3S is needed to monitor my Raynaud's properly, though this model is above my budget currently.

I don't really care about the size of the camera, but I would like to purchase one that I would be able to connect to my Android phone and use on my PC with a software (such as the Windows software for some InfiRay cameras created by Rune Hansen on this forum).
Based on my preferences, which thermal camera would you recommend for me?

Thanks in advance for your help!
 

Offline Vipitis

  • Frequent Contributor
  • **
  • Posts: 867
  • Country: de
  • aspiring thermal photography enthusiast
I would not trust any of these devices to provide accurate temperature measurements. Will you see heat change and move? Maybe.

It sounds more like you need a professional medical assessment, which will likely use a cooled mwir camera. These are able to imaging much finer temperature deltas and when calibrated, provide actual numbers of the surface temperature.

 
The following users thanked this post: Jet1

Offline Jet1Topic starter

  • Contributor
  • Posts: 14
  • Country: se
Vipitis, thanks for the reply I appreciate it. I would love to get a cooled mwir camera, but I have understood that they are very expensive and I couldn't afford paying several thousands dollars - or have I misunderstood and is there cheaper cooled mwir cameras available to purchase?

Otherwise I would have to settle for a non-cooled camera, even though it wouldn't be quite perfect for my uses. I'm just a layman trying to get some basic understanding of how heat moves in my body and I doesn't work in conjunction with a doctor. Is there a thermal camera within my budget of a couple hundred dollars which would work reasonably well for my uses? (I'm considering InfiRay's line of the P2 Pro, T2S+ or T2L as I've understood that that they are decently priced for their capabilities, but there might be other better priced cameras I'm not aware of)

Thanks again for the help!
 

Offline aargee

  • Frequent Contributor
  • **
  • Posts: 877
  • Country: au
Jet1,

I can't see a problem with the P2 Pro, I have one on order and also currently have a Flir E4.
It sounds like you're after indicative measurements rather than accuracy and these smaller, cheaper sensors should fit the bill in that area.
If you haven't already, see Mike's P2 Pro review here , that should give you a good indication of what to expect.
Not easy, not hard, just need to be incentivised.
 
The following users thanked this post: Jet1

Offline Fraser

  • Super Contributor
  • ***
  • Posts: 13263
  • Country: gb
I reviewed the Infiray P2 Pro on this forum here:

https://www.eevblog.com/forum/thermal-imaging/review-infiray-p2-pro-thermal-camera-dongle-for-android-mobile-phones/25/

Post numbers 36 and 45 may be of some interest as they image hands. My wifes warm blood in her veins was visible in post 45.

The P2 series does not officially have a PC image analysis software package but I recall someone on this forum has created such software that runs under Python. I cannot say whether the P2 series will meet the OP's needs as medical thermography is quite a specialist use case and I am not a Doctor.

Fraser
« Last Edit: January 25, 2023, 09:07:36 am by Fraser »
If I have helped you please consider a donation : https://gofund.me/c86b0a2c
 
The following users thanked this post: Jet1

Offline Jet1Topic starter

  • Contributor
  • Posts: 14
  • Country: se
aargee, thanks for the reply and the video link. It's an interesting video and I especially like the showcase of the function to add temperature measurements by drawing lines in the phone app. You're right that I'm more after indicative measurements - spot-on accuracy isn't really needed - I just want to get an visual understanding for how heat moves in particular parts of my body and identify weak points.
You mentioned that you currently have a Flir E4. Why did you decide to order a P2 Pro as well? Does the P2 Pro have better capabilities than the E4 (even though the E4 seems to cost quite a bit more than the P2 Pro) ?

Fraser, thanks also for your reply and for your in-depth and well-made review of the P2 Pro. Those images you've posted of hands and how warm blood is visible in the veins is exactly the kind of detail I'm looking for in a thermal camera. The P2 Pro seems to be able to offer a lot of what I'm looking for, now I'm just only pondering if I should go for this particular model or another model from Infiray.
After reading some of your previous posts I've understood (please correct me if I'm wrong) that the P2 Pro use the Tiny1 core, whereas the T2 series (like T2S plus and T2 Pro) uses the larger S0 core. What I'm wondering then, is that if I don't care about the smaller size and just want to get the most capable core with the highest features, would it in that case be better to buy a camera with the S0 core rather than the smaller Tiny1 core? Or is the Tiny1 core just as strong and feature packed as the S0 but just a newer smaller version of it?
 

Offline Fraser

  • Super Contributor
  • ***
  • Posts: 13263
  • Country: gb
OK, I have resisted saying too much on this topic as it is not in my realm of experience. I can, however, provide some insight into the use of one of my better thermal cameras that was sold to a Doctor who specialises in thermography of the human body. He claims to be able to identify all manner of illnesses through the use of detailed thermography in association with bespoke image analysis software written especially for him by a company in Germany. The Doctor needed my NEC AVIO TH7302W static "Box" camera as the analysis software was written for it. That camera falls into the "professional" category with excellent imaging, measurement accuracy and flatness of field. The Doctor suggested these aspects were essential for medical imaging of the human body. The camera was also manual focus and this permits a nice sharp image of the test subject for optimum image quality.

Now some thoughts on thermography of the human body.....

To evaluate the skin temperature the test subject must not have any clothing covering the region of interest and should be in a room with an ambient temperature that does not trigger a response form the body that draws its thermal energy into its core organs and away from the skin. The skin is a very large organ and part of the bodies thermal regulation process. As such the surface temperature of skin can vary greatly depending upon many variables including ambient room temperature, draughts, stress, illness and blood alcohol level. When carrying out thermography of the human body you only see the surface in terms of detail. Veins stand out because they are just below the surface and warmer than the surrounding flesh and skin. A thermal camera does not provide detailed insight into the bodies blood circulatory system where it is located deeper in the flesh. It is possible to image the inadequate circulation to body extremities such as hands, fingers, feet and toes but detailed imaging the point of circulation constriction is unlikely to be possible.  In general the human body will present itself as a surface that varies a few degrees in temperature depending upon how close to the surface blood is flowing. Classically a human loses heat through their head and thighs and these will show hotter than the abdomen. The hands/fingers and feet/toes will often show cooler as they are extremities of blood circulation.  From what I understand Reynauds disease effects the circulation and so temperature of the hands and feet. This should be clearly visible on most thermal imaging cameras as the effect is pronounced in many cases.
Sadly images of other parts of the human body may provide far less obvious changes in temperature, if indeed Reynauds effects them as well. The blood flow is deeper under the surface and sometimes the fatty layers preclude detailed imaging. It is when examining these more challenging areas of the body that a thermal camera with good imaging and measurement performance is needed. In medical imaging it is not uncommon to use cooled MWIR thermal cameras as these offer great sensitivity and very low noise imaging. An uncooled microbolometer based thermal imaging camera can still provide some useful imaging but it is more limited in terms of sensitivity and image noise content that can interfere with the diagnostic process.

I would advise against spending large sums of money on a professional thermal camera setup as much of the diagnostic process relies upon image interpretation by those with significant experience in body thermography and illnesses that may be detected and profiled by such technology. For general interest in your bodies thermal profile and behaviour to various stimuli, any of the modern budget thermal cameras on the market can provide basic imagery. Infiray, Hikvision, Guide Sensmart and UNI_T all offer budget cameras with resolution just under QVGA (256 x 192 pixels). At close range the imaging will show warmer and cooler areas of the body, but little detail in the thorax region. I personally recommend a camera that provides manual focus to enable the sharpest possible imaging of your skin at various distances. Fixed focus cameras do work but are a compromise solution with less than optimum focus at most distances. Image analysis software on a PC is very useful for post image collection analysis and measurement. Carrying out image analysis on a camera or phone is far from ideal due to the small display size.

I do not know what you hope to achieve with the thermal imaging that you collect of your body but I wish you well with the exercise and hope it helps you. You may wish to talk to you doctor about the idea and please be careful if self-diagnosing without the training and experience of a specialist Doctor.

With all that said, thermography of the human body can be great fun. If you image a person before and after they have been in cold water, you see how the human body tries to cope with the 'threat' to its core temperature. Arms and legs become cold as blood is diverted to keep the core at operating temperature. In a runner you can see the work that certain muscles are doing and when out in cold weather the benefit of wearing a warm hat may be clearly seen :-+ The human bodies thermo-regulation system is very clever indeed and responds to perceived threats to the core temperature quickly as otherwise Hyperthermia kicks in and the body fails.

One thing people keep asking me is whether a thermal camera can measure a human body core temperature. The simple answer is NO, not directly. Core temperature may be estimated or predicted using well studied regions of interest such as in the corner of the eye, nearest the nose, Temporal Artery and inside the ear canal. Those temperatures reflect core temperature because of good blood flow from the core. If core body temperature drops very much, you begin to die ! Core temperature should remain within quite tight limits if you are healthy.

All good fun

Fraser 
« Last Edit: January 27, 2023, 08:29:56 am by Fraser »
If I have helped you please consider a donation : https://gofund.me/c86b0a2c
 
The following users thanked this post: Jet1

Offline Jet1Topic starter

  • Contributor
  • Posts: 14
  • Country: se
Fraser, thanks so much for taking your time and providing such a comprehensive reply. That is exactly the kind of information I'm after in order to decide which thermal camera to purchase. You actually seem to be spot-on with how I reason for making my purchase, as - just how you write -  I've come to understand that a professional thermal camera setup is way above my budget and interpreting the results would be above my level of expertise anyway, so what I'm looking for is just the best camera within my budget - I'm really just looking to play around with the camera and hopefully get some understanding of my Raynaud's in the process. I'm not doing this in a medical setting or in collaboration with a doctor, so don't feel like I'm looking for medical advice :) Just looking for some opinions - so please don't feel like you need to hold back with what you know just because it's not within your realm of experience, though based on your reply, you seem to have a whole lot of useful knowledge in this field and I'm grateful for you sharing it  8)

Now what I also gather from your reply is that for my purposes - and to get a somewhat decent result - I should get a camera with manual focus (which I suppose excludes the P2 Pro which is a fixed focus lens) and as close a resolution to 512x192 pixels as possible. I'm not familiar with the makers Hikvision, Guide Sensmart and UNI_T you mention. So far, I've only been reading up on InFiray's offerings and I suppose T2S, T2L or T2 Pro would be best suitable for my budget and what I'm looking for. Please feel free to suggest some alternatives which might be better.

It's interesting how you mention that to evaluate skin temperature the subject should be in a room with a temperature that does not trigger it's response to draw thermal energy away from the skin and into its core organs. I'm actually doing a lot of ice bathing in order to train my body to become better at handling that response which draws thermal energy into the core organs. The thing I've realized with Raynaud's Phenomenon is that it often occurs because the body reacts too intensely to a trigger, and by doing ice baths my body has actually become better at handling various triggers. Some years before I could get white hands (a symptom of Raynaud's) right in the middle of the warm Swedish summertime just by eating some cold yoghurt, but nowadays my hands only get white after a long cold exposure such as ice bathing and really cold showers.
One of the reasons I've begun to look at purchasing a thermal camera is because I would like to see in infrared how my body reacts when getting into ice cold water (but also how the heat moves in my body afterwards right before the onset of white fingers and toes). So I suppose that the camera I'm looking for should be able to be used outside (no need for waterproof though, since I would keep it above water) and that might exclude the T2S+ and T2L as they're described by InfiRay as indoors cameras. That leaves the T2 Pro, but I don't know if it's level of temperature measurement (not of the body core temperature, just the surface) and how heat moves would be as detailed as the T2S+ and T2L which are described as macro temperature measurement devices (actually they're described by InFiray as "king of macro temperature measurement" :)) Argh, its really a jungle trying to understand the different models and finding the perfect one within my budget  ;)
 

Offline Fraser

  • Super Contributor
  • ***
  • Posts: 13263
  • Country: gb
Jet1,

Apologies a typo crept into my previous message. The resolution should have read as 256 x 192 pixels which is just under QVGA. I believe that resolution will match your needs and budget well. Regarding the "indoor" comment against the T2 series, that relates to their weatherproof rating and is not a limitation on where they may be used. Just do not use it in heavy rain or in water ! The "Macro" function is related to the minimum focus distance of the lens. Many manual focus wide angle lens equipped thermal cameras have a minimum focus distance of around 30cm. Infiray are chasing the PCB analysis market so created a camera that could focus close to a PCB to image modern miniature SMD components. The Macro function would only matter you toy if you desired imagery of, for example, your finger tips and skin pores.

From what you have said, the Infiray T2 series of cameras appear to provide what you need on a limited budget. You will also need a decent mobile phone as the Host though. I have tested the Samsung Galaxy A6, A8 and S9 phones with these cameras and they performed very well together. A Phablet or Tablet might be a better option if image analysis is needed as the increased display size helps with such activities. I believe that there is PC software written by a fellow forum member that supports the T2 series as well. If the budget can stretch to it, a T3 series camera would be the next step up from a T2 series. Other brands of phone dongle are available but, personally, I have found the Infiray products to be excellent value for money.

Fraser
« Last Edit: January 27, 2023, 02:56:27 pm by Fraser »
If I have helped you please consider a donation : https://gofund.me/c86b0a2c
 
The following users thanked this post: Jet1

Offline Jet1Topic starter

  • Contributor
  • Posts: 14
  • Country: se
Fraser, thanks again for a good and informative reply.
I see, so the reason that the models T2S Plus and T2L are marketed as "indoors" have more to do that their casing isn't weatherproof and they could still be used outside. That would probably mean that the T2 Pro is weatherproof (though not waterproof) since it is marketed as outdoors. That's some useful information as I'm trying to figure out the main differences between the models of the T2 series. From what I'm reading on InFiray Alibaba descriptions I would then like to draw a simplified conclusion that the main difference between T2 Pro and the two others is that the T2 Pro has a weatherproof casing and a lens more optimized for zooming longer distances (marketed mainly for hunting). Whereas the T2S Plus and T2L have lenses that are better at getting detail at close up distances (marketed mainly for electronics). Now the difference between the T2S Plus and T2L seems to be harder to distinguish, I can't seem to interpret any major difference apart from the T2S Plus being able to handle a wider span of temperature range (T2S PLus: -20~450C compared to T2L: -20~120C) and having a slightly better temperature accuracy. Though their casing looks a little different and the T2L looks a little more like the casing of the T2 Pro, so maybe the T2L is something of a hybrid between the T2S Plus and the T2 Pro. I don't know :-// At least I suppose that all three of them use the same technology on the inside (the S0 core) and the main difference then being the casing and lens used - or maybe I'm wrong and the S0 core isn't the only core being used for the T2 series.
Though as you write, any of the T2 series appear to provide what I need on my limited budget - so maybe I should just pick up the one of them that I could find at the cheapest price (I'd love to pick up something from the T3 series, but they seem to be at least double the price as the T2 series, so unless the T3 series wouldn't offer any spectacular gains warranting paying double the price and breaking my budget, I would have to stick to the T2 series).

Thanks also for the advice on what mobile phone to use in conjunction with the T2 series. I'll probably purchase a pre-owned A6, A8 or S9 and use it exclusively for the thermal camera when doing outdoor measurements. Nonetheless I'll mostly use the thermal camera inside and then I'll definitely use it in conjunction with a PC software on my laptop for better image analysis. I think I'd use RuneHansen's software, I guess that's the one you're referring to as well.

Thanks again for your help, it's greatly appreciated.
 

Offline Fraser

  • Super Contributor
  • ***
  • Posts: 13263
  • Country: gb
The Infiray Tiny1 and S0 cores may be configured with a more restricted measurement range (-20C~120C) or the fully capability of the core (-20C~450C). Infiray sell cameras that use these cores with either the 'restricted' measurement range or the full capability. It allows them to market the units at different price points. The hardware remains the same, it is the configuration of the firmware that releases the full measurement potential of the core.

With the T2 series of cameras, Infiray has attempted to offer models that meet the needs of a range of potential customers. They offer the 'Generic use' basic model and enhanced models that offer greater measurement temperature range and/or different optics. The T2 Pro is intended to be used by those wishing to observe more distant targets so the FOV of the lens is smaller. The specification of each camera model tells you the story of what the model can do and whether it is suited to your particular use case. The T2 series all use the same S0 imaging core.

Fraser 
« Last Edit: January 28, 2023, 08:46:50 am by Fraser »
If I have helped you please consider a donation : https://gofund.me/c86b0a2c
 
The following users thanked this post: Jet1

Offline Jet1Topic starter

  • Contributor
  • Posts: 14
  • Country: se
Fraser, thanks again for a great reply.
I've totally overlooked the field of view (FOV) when comparing the models, thanks for pointing it out. This might actually mean that some models might not be suitable for part of the things I'm intending to use them for, since when doing outdoor measurements of how my body reacts to cold stimulus I would need to capture my whole body in the field of view. For this I'd intend to place the thermal camera on a selfie-stick (with the attached mobile phone) between 60 to 90 centimeters away from my body, so the thermal camera would need to have a broad enough field of view to include my whole body (I'm of normal height) in the view. I guess this might exclude at least the T2 Pro since in InFiray's Alibaba description the FOV is only stated as 13.6x10.2 degrees, so from 60-90 cm away it might not be enough of distance to capture my whole body in the view. I'm not so familiar with estimating the field of view so I don't know if I would be correct in this assessment. Though I think (but could be wrong) that the T2S+ and T2L with their FOV of 44.9x33.4 degrees would be able to capture my whole body from 60 to 90 centimeters away, but then I've come to think of that maybe the clarity of image wouldn't be so clear from 60-90 centimeters away and that the infrared image would be quite blurry from these distances as the T2S+ and T2L might not be supposed to be used at 60-90 centimeters away but more closer to what is being measured  :-//
What do you think about this?

Thanks once again!
 

Offline Fraser

  • Super Contributor
  • ***
  • Posts: 13263
  • Country: gb
60cm to 90cm distance is well within the capabilities of the T2L and T2S+ They focus from quite close distances of, say 30cm, out to infinity. Capturing your whole body at a range of only 90cm is asking too much of these cameras though. That would end a very wide angle lens and even if you had such, the image detail would suffer as the pixels are spread over a very large field of view. To image a nominal height humans full body the camera will need to be a few metres away.

Fraser
If I have helped you please consider a donation : https://gofund.me/c86b0a2c
 
The following users thanked this post: Jet1

Offline Fraser

  • Super Contributor
  • ***
  • Posts: 13263
  • Country: gb
I just looked at the distance you would need to view a nominal 1.8m high person using a 45 Degree field of view lens. You will need to position the camera approximately 2.5m from the person and use it in the ‘portrait’ orientation.

For your desired ~1m viewing distance you would need a 90 degree HFOV lens.

Please note that with increasing distance to target or increased field of view at a set distance, the penalty is loss of thermal detail as the pixel size on the target increases. Even 45 Degrees HFOV is quite large when it comes to IFOV and it’s effect on image detail at increased distances from the target. Just look at the loss of fine detail in the images of buildings that I included in my P2 Pro review and the image detail at set distance test I carried out with a test mask on my thermal black body. You have a very limited number of pixels, use them well.

Fraser
« Last Edit: January 29, 2023, 11:14:00 am by Fraser »
If I have helped you please consider a donation : https://gofund.me/c86b0a2c
 
The following users thanked this post: Jet1

Offline Jet1Topic starter

  • Contributor
  • Posts: 14
  • Country: se
Fraser, thanks again for a useful reply and for checking the distance needed for me.
I'm actually below 1.70m in height, but I don't suppose that would make that much of a difference for the FOV needed :) The farthest away I could get the camera while attached to a selfie-stick would be 90 centimeters, so it would be quite below the needed 2.5m. I suspect that a 90 degree HFOV lens would be way above my budget. What is the cheapest thermal camera with such a 90 lens (either built in or as an addon accessory) you know of?

Thanks once again!
 

Offline aargee

  • Frequent Contributor
  • **
  • Posts: 877
  • Country: au

You mentioned that you currently have a Flir E4. Why did you decide to order a P2 Pro as well? Does the P2 Pro have better capabilities than the E4 (even though the E4 seems to cost quite a bit more than the P2 Pro) ?


Yes, it the P2 has certain better capabilities.
Not easy, not hard, just need to be incentivised.
 
The following users thanked this post: Jet1

Offline Jet1Topic starter

  • Contributor
  • Posts: 14
  • Country: se
aargee, thanks. May I ask in which ways it has better capabilities?

As a follow-up to my previous post in reply to Fraser's useful reply with what FOV is needed at which distances: I've come to think about that instead of relying on a selfie-stick, in this case it would be better if I just placed the camera on a static tripod and then positioned myself a few meters away to be in full view in a 45 degree lens. Hopefully the image detail would be decent enough and not so much thermal data being lost that the image would be unusable. At least this way it would work with the lens of either a T2S+ or T2L.
« Last Edit: February 01, 2023, 12:48:45 am by Jet1 »
 

Offline Fraser

  • Super Contributor
  • ***
  • Posts: 13263
  • Country: gb
 :-+
If I have helped you please consider a donation : https://gofund.me/c86b0a2c
 
The following users thanked this post: Jet1

Offline Bill W

  • Super Contributor
  • ***
  • Posts: 1107
  • Country: gb
    • Fire TICS
Hi,
I have Raynaud's Phenomenon (poor circulation condition) and want to buy a thermal camera for monitoring how heat moves in my body after exposing myself to what triggers the condition (such as cold exposure of various kinds), this way finding areas of especially weak blood circulation for example.

One of my former colleagues had Raynaulds, although just in one finger.  That was clearly visible in any of our fire cameras (320x240) as he used it as his factory visitor 'tourist trail ' party trick.

His finger was basically at ambient - so not looking for small differences.

Bill
 
The following users thanked this post: Jet1

Offline Lambda

  • Regular Contributor
  • *
  • Posts: 126
  • Country: nl
Hi.  :)

I dare to shortly come in this thread, just for bringing an additional illustration about what said Bill here:


One of my former colleagues had Raynaulds, although just in one finger.  That was clearly visible in any of our fire cameras (320x240) as he used it as his factory visitor 'tourist trail ' party trick.

His finger was basically at ambient - so not looking for small differences.

Bill

In this video i just made, one of the most common symptom of the Raynaud syndrome is clearly visible through the hand monitoring. The camera used is based on an ancient core and has moderate performances compared to modern standards.



I hope Jet1 you will, as soon as possible, implement your project. With the above collection of advices and analysis, you have already plenty of priceless information for that.  :-+
On top of everything elsel, i hope you will get rid of this syndrome, form one way to another.

Good luck.

Stéphane
« Last Edit: February 06, 2023, 09:53:31 am by Lambda »
 
The following users thanked this post: Jet1

Offline Jet1Topic starter

  • Contributor
  • Posts: 14
  • Country: se
Bill, thanks for the input. It's strange how Raynaud's manifests itself. Although I don't have it in just one of my fingers as your former colleague, I've found that sometimes one particular finger acts up more than the rest and then the next time it could be another finger. It's a little like one finger get's slightly more affected by the cold at one time and then the body factors in that the next time so that finger doesn't get as affected the next time. I'm still trying to work out how this works and that's one of the reasons I'm now purchasing a thermal camera.

Stéphane, thanks also for your input and the video. I suppose my fingers will look like the one with Raynaud's in your video and I will test it out in different circumstances to measure the changes. I hope to learn how different levels of cold will affect the hands and in what way I could myself influence my reaction. Based on my training in pretty severe cold exposure I've come to realize that there is definitely a connection between the way Raynaud's manifests itself and how much cold my body can handle - the more accustomed my body get to cold exposure, the better my Raynaud's gets. I don't know if this solely depends on my body getting better at distributing heat in my body the more I train, or if it has more to do with me getting better at handling the mental stress of cold exposure (since Raynaud's also has a lot do with stress according to what I've read). Nonetheless I'm confident that I'll one way or another get rid of this syndrome.

I've now taken the step to order a T2S+ and look forward to trying it out on my body  :)
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf