Pentax 67 on a Berlebach tripod Model 8043?

From the Tripod link:

Load capacity (kg) 8

From this random link about Pentax 67 lenses, the heaviest 165mm lens is:

SMC Pentax 67 165mm f/2.8 .. 0.835 kg

From Pentax 6×7 wiki, the camera:

weighing 2.3 kilograms (5.1 lb) with the plain prism and standard (105
mm f/2.4) lens

From the same lens link, the 105 f/2.4 lens weighs 0.59 kg, so your maximum camera + lens weight is: 2.3 – 0.59 + 0.835 = 2.545 kg. This is well within the load capacity of your tripod.

However the stability of the camera is also going to depend on the tripod head that you use. You will need to select a head with a suitable load capacity (and the weight of the head itself needs to be included in the total tripod load). While not absolutely necessary, a tripod head will allow you to easily aim the camera at your subject.

Finally I note that on that tripod link it says:

This product is no longer stocked and therefore cannot be purchased
until further notice.

So maybe you need another tripod selection????

machine learning – Which pretrained model will be best for my dataset?

I am trying to build a classification algorithm having 28 classes. These classes consists of Logo of companies like adidas , Nike etc. I have very low dataset below than 100 images and greater than 70 images. I have trained CNN model but not got decent results . Accuracy is not good. I want to switch on pretrained model. I don’t know which pretrained model should I use either VGG , ResNet etc. because I saw on Internet that you may use Pretrained model on similar dataset but I have logo of companies , I don’t know that any pre trained model is trained on such similar type of objects or not. How should I choose pre trained model that will performs well on my dataset.

Design an extensible permissions model in database

I’m trying to model a system with Users, Permissions and Products. The main goal is to have a way of checking if a User has a specific Permission in order to allow or deny other system operations.

So Users will have a list of Permissions and this Permissions will be given to the User when the User buys a specific Product.

This way the Users will have Permissions but the Products must have something like a “template” of the Permission that the User that buys the product will get.

This structure could be simplified to users having products and products having permissions but one of the requirements is to have the possibility of assigning a specific permission to a specific user without needing a product. And also each permission has its own context so, each permission has its own relation with a user and some other variables that mutate over time and can change the permission validity.

I’m trying to map this domain to a database structure but I’m stuck with the relation between permissions and products.


reverse engineering – How was this picture of a model on a boat with a sunset in the background created?

There’s a definite “HDR feel” to the photos, but I’m not sure if any actual HDR / exposure blending tricks have actually been used — it might just be strong curves and saturation adjustment, combined with odd lighting.

  • The photo has been taken against the light, but with the sun low in the sky and behind a layer of clouds, which will tend to diffuse the light and somewhat reduce the contrast difference between the foreground and the sky. I suspect that’s really the most important “trick” here.

  • The photographer may have used a polarizing filter to darken the sky and the reflected sunlight off the water. There may also have been a fill flash involved.

  • It’s pretty likely that the luminance curve has been adjusted to add contrast to the shadows (possibly using something like the Photoshop “Shadow / Highlight” tool, rather than by directly editing the curve), and the color saturation has obviously been increased.

    It’s possible that some of the adjustment may have been masked to affect only the foreground, but it’s hard to tell for sure. The images could also be exposure fused composites, with the sky and the foreground taken from separate bracketed images (or the same RAW image with different exposure corrections), but I actually suspect that, in this case, they’re not (see below).

  • Looking at the sky, especially in the second picture, you can tell that the highlights are pretty badly clipped, and it appears to be a sharp “digital clip” rather than a smooth “film clip”.

    I would consider this a flaw (even if it does add somewhat to the “dramatic” contrast), but it also suggests to me that the photos have probably not been processed too much (beyond the obvious contrast and saturation boosts) — or, alternatively, that whoever post-processed them wasn’t skilled enough to handle the highlights properly.

Anyway, here’s a quick example of how to post-process such images to bring out the foreground. The original image is a quick snapshot I took from a boat against the sunlight, with no fill flash, using a Nikon D70s at ISO 200, f/6.0, 1/8000 s. It lacks the dramatic sunset colors, but does illustrate the general issues with shooting against the light over water:

Step 1: Original image with no exposure correction
Step 2: Exposure boosted by +2.6 in ufraw
Step 3: Color saturation boosted to 170%
Step 4: Luminance curve adjusted to balance foreground and background
Top down, left to right: (1) original image with no exposure correction, (2) exposure boosted by +2.6 in ufraw, (3) color saturation boosted to 170%, (4) luminance curve adjusted to balance foreground and background.

Note how, without exposure correction, the foreground is severely underexposed. That’s actually deliberate; it’s a lot easier to boost exposure in post than to fix blown highlights.

All of this was done with global adjustments only; of course, with careful masking, much more would be possible. The tricky part here was getting the curve adjustment to look good. Here’s a screenshot of the curve I ended up using:

Screenshot of color curves in ufraw

You can see that there’s a strong contrast boost at the bottom end (corresponding to the subject in the foreground), with a compensating flat range in the “midtones” (which, here, basically means the constrast gap between the foreground and background) and a slight S-curve in the upper range corresponding to the highlights on the water (to give them a bit more contrast).

As for dramatic lighting, I’d say it comes mostly down to picking the right time and location. Here’s the kind of background you can get with a polarizing filter and the sun low behind clouds:

Sun behind clouds, taken with a cellphone camera through sunglasses

This is, in fact, a completely unedited photo taken with an old 0.3 Mpx cellphone camera, filtered through polarizing sunglasses. You can just imagine how awesome it would’ve looked if I’d had a proper camera with me. 🙂

identity – Entity Relationship Model

Draw an ER-Model for the following info that can appropriately record the info described :

Question : An Airport has a city name and International identification code (Eg: EDDH for Hamburg Airport). A fight is identified by its flight no (Eg: LH4324). A flight has a starting airport, a destination airport and a departure date. Further more, a fight has three prices (first, business, economy) and a status (not yet started, started, landed).

Can anyone on this forum solve this question for me. It will be grateful for me.

json – Can’t acces specific values in my node.js mongoose Model (only the Object)

I have been working at this for the past 4 hours. I would therefore like some help. I want to access the specific values in my database, eg. as although when adding imglink in console.log() I get undefined. I can get the general object but not the specifik values.

I have defined my Song Schema as:

const songSchema = new Schema({
    values: ({
    imglink: {
      type: String
    id: {
      type: String
    spotify: {
      type: String,
    soundCloud: {
      type: String,
    youtube: {
      type: String,
    appleMusic: {
      type: String,
}, {
    timestamps: true,

As you can see values is an array of objects. People with a similiar problem on here hadn’t included the correct values in their Schema, so maybe that’s my problem? Although to me it looks correct. I then GET the values in my database. The JSON object usually looks something like this:

    "_id": "5ffbba4dc47e847a79c9c68f",
    "values": (
        "_id": "5ffbba4dc47e847a79c9c690",
        "imglink": "imagelink",
        "id": "id",
        "soundCloud": "soundcloudvalue",
        "youtube": "youtubevalue",
        "appleMusic": "applemusicvalue",
        "spotify": "spotifyvalue"

I call it by this function, which is supposed to print out the individual values:

      const getAllSongs = () => {
    .then(function (response) {
      console.log(response); // returns an object
      console.log(; // returns an object  
    .catch(function (error) {
        // handle error

I have an Express route object that allows me to access a song by it’s id as GET http://localhost:5000/songs/id in the VS-code HTTP client (similiar to postman):

    router.get(`/:id`, function(req, res) {
    return Song.find(
    ).then(function(song) { 
        // return orders when resolved
        res.json('works yesss');
    .catch(function (err) {
        // handle error
        res.status(400).json('Error: '+err)

Here are some popular solutions I have tried:

Wrapping response in JSON.stringify() doesn’t work.

toObject() and toJSON() don’t work either as they aren’t defined when I use them.
the _doc hack doesn’t work either.

I have tried looking at the Schema which is where I think the problem is. The POST-request adds the right data, the GET-request goes through I just can’t acces the specific values.

I hope you have the time to help, thanks. I will be extremely grateful. And of course let me know if you have any questions.

security – Am I really understanding how the “Trezor Model T”, and hardware wallets in general, work?

Getting increasingly paranoid about losing my coins, I’ve yet again (for probably the 20th time by now) went looking for hardware wallets. The only semi-reasonable one seems to be the two Trezors. All the others seem fishy/unreliable to me.

But as I read and watch and listen, it seems like even the “premium” Trezor Model T requires “OS support” and even to go to a webpage (not hosted on the device itself) to actually use it. Its operations are not at all self-contained in the device itself.

Up until now, I always had the idea that the Trezors (even the first model) is entirely self-contained, and only plugs into a computer in order to use its network capabilities to be able to send coins and update its data. (Of course, doing all the validations and verifications on the device, so it doesn’t have to trust the network or the computer it’s plugged in to.)

Actually, I vaguely had the idea that I would be able to buy one and then physically take it with me somewhere, without any computer around, and sort of “beam” any amount of my coins into another person’s Trezor or even other hardware wallet…

None of this seems to be the case. Even the expensive model with the touch screen appears to be entirely reliant on the “host computer” to do anything besides storing the coins. I bet the special Trezor “coin control panel” webpage doesn’t even support my browser (I don’t run spyware), and who knows how long that will stay online? I don’t want to rely on some company’s website, or require special “OS support” for my hardware wallet. That’s why it’s a hardware wallet! For it to be stand-alone.

Am I missing something fundamental? Are there no “actual” hardware Bitcoin wallets which can do everything by themselves: send and receive coins without any computer? I don’t even have wireless Internet at home, but most people apparently have, so I definitely expected it to be using “wifi” on its own, but this doesn’t seem to be the case?!

I really tried to find this out by myself before asking.

One-to-many relationship in django models (Relation of one Model with another two Models)

I want to save all the likes in a Like Table.

Likes of both Comments and Post, in one table.

Is their something like this to achieve this thing:

Class Post:

Class Comment:

Class Like(models.Model):
   '''Either of Post or Comment will have to be selected in this field'''
   post_or_comment = models.Something((Post, Comment), on_delete=models.CASCADE)