NMGPhotos

On 1/21/2023 at 5:04 AM, rodeo_joe1 said:

Starting with that basic formula and a bit of trigonometry, you can work out the out-of-focus light cone intersection with the image-plane and calculate the corresponding subject distances for near and far limits of focus. Easy! (Not) 🤔

I'm pretty good with math, lol! do you know of any comprehensive guides (perhaps maybe with visuals) that show how this works?

12 hours ago, rodeo_joe1 said:

according to my depth-of-field spreadsheet, the D-o-F of a 5mm lens at f/1.7 is about 18m with a 4m focus;

What is the 4mm focus in reference to, and also how is D-o-F calculated like this?

15 hours ago, AJG said:

27 mm equivalent focal length is probably something more like 4 or 5 mm actual focal length or even less.

What are you basing this calculation on? Just curious.

15 hours ago, AJG said:

With a focal length that short you could still have enough depth of field for the grate to be in focus even though you have focused on a distant scene behind it.

It was my understanding that the f-number has effect on DOF, but can focal length have effect as well?

15 hours ago, AJG said:

As great as phone cameras can be, if you want control of the final image you are better off starting with a more sophisticated camera that allows full manual operation of focus, exposure, etc.

Completely understand and completely agree. Was just curious about the differences.

23 minutes ago, Ken Katz said:

Frankly, using almost any camera and lens, such a dense grate would likely be visible in the image, even if you manually focused on the objects beyond the grate.

That is interesting. Looking through the viewfinder, I was unable to see the grate. I don't know if it would have shown up on film as I didn't have any at the time.

I am still curious as to why my phone camera was unable to focus past the grate (even when focused manually). Not that I expect it to, just wondering about possible reasons.

6 hours ago, AJG said:

You mentioned that your phone camera lens was f/1.7.  Did the specs say what the focal length was?

Looking at specs it appears to be 27mm (full-frame equivalent). This does still seem a bit strange, as a shallow depth of field should let me focus past the grate? I would assume it's perhaps the size of the lens in relation to the size of the holes.

18 hours ago, Gary Naka said:

Post a picture of the grating.
That would make evaluation a LOT easier than guessing what it looks like.

Apologies! Attached is a picture I took with my phone camera. As mentioned, my SLR lens could easily focus past it and to the bus behind it.

1 hour ago, AJG said:

Almost all film SLRs can be focused manually, so you get to choose what is in focus rather than the AI on a chip in your phone.

I understand that. Just for your information though, I did try using a manual focusing app and even focused as far as the app would let me and the grate was still was clearly visible. Again, not particularly surprising, just wanted to add that.

1 hour ago, AJG said:

 The other aspect is that phone cameras have very short focal length lenses in comparison with a 35 mm SLR's normal 50 mm lens and the shorter the focal length the more depth of field you will have, which means that objects close to the camera and those far away can be in focus at the same time. That 50 mm lens will probably have a wide open f/stop like f1.8 or f/1.4 which has very little depth of field when used at its widest opening.

According to spec sheets, the lens on my phone is a fixed ~f/1.7 (which is surprising, as that should lead to a very shallow depth of field?). Could the size of the lens also play a factor?

1 hour ago, AJG said:

This means that when you focus on the scene far behind the grate that the grate itself will be so far out of focus that it all but disappears in the picture.

If it's (at least partially) solid, why would it disappear instead of obstructing the view? At what point does a grate become an obstruction you can't focus past?
 

1 hour ago, AJG said:

You would notice the the grate did cause some softness in a print if you got that far, and if you photographed a similar scene without a grate near the camera to interfere that it will be sharper.

Thanks for this info! That does make sense.

31 minutes ago, alan_marcus2 said:

Tempted to say this is diffraction (path of light rays moving around an obstacle).

That does sound like a plausible explanation.

32 minutes ago, alan_marcus2 said:

More likely: The circular holes you are shooting through are likely acting as a diaphragm. The iris can be forward of the lens or behind or between the lens elements. Think about the tiny aperture opening of the camera lens and the fact that despite its tiny diameter a complete image is realized. 

That is also very interesting. They are small-ish holes. I still just find it fascinating that it's able to disappear like that.

I recently got a film SLR and was playing around with it at the bus stop earlier today. The bus stops shelters where I'm at have, on one side, a coarse grate-like design with circular holes. There is a lot of material between the holes. However, the lens I had was able to focus past it and onto the objects behind it very easily to the point where, at least through the viewfinder, you wouldn't be able to tell it was even there. Granted, it was late at night and perhaps objects beyond it being lit more helped, but I am curious as to the physics of this.

My phone camera was not able to focus past it (although I didn't expect it to be able to).

I may take a look! I've actually gotten two more cameras in the meantime, lol!

21 minutes ago, AJG said:

My guess would be that it was dropped on the diaphragm actuating lever and it bent.  Don't be too surprised if it isn't optically fantastic,

Sounds interesting. And yeah, I don't expect much. But thanks for the help 🙂

Ok, no now I see what you're saying @AJG. It is likely the lever mechanism. But I am not sure why it is different on the Quantaray. Is an adapter needed? Or is it just a crappy lens?

EDIT: Perhaps it is bent. If it is, that's impressive because it's pretty solid.

EDIT 2: Use some pliers to bend it back upwards. Seems to have fixed it? No idea how it got bent in the first place.

10 minutes ago, AJG said:

If the bent one is the problem lens that gets dimmer as you select a smaller f/stop then the bent pin probably isn't coming in contact with the lever in the camera that causes the lens to stop down from maximum aperture when you press the shutter.  If all of these lenses cause the finder to get darker when you stop down then there is probably an issue with the diaphragm mechanism in the camera body.  K mount lenses stop down when the lever in the camera body moves to one side and the lens stops down with a spring loaded mechanism built in to each lens.  They open back up when the lever in the camera body returns to its original position after the shutter closes.  Some older Ricoh K mount lenses don't play well with Pentax bodies although usually the problem is that you can't remove them from the Pentax body when you want to. 

The "bent" one is the only one in which the view through the viewfinder is dramatically changed when adjusting the aperture. The others show little to no change. I thought I noticed some change on one, but on repeat tests, I saw no change.

I also put "bent" in quotation marks because it seems to be how it was designed. The material does not appear weaker at the curve (which would be more likely if it was actually bent from its proper position).

As for the levers, I can move them on the lenses themselves, but when they are attached and I press the shutter, I see no movement on the aperture.

Additionally, to be specific, it's the Quantaray lens that does not work.

Also, I was wrong about the other lenses not changing apparent brightness when the aperture is adjusted. It just seemed more dramatic on that one lens for some reason.

EDIT: No, I was right. It's basically no change on the others.

Attached are photos of the difference lens (front, rear, and latch).

@tony_parsons1

2 hours ago, John Seaman said:

The K1000 only needs a battery for the exposure meter. Otherwise it's completely mechanical and will work without a battery. The troublesome lens seems to have an issue with the aperture. It should have a small lever on the rear which opens and closes the aperture - that's the set of blades in the lens which open and close to control the amount of light passing through. This lever should move freely. If it's stuck it could be affecting the mechanism of the camera.

Yeah, I assumed as much, but a battery doesn't hurt! As for the lever, it does indeed move freely, but the lever mechanism itself is shaped slightly differently than the others. That may be the difference here. Photos incoming!

Will do soon! I went out to buy a battery for the camera's light meter. I'm also wondering if that may be the reason it doesn't work.

Another interesting thing: for the lens that doesn't work, adjusting the aperture actually causes the view through the viewfinder to dim or brighten. The apparent brightness doesn't change with the other lenses.

I bought a Pentax K1000 and three lenses that fit on it at my local flea market. Two of them work nicely but the third causes the mirror to stick in the upwards position. Removing the lens and firing the shutter helps the mirror come back down.

Looking on the back (the mounting side), it appears ever so slightly different than the other two lenses, but not in any way which I would think would cause this. Is this just an incompatible lens or some other issue?

20 hours ago, rodeo_joe1 said:

Yes. There's no difference between the 'leader' and any other part of the film. 

Nice! Thanks for the confirmation 🙂

Just shot a roll over the past few days and hopefully it all turned out fine! Lost the button to allow for reverse, but it just threaded onto a push-stick anyway, so I could just push in on that. Frame counter was rarely accurate, but I did feel the tension when it came to the end of the roll and reversed it from there. Here's to hoping 🙂

I just tried the app you mentioned and I see what you were saying about it making calculations easier 🙂 Might end up using that one.

I would assume it does take in my lenses aperture into account with its calculations.

Ok not much was wrong. I ran a roll of film through (was ok wasting it) and I could definitely tell when it was done. Frame counter seemed to move slowly up to ~5 or so, but reverse really moved it far (all the way to the end). Not sure if that is the intended behavior, but yeah.

26 minutes ago, Dustin McAmera said:

In normal daylight conditions, exposure for digital and film will be the same. You could certainly use the readings from your phone or any digital camera like a light meter. I have installed an app called Light Meter, by WBPhoto  (my phone is Android - I suppose the same app is available for IPhone). It uses our phone's camera as a meter, and presents the results in a convenient way that doesn't need you to do calculations (convenient-ish - I preferred another app that I can't get any more). It has a few other features, mostly that I haven't used.

 

My issue is, my camera only goes down to 1/200 for shutter speed. According to the Sunny 16 rule, I feel like that stops me from using ISO 400 film. Maybe if I go up to f/22 (the far end of what my camera can do) it would be better?

My phone camera, on the other hand, is a static f/1.7, a dramatic difference. I got an exposure calculator app that lets you plug in an initial set of ISO, F-stop, and shutter speed, and then a desired new settings for two out of three, and it will give you the value for the third. Is this a good tool?

To note, aperture and shutter speed on my camera both have to be set manually.

20 minutes ago, Dustin McAmera said:

I think you may be talking about reciprocity failure , which is a thing for film. Under normal conditions of light, if you close down the aperture by one stop (from f/8 to f/11, say, or from f/2 to f/2.8), doubling the exposure time gives the same overall exposure. However, if the light is very low, and you're using a long exposure time, this relationship may break down. The film doesn't record light as effectively if it arrives at a very low intensity. Typically, you don't need to think about this for exposure times shorter than about a second. Where it begins, and how much you need to increase the exposure by, varies from film to film. If you need to know this sort of thing, the film makers usually have a data sheet that you can download; or it may even be printed somewhere in the information on the inside of the film box.

Thanks 🙂 I guess, the question which I should have asked at the beginning: is there any way I could use a manual camera app on my phone (which lets me change the ISO and shutter speed), and then do some calcuations as to what settings I should use on my manual camera? Or is there too much of a difference? I know what the aperture the lens is (as well as the model of sensor).

The frame counter seems unreliable (or at least does not move in the way I expect). In playing around with it, it seems to go up, but mainly when the film is being reversed? Probably not what's intended. Maybe those washers were important, lol.

There's a really old thread here that appears to be someone who was in a similar boat: 

Perhaps, I could open up the one I got off eBay and compare to see where the washers should go. It's rusted to all hell though (or at least some components are stuck) so it's gonna be a doozy to take apart.

Thanks 🙂 When I got it it actually had a broken takeup (or at least missing a piece?). But I bought another one off eBay. I was originally planning on replacing it but the eBay one was in much worse condition. At least it had a proper takeup though. 🙂

I took apart my original one and lost two washers before I saw where they went, but I don't think they were critical as all other functions seem to work.

You can see my other thread on the camera to see it (and me originally thinking the shutter blades were a crack lol).

Just now, tony_parsons1 said:

It may be that the blank spaces between the frames are confusing you - these are not an intrinsic part of the film, but exist as unexposed areas when each frame is wound on. Although there are frame numbers encoded along the perforations (i.e. 6, 6A) these are merely an indication to a lab for when reprints are requested. The reason that they are in pairs is to cope with the smaller frames (18x24mm, as opposed to 36x24mm) which are produced by half frame cameras.

Also, many cameras have a coloured marking near the take-up spool, indicating where the tongue of the film protruding from the cartridge should be placed for the wind-on mechanism to work correctly. BTW, which model of camera are you using ? If you look in the manual, there may be more helpful information contained therein.

HTH

I have an old Ikonta I got at a flea market. The manual wasn't much help in this, but I do think I understand more now.

I do think the frame counter on it is broken though (or at least nor reliable). Will I be able to tell with tension when turning the advance knob ones I reached the end of a roll of film?