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

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

What are you basing this calculation on? Just curious. It was my understanding that the f-number has effect on DOF, but can focal length have effect as well? Completely understand and completely agree. Was just curious about the differences. 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.

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. 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.

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. 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? 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? Thanks for this info! That does make sense. That does sound like a plausible explanation. 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!

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.

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

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?

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.

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.

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).

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?