If you're looking at buying a new piece of equipment, you will likely just look at the spec sheet and compare it to something similar. But even the numbers don't tell the full story.
This issue isn't exclusive to photography — far from it — almost every type of product will have some marketing intervention in the spec sheet to repackage a less than appealing number into something more impressive. That is, usually changing something understandable and unimpressive into something confusing. One strong example of this is the MPG in a car. You will often see a maximum MPG which is created very carefully on motorways or highways at the optimum number of revs and so on. (Side note: it used to be much worse than this but now the figures have to be more or less recreatable to stop manufacturers taking their cars into some windless aerodrome for ridiculous numbers.) The "combined" figure is usually the most accurate, but even that will be tough to replicate for many cars.
The photography industry has many similar misleading stats on spec sheets, some are just as famous as MPG in cars, and some are lesser-known. One of the most famous is, of course, megapixels. There are so many important factors to consider that influence the quality of an image, that a 12-megapixel camera can produce sharper images than a camera with more than 3-times that. However, the stat that irks me the most is one I was glad to see the Northrups brought up: the number of screen dots. Perhaps there is a good reason to discuss the number of dots on a screen that is too nuanced for me to know, but it just seems absurdly misleading to me. My Sony camera's rear screen has 920,000 dots which is impressive. That is until you realize my mobile phone has over 10,000,000 dots.
What spec do you find to be the most misleading?
All of the Northrup’s points are valid I think.
The spec that short-changes most is surely the lens f number and light-gathering. Lens designs are registered and they sometimes show lenses marketed, for example, as f1.4 actually designed as f1.5. Dxomark used to test lenses and they showed a lens sold as an f1.4 actually transmitting only T1.7. The simpler design of a f1.8 can deliver close to T1.8 which makes the f1.4 a very expensive upgrade if you want light gathering as well as shallow depth of field. I suspect if someone with the know how tested and published actual f and t stops a few manufacturers would quickly have to revise their claimed specifications.
I figure the most frustrating spec in photography equipment is guide numbers for flashes, expressed in meters and feet with ISO numbers and focal lengths that don't match up while comparing flashes.
Also it seems guide numbers are generally overestimated.
Good video. I think the “full frame equivalent” should be mentioned too. Many manufacturers state their focal lengths in full frame equivalents, but not f-stops. Fine if you do “real” specs or full frame equivalent, but not to cherry pick when to use which ones. Nikon claims the P1000 is 3000 mm and f2.8 at the wide end, but if 3000 mm is to be used, then the f-stop would be f/15.6… And at 3000 mm the maximum aperture of f8 is the equivalent of a whopping f/44.5!
I don't think that the f/44.5 at 3000mm is correct. It's f/8, which is frustrating enough. The shots are terrible at that focal length, but at f 44.5 you wouldn't get anything unless your ISO was really high (higher than the camera can go, which, if I remember correctly, was 6400), and your shutter speed really low. The f/2.8 is for their shortest lens length. My sister had a p1000, and I experimented with it a bit.
The maximum focal length of the lens is 539 mm. As it is marketed as 3000 mm that gives it a crop factor of about 5.57. 8 * 5.57 = 44.56. If you think I’m wrong, please clarify where the math is incorrect.
I think you're misunderstanding something, but I'm not sure exactly what. The 35m equivalent focal length is a very real and legitimate conversion that's analogous to converting feet to meters or pounds to kilograms. It's also the "full frame equivalent" you want, because a full frame sensor is the same size as 35m film.
F stops OTOH, are ratios, and that ratio is based on the actual focal length, not the 35m equivalent focal length. That's why an exposure at f/4 is always an exposure at f/4 regardless of the focal length or the sensor.
If there's some reason you want to know the actual diameter of an f stop instead of the ratio that's a different spec. I suppose there's some sense to knowing the actual diameter in terms of diffraction, but you'd also need to know the pixel pitch of the sensor, so even in that regard there's not a straightforward 35mm equivalent; IOW f/44.5 wouldn't always be f/44.5. And once you find out that your tiny little 18MP sensor is diffraction limited at f/3.2 there's still the question of whether that's more important than the depth of field or improved lens performance when you stop down to f/4 or f/5.6.
The bottom line is that, as near as I can tell, you're asking for a meaningless spec.
The f-stop is defined as the focal length divided by the aperture diameter. You by changing one of the inputs (focal length) the output HAS to change. By saying that f4 is always f4 you could also say that 539 mm is always 539 mm and never 3000 mm.
To use your example of converting between kilograms and pounds: If a car weighs 1000 kg and has 1000 HP, then it has a power to weight ration of 1:1. You can’t then say that the car weighs 2204 pounds and still has a power to weight ratio of 1:1. That would imply that the engine suddenly has 2204 HP.
Where this becomes a practical issue is when people expect the P1000 to have the same light gathering abilities as as a full frame camera with a 3000 mm f8 lens, which of course is not the case. The spec I’m asking for is not meaningless, it’s the only one that makes sense
Also, the Northrups have videos explaining this as well, which is why I’m surprised they didn’t include it in this video.
I think maybe you're confused about how exposure and f stops work. There's a reason that an exposure that's correct at f/4 on a 600 mm lens is also correct at f/4 on a 60mm lens even though the area of the aperture on the 600 mm lens is 100 times as big. The reason is that the narrower field of view from the longer focal length results in gathering light from only 1/100th the area the 60mm lens gathers light from. The result is that both lenses put the same amount of light on the sensor.
To make it simple, imagine taking two pictures of a large white wall uniformly lit by the sun. With the 600 mm lens you capture an image of a 1 by 1.5 foot section of the wall, and with the 60 mm lens you get an image of a 10 by 15 foot section of the wall. IOW you're taking a picture of 1.5 SF of reflected sunlight and 150 SF of reflected sunlight. Do you understand why it would be a problem if the smaller aperture of the 60 mm lens gathered as much light per SF of wall as the aperture of the 600 mm lens did?
I think you're having some similar confusion with the weight analogy. A 100kg car with 100 hp will have the same power to weight ratio as the 1000kg car with 1000hp. You can swap units for pounds and watts, but it's the ratio that matters, and the resulting performance will be the same.
The focal length of a lens doesn't change though - even on a crop sensor vs full frame. The length is still the same distance. On a 50mm lens, the light rays converge at 50mm from the element on any camera.
As Steve says, what changes is the field of view. That field of view is *equivalent* to the field of view on Full frame, but the focal length doesn't physically change. And as the aperture is also physically the same mm, the f-stop is also correct.
However, as you're on a narrower field of view - the sensor collects light from less of the lens - so the exposure will be less. Therefore for calculations, you can multiply the fstop by the crop factor too, bot neither actually, physically change
OMFG, not ANOTHER piece of clickbait trash from these two idiots...
Well I guess some people already know everything there is to know about cameras and photography in general. Personally I learned a number of things from this video and from many others produced by the Northrups. My suggestion to those who already know it all, don't view these videos.
Edison who?
You seem to wait with bated breath to negatively comment on every video from the Northrups. Seems like an odd obsession. I think we all get it by now. You don't like them, but don't seem to offer any worthwhile content yourself.
Some people do find value in what the Northrups do. If you don't, that is fine. That doesn't make them idiots. You don't need to personally trash them. I had some interaction with them several months ago, and found them to be very helpful and courteous. Maybe you can extend to them the same.
Respectfully, it might have something to do with trashing another photographer.........I wont troll the Northups but I know longer trust or view their videos..........
I'm not going to run around bashing them, but I decided a while ago that the signal to noise ratio was usually too low, and I feel like they're more interested in quantity than quality. To some extent that's true of most photographers who have a YT channel. It's a significant part of their income for a lot of them, and the value of the clicks isn't related to the value of the content. Even worse is when they're supplementing the YT ad revenue with revenue by promoting things in the video, so that the useful information comes with an extra serving of advertising.
Just to be clear. I have a disinterest in whether or not people like the Northrups' videos. I understand that some might think being prominent on YT invariably opens up the possibility of compromise of one's objectivity. I simply believe that ad hominem attacks based upon whether or not people agree with the content, without knowing anything personally about the video creators, is uncalled for and disturbing.
I don't have the professional background some of you have but first thing that came to mind is MP count or resolution. Most of my life thought higher mp equals higher image quality, even sold phones for 4 years and that's what the average consumer seems to think.
Learned there are a lot of factors that go into image quality and that a bad camera can output 4k video that contains less detail than another camera at 1080p due to terrible video quality. Same with photos, higher mp doesn't always equal more detail or ability to crop.
I've long figured that MP are sort of like the weight of meat, and if camera manufacturers sold meat they'd be trying to convince you that a Burger King quarter pounder was better than a 3 ounce piece of filet mignon.