Why lenses are LYING to us!!
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- Опубліковано 9 вер 2024
- INSTAGRAM: dpmphotographs
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Excellent content! Without any bla bla right to the point. That's how I like it. 😃
Haha, skip the foreplay and get down to business 🤣🤣🤣
@@DaveMcKeegan No skipping. Liars have to be exposed... 😂
I love this ! I watch again and again, every six months, and feel as if I understand my lenses...Until I watch this wonderful video again...
Nice video Dave, thanks for uploading it.
In regards to sensor size and effective focal length, I find this really confuses a lot of newbies. It either is confusing to them or sends them into a rage when they find out that even lenses that are made only for a crop sensor cameras also have to have crop factor applied to them. It's all based on the measurement system that is industry standard, as explained in your video. But then, they seem a little loose with that standard in regards to lenses that when compared to others that should be the same but are not, also shown in your video.
Great stuff, Dave. I appreciate how you don't try to talk down to the audience and you give all the good geeky details. It's a big help for those of us that are interested in the details beyond the UA-cam & manufacturer hype machine.
Thanks Gerald, it's always good to hear that I'm doing something right 😁
Well explained overall Dave! Thanks for reminding that aperture has no true relationship to light gathering. This is especially true with the recent bad trend of over-corrected lenses from Sony, Canon and Sigma (Fujifilm, Voigtlander usually have less elements for better transmission, depends on the lens of course)
Lenses should indicate their angle of view or in the case of zoom lenses the their widest and narrowest angle of view for a specific size of film or digital sensor. For many many decades until the digital photography, the 135 film was the standard in photography and nearly all professional or amateurs were using this kind of film. So from experience they knew the corresponding angle of view of every focal length. That has continued in the digital age with various misunderstandings due to the various sizes of digital image sensors.
For infrared photography the focus scale of all modern lenses is wrong because it is made for the visible spectrum. Some much older lenses of the film era have additionally a red focusing scale for infrared photography. For ultraviolet photography things are even more complicated with lenses.
Also the ISO of the digital cameras is rarely right. It is usually much less. It is a marketing trick because most consumers prefer cameras with higher maximum ISO.
DXOMARK website indicated the right ISO of most digital cameras.
I'm going to have to disagree with you on that. One of the best features of Canon's DSLRs was that their full frame lenses mount naively to their crop bodies, and some of Canon's bodies use sensors that are larger than APS-C, but smaller than full frame. Listing field of view is just a can of worms that going to cause nothing but confusion, and that's not even getting into the conversion factor.
And as for ISO, the definition these days is largely arbitrary as everyone builds their sensors differently, but what is more universal are stops. Everything else being identical (body, lens, focal length, f-stop, flash power, and ambient lighting), something shot at ISO 1600 should be exactly 16 times as brighter as something shot at ISO 100.
Zeldagigafan However APS-C Canon EF-S lenses can't be used on full frame Canon dSLR camera bodies.
The content quality of your videos keeps growing. Thanks again mate, great video and crystal clear information. Cheers!
Thanks Matt, glad to know I'm going in the right direction 🤣
1:37 The focal length really is not any physical measure of the lens. The simplest way to understand the focal length is to think the lens as a simple convex lens. If the lens is focused at infinity the focal length is the distance between its center and the imaging plane. For a complex lens the focal length is the same as would be for a simple lens that produces the same size of image. Lenses are complex to prevent distortions like chromatic aberration or because the physical realities demand it like if one needs to design a 10 mm lens for a DSLR with 44 mm flange focal distance.
Can you talk about distortion correction baked in to raw files and how that affects the images? I'm noticing a lot of cheating/lying going on there too.
Un peu ardu, mais passionnant. 1st time i'have been explained so clear (t-stops and transparency of glass). A bit tough for me but so good to learn. Merci et continuez.
Great content! This video really cleared a few questions I had about my lenses and why things were not adding up! Very well explained, I finally get it! lol! Keep them coming!
Fascinating discussion, Dave! I noted the same discrepancy in my own copies of the Sony28 f2 and the Tamron 28-75 f2.8. The Sony lens is definitely wider by quite a bit!
Happens between quite a few lenses - sometimes it's a combination of discrepancies in the true focal length + focus breathing if you aren't testing them at infinite focus
Good stuff! (As always....great info......)
That's what I stumbled upon often and you put it into 1 video! Thanks.
I wonder how different that can be when using a light meter... it's always gonna be off, except you calibrate it for every lens, right? Crazy...
Thanks for taking the time to explain this! In particular the quoted focal length and how this can differ in field of view between different sensors.
You're welcome Will, hope you found it useful
i was thinking you would say something stupid based on the title.
but man, you nailed it.
good job.
Thanks Ahmed 😊
I've always read the Sony 28mm 2.0 is more like a 26mm lens. I never thought to compare it with the Tammy, but if so, maybe I'll keep it in my bad if I need to squeeze a couple more mm out of a shot...
Yes I also read that somewhere that Sony actually made the FE 28mm around 26mm in order to compensate the barrel distortion. So when its corrected its become a 28mm lens 😀 cmiiw
I was just think about how could add a flip screen without copying canon.
What if sony add a hinge to flip the screen while still having their tilty up and down screen
Sony had a flip screen design very different from Canon back on their DSLRs
It would rotate up over the top of the camera and then be rotatable from up there
But not sure if Canon have patents on all flip screens and have now just decided that they don't want Sony having them because they are becoming threatening to their market share
I have 3 lenses that can do 35mm. A 35mm prime, a 18-35mm zoom and a 17-55mm zoom. The 35 and 18-35 both produce an image of the same size. The 17-55 at 35 creates a much larger image. It's weird.
Excellent work on content. You put that together well. Good work! Subscribed!!!
Thank Kevin, glad you enjoyed it, welcome to the channel 😊
Thank You Dave. My brain is full now. Time to 'digest', watch it again with sample lenses in hand.
Haha, sounds like a good plan Al 😉
The puppy is awesome! A true star!
Nice video, many photographers doesn't take this in mind. I'll share.
Maybe the ISO needs to step in and introduce a more accurate, unified measuring system for lenses like it did with film when there was ASA and DIN (the US and German standards organisations). If focal lengths are given as 35mm equivalent, and yet most camera users/photographers today have never even used a 35mm (or full frame) camera, it is a fairly pointless reference anyway. What would make more sense is to label a lens by its angle of view, which is what we really want to know. T-stops could be the standard instead of f-stops, again because that's what we really want to know. And a lens can't be labelled as macro unless it was actually capable of shooting at 1:1, otherwise it would have to be called close focussing with the magnification ratio displayed. Like the change from imperial to metric it would require a period of adjustment but people would soon get the hang of it.
I did consider if it would work quoting all lenses by their angle of view, however this might cause confusion with longer focal lengths where the changes in angle is very small
It may muddy the water even more on the differences between bridge cameras and ILC's ... Plus it might throw a spanner in the works on depth of field calculations
@@DaveMcKeegan I can't see how it could cause more confusion than already exists? In fact, it would create less once people adapted to the new standard. As you already pointed out in your video, the written and actual focal lengths are often different. If a lens has to have an ISO rating then it is an accurate standard. OK, sensor ISO "speed" ratings are not really the same as those of film and are just calculations based on gain applied to the sensors base rating. For fixed lens cameras, calculating the angle of view (aov) would be an easier measurement than for interchangeable lenses, especially for lenses like Canon EF that will work on both full-frame and crop sensors. Maybe it would better to give a removable lens spec in both actual focal length and aov. Let's face it, there isn't really an actual international standard for lens measurement, there is the one that the lens maker apply based on a traditional scientific/mathematical calculation that has a general agreement and acceptance. Market stalls and some shops still show weights in Kg and lbs, with different adjusted prices. Car speedos still show kmh and mph, and yet most people really don't have a clue how fast they are driving, or really have an accurate perception of distance.
Which does bring up the point of working out the depth of field. As it is simply a mathematical calculation, it would just be a matter of changing the parameters of the formula, which is again as much dictated by the sensor/film size as it is by the aperture and focal length, whether expressed as f-stop or t-stop, or as mm or aov.
Anyway, nowadays sales and marketing seem to trump science, so the majority will go with what the advertising and packaging says, while us nerdier types are left scramble around finding the actual specs. Still, it's all food for thought, and I've probably overthought it and it's left me feeling a little queazy.
@@chrispatmore8944 because the depth of field is calculated based on aperture diameter, however angles of view can be the same on different focal lengths with different sensor sizes so you wouldn't be able to calculate it - and while for example the Sigma 85 1.4 has the same T-stop as the Sony 1.8, it still has the physically wider aperture so produces a shallower depth of field
@@DaveMcKeegan I imagine there are very few photographers who actually sit down and calculate the depth of field before taking a photo. They will look through the viewfinder and make the appropriate adjustments, plus use their experience of choosing the right lens etc. to get as little or as much in focus as they require. As long as you know you the basic principles of photography and are familiar with the limitations of your equipment, all the technical specs are not that important when getting the results you want, depending on what you are shooting. I'm sure photography has become more complicated since the advent and advances in digital photography, and they have to keep the cameras more complex to make them easier to use. If I wasn't shooting in badly lit music venues all the time, where using a flash is not desirable, and sometimes not permitted, and the fast turnaround times, I'd happily stick with using my simple, old OM1 and prime lenses.
@@chrispatmore8944 I totally agree Chris, no one would sit down to actually work out the d.o.f
However you'll still likely get people looking between a bridge and DSLR and seeing the lenses have the same T-stop value and same angle of view and then unsure why they produce such different images
The only workaround I think would be to state the physical focal length and then change the "35mm equivalent" for "angle of view"
Wouldn't the actual point of convergence differ based on what design was used in the lens? Meaning that the nominal focal length is just an equivalence, not the real distance. That being the case, different lenses being slightly different should be expected.
0:32 As you said, lying is a "strong term" since there is a tolerance for every specification that's out there. That goes for weight, length, filter thread and the sodium in your brand favourite potato chips. I doubt even a $12000 600mm lens is actually 600. T-stops is also a "lie" because it simply indicates an average and we all know that light distribution is rarely even, particularly for a wide-open lens. As for "macro" well the manufacturers (marketing department) gave us what most would-be photographers wanted to know: can I get close-up shots? Most people are really NOT interested in 1:1 magnification because it's difficult to work with. Macro simply tells the uninitiated that the lens/camera can do close-up.
If you must have accurate specifications with stated tolerances, buy calibrated scientific equipment.
"close up" is also quite subjective. I have a couple lenses that are marked as Macro, but their minimum focus distance is 1 meter.
Very good. Finally someone who gets it all right.
Now could you explain in your extremely accurate way what a standard lens is for a particular type of sensor ?
I think that too would open some eyes.
Great Vid btw :)
so, no one will acknowledge the glorious napping stance of the dog uh?
wrong on the f stops... what you thinking off are the t stops
f stops have nothing in commen with light only with DOF
Thanks for the clear lesson. Superb job. Very helpful. Thanks!
Thanks Don, glad you found it useful n😊
Wow. That shows how much we don't know :) did not know about T stop.
Thanks
great video and info as most folks have no clue about this stuff and get scammed by sales people to buy stuff they think is great when its not
Awesome vdeo.
15:57 Yes.. Question: Could you repeat everything you just said?
Hahah, yes but most people get sick of me talking for half an hour 🤣
Very clear, modt of it at least, cleared up a few of my questions. Thanks
You're welcome Jimmy
Out of curiosity what bits weren't clear just so I know for future reference
Dave McKeegan i dont think it was your explanation i think it was me, the macro part was hard for me to understand, more specifically the 1:? Ratio i didnt reall understand why the ratio on a macro lense was 1:1
Wow. Now I understand better a lot about objectives. Thanks!
Excellent video! So many things I've noticed and wondered about explained :)
Thanks, glad you found it useful 😊
Very informative. Very clear. Thanks for this. Cheers!
You're welcome Muata, glad you enjoyed it 😊
How is the focal length measured for pancake lenses. Like the 40mm pancake for Canon. Where do the light rays cross? Another question is how can they create a constant aperture lens like the 70 200 2.8? If the aperture is 2.8 at the long end why isn't the aperture bigger at the wider end?
The point of convergence is measured from the sensor - the Canon sensor is 44mm behind the lens mount, so the lens projects the point of convergence 4mm behind the lens
And lens with a focal length shorter than the flange distance will have its point of convergence inside the camera body
In regards to aperture, it's because the exact science behind measuring it isn't measure the diameter of the hole inside the lens, it's to measure the size of the hole as seen from the front of the optics
If you look down a 70-200 while you zoom, because it's internal zooming and the moving back, the apparent size of the hole is magnified so it appears bigger as you zoom)
Variable aperture lens will see a small increase in size but no where near as much - hence the ratio increases
@@DaveMcKeegan thanks for clearing that up. :)
Perfectly clear explanation, thanks Dave
You're welcome Jean-Claude 😊
Very technical...keep it coming!!!
Thanks Toney 😁
Excellent! Thank you.
Inside the lens there are many glass elements ... You mean lenses? The whole thing should be called a "lens assembly" but I guess it's easier to just call it a lens.
Well explained and very concise.
Thanks Adam 😊
Good, clear explanation of this.
Thanks Joe 😊
Nice video bro not all youtuber do this things and explain it
I like that dog-shaped pillow, can you provide an amazon link?
Unfortunately it's not available on Amazon, it's a hand crafted, one of a kind walking pillow 😜
@@DaveMcKeegan omg, it moved at 6.42! *mind blown*. :D
@@chrissoclone it is a remarkable pillow ... Although not the most convenient when it's licking your face at 6am because it wants to in the garden 🤣
*Lies maketh the world go round* - yay
*Inserts abuse telling Dave to shut up*
*Doesn't understand if other posters will absolutely flame me or understand how this channel roles*
*Deletes original written comment*
Thanks for the upload man, I hadn't even really thought about this before.
Do dxomark still test lenses? Last time I looked their database was woefully outdated.
Yeah they are still testing by the looks of it, they been recently adding the RF & Z mount lenses
@@DaveMcKeegan I was wondering what they'd make of the Tamron 28-75 f2.8 on the Sony. Seems like they're too busy with mobile phones to bother
I still think Nikon is right and these lenses should be called “micro” because they show things at a microscopic (i.e. life size or larger magnifications) level.
Not sure, as microscopic refers to objects that are too small to be seen with the human eye, whilst macroscopic is objects that can be seen with the human eye that are just made larger
Hence microscopes usually deal with things like bacteria etc
It seems your dog is not too much into long conversations...lol
Haha, it was quite late when I recorded this, think he was ready for bed
Well beside my head hurting, I think I have a better idea. About what and why? Not sure. But will have to chew on it for awhile.
Apologies for the headache Allan 😁
very nice video
Thanks Rich 😊
i didnot understand a word
So what can we take from all this?
Simple - Who. Cares?
Quit worrying about the little things, LEARN your gear, LEARN the capabilities and limitations, and then go out and have fun capturing "Your" view of the world around you.
And i thought this was clickbait...
Superior presentation of content.
Thank you 😊
Sorry to be the turd in the punch bowl (the rest of your content is quite helpful), but there's a pretty big misconception in your video. At around 5:28, you state that the F number is a ratio between focal length and the aperture diameter. The diameter represented in the ratio is actually of the entrance pupil; the diameter of the aperture as viewed from the front of the lens. Gerald Undone has a great video explaining this(it's an extremely common misconception), and also why this seemingly small difference can lead to some dramatically incorrect assumptions. ua-cam.com/video/OaSq0ES1ArE/v-deo.html
Who cares? How does this affect picture taking?
Maybe someone isnt happy with the pictures they are getting so decide to change to what looks on paper to be a better lens that could in fact have absolutely no affect on the pictures being taken
Casing point the mentioned 85mm's - maybe someone has the 1.8 and decides they want the 1.4 for better low light - but in reality there is no difference at all
You are confusing macro lenses with lenses with “macro“ option... only beginners do so... hope them are your target in that video...
Yes it's for anyone who ever thought "it must be a macro lens because it has macro written on it" - of which I know a few people who have done exactly that
The picture quality of the Sony is really bad. Your hands looks bloody reddish.
To be fair that's probably more down to me than the camera. If you look at what some people are able to achieve with Sony you can see the potential is there in the camera, I just can't fully extract it 😂
@@DaveMcKeegan First let me thank you for interacting with your audience. okay, so it seems that the sony color science need a lot of work in post production.
arguably yes, although I shot this in a log picture profile which would require work in post regardless of what camera you shoot with - I created a custom lut to apply to the footage which generally gives a decent look however the lighting isn't always consistent where I'm shooting so can sometimes skew the results
First
+10 points 😁