[normhead]

They have all been in response to people quoting him.

HIs error is really simple. When he claims the larger sensor uses more light and therefore has better lower noise performance etc. he uses images with different DoFs. If you normalize the DoF, then at least between APS_c and FF, noise is the same, low light performance is the same, total light is the same. Something he manages to get through a whole "tutorial" without mentioning. In fact he comes up with some cacamainy nonsense about how ƒ2.8 on a small sensor should be labeled as ƒ8 or 16ƒ because that would be the equivalent DoF, even though ƒ stop is an exposure value not a DoF value. He is seriously confused about some of the finer points in photography.

In this video he's pretty good because he does what I think everyone should do. "Just look through the viewfinder, see what you can do." If he'd stick to that, he's actually seems like a pretty good guy.

The good that he does with "how to tutorials" is pretty much cancelled by his theoretical nonsense. It makes it impossible to recommend him. Now if he'd delete everything that has to do with "total light" etc. then we're good.

I'd recommend him for tutorials like this one, but then someone might wander onto one of his nonsense tutorials and that would ruin everything.

I'd prefer that he just not be mentioned at all.

---

Last edited by normhead; 07-14-2016 at 10:47 AM.

[uday029]

I thought f-stop was used for both, combination of exposure and DOF. No? Generally in ANY tutorial, they explain the concept of DOF by f-stop. Higher f-stop for more DOF and vice versa. Atleast, that is how I interpreted it by learning photography from a ton of youtube videos. F-stop controls both exposure and DOF. Isn't T-stop the true measure of how much light a lens lets in? So, is some other factor by which you measure DOF? For a non-technical and not too "sciency" photographer like me (most of the beginners are), his explanation completely makes sense. Different sensor sizes create different DOF at a given f-stop. Atleast, it made sense when he told it. May be I am missing something.

How would you measure DOF? Because when ever I asked anyone (even on this forum) about how to get blurred background, the answer was "Use lower f-stop". So for me, as I am learning photography, f-stop became synonymous with DOF. May be every one is then learning photography the wrong way.

They have all been in response to people quoting him.

HIs error is really simple. When he claims the larger sensor uses more light and therefore has better lower noise performance etc. he uses images with different DoFs. If you normalize the DoF, then at least between APS_c and FF, noise is the same, low light performance is the same, total light is the same. Something he manages to get through a whole "tutorial" without mentioning. In fact he comes up with some cacamainy nonsense about how ƒ2.8 on a small sensor should be labeled as ƒ8 or 16ƒ because that would be the equivalent DoF, even though ƒ stop is an exposure value not a DoF value. He is seriously confused about some of the finer points in photography.

In this video he's pretty good because he does what I think everyone should do. "Just look through the viewfinder, see what you can do." If he'd stick to that, he's actually seems like a pretty good guy.

The good that he does with "how to tutorials" is pretty much cancelled by his theoretical nonsense. It makes it impossible to recommend him. Now if he'd delete everything that has to do with "total light" etc. then we're good.

I'd recommend him for tutorials like this one, but then someone might wander onto one of his nonsense tutorials and that would ruin everything.

I'd prefer that he just not be mentioned at all.

[normhead]

I thought f-stop was used for both, combination of exposure and DOF. No?

Definitely not. There is a specific formula that describes exactly what an ƒ stop is, and DoF is not in the formula. The reasons Northrup and friends are so confused, is they are skirting around the edges of two different issues trying to make them one, and then making false conclusions because of the consequences of those assumptions.

How would you measure DOF? Because when ever I asked anyone (even on this forum) about how to get blurred background, the answer was "Use lower f-stop". So for me, as I am learning photography, f-stop became synonymous with DOF. May be every one is then learning photography the wrong way.

DoF is the distance between the nearest and furthest points in acceptable focus. It is a distance. So while related to Aperture, it's not the same as aperture. Aperture is related to light intensity.

So at a given f-stop, the light intensity on the sensor is the same, for APS_c, FF or MF, however, the DoF is not.

Just as good an answer to your question would be, use the same lens on a larger format camera. That would just as effectively decrease your DOF assuming they are like APS-c and FF and the lens's image circle covers the sensor footprint of both formats.

Take an FA 50, 1.7. You have an image exposed at ƒ2.8 on APS-c, and you want narrower DoF. You can plunk your FA 50 on an FF and have narrower DoF on a K-1. Or you can take the image at ƒ2 on APS-c.

IN that particular example. both images will use the same total light and have the same noise, if you adjust the ISO to keep the shutter speed the same. Not only is the DoF the same, but because the APS-c is being shot at a faster aperture, the total light and noise are also the same.

The linear relationships between ƒ-stop and DoF are broken as soon as you change formats, but are consistent within each format. SO as long as you are discussing things within the context of one format, there is a direct link between DoF and Aperture. The mistake , you and Tony and many others are making is you are trying to create some kind of cross format theory that ignores half the equation.

[uday029]

Ok. So you and I are saying the same thing. You said that in order to get same DOF b/w formats you change from f 2.8 to f2. That is precisely what I was saying but you said it better. I said "Different sensor sizes create different DOF at a given f-stop". So I guess, the differences are arising in how someone interprets the definition or workings of "f-stop". If someone was defining f-stop (could be a wrong interpretation/explanation based on how DOF concept is taught universally) as a factor that controls DOF, then a f2.8 lens on APSC is not the same as f2.8 on FF. If I have a f1.2 lens and want same DOF look as a full frame, then there is no way I can reproduce it on APSC as the lens aperture does not go bigger than f1.2.

You and I both were measuring DOF using an "f-stop". Formula for determining f-stop might not have DOF as one of its variables but we all are indeed measuring DOF using f-stop. So, if I want a f2.8 + FF DOF on an APSC camera, should I ask for a lens with "f 2.0" aperture? If not, I will never get the same DOF if I am stuck with f2.8 lens. So if someone is telling me that a particular lens is "f 2.8", they are referring to both exposure and DOF. I say this because in all the ads touting f2.8 or f1.8 capabilities, brands advertise using a beautiful portrait with blurred background and not light gathering capabilities. So I am not correct in saying that f2.8 lens on FF is not f 2.8 on APSC purely in terms of DOF? Again, I am talking this in terms of how the photography industry is wanting me to believe what a particular f-stop can do - i.e, create beautiful photos with blurred background or have everything in focus.

So I guess we should stop everyone from measuring DOF in terms of f-stop.

Definitely not. There is a specific formula that describes exactly what an ƒ stop is, and DoF is not in the formula. The reasons Northrup and friends are so confused, is they are skirting around the edges of two different issues trying to make them one, and then making false conclusions because of the consequences of those assumptions.
How would you measure DOF? Because when ever I asked anyone (even on this forum) about how to get blurred background, the answer was "Use lower f-stop". So for me, as I am learning photography, f-stop became synonymous with DOF. May be every one is then learning photography the wrong way.



DoF is the distance between the nearest and furthest points in acceptable focus. It is a distance. So while related to Aperture, it's not the same as aperture. Aperture is related to light intensity.

So at a given f-stop, the light intensity on the sensor is the same, for APS_c, FF or MF, however, the DoF is not.

Just as good an answer to your question would be, use the same lens on a larger format camera. That would just as effectively decrease your DOF assuming they are like APS-c and FF and the lens's image circle covers the sensor footprint of both formats.

Take an FA 50, 1.7. You have an image exposed at ƒ2.8 on APS-c, and you want narrower DoF. You can plunk your FA 50 on an FF and have narrower DoF on a K-1. Or you can take the image at ƒ2 on APS-c.

IN that particular example. both images will use the same total light and have the same noise, if you adjust the ISO to keep the shutter speed the same. Not only is the DoF the same, but because the APS-c is being shot at a faster aperture, the total light and noise are also the same.

The linear relationships between ƒ-stop and DoF are broken as soon as you change formats, but are consistent within each format. SO as long as you are discussing things within the context of one format, there is a direct link between DoF and Aperture. The mistake , you and Tony and many others are making is you are trying to create some kind of cross format theory that ignores half the equation.

[normhead]

Ok. So you and I are saying the same thing. You said that in order to get same DOF b/w formats you change from f 2.8 to f2. That is precisely what I was saying but you said it better. I said "Different sensor sizes create different DOF at a given f-stop". So I guess, the differences are arising in how someone interprets the definition or workings of "f-stop". If someone was defining f-stop (could be a wrong interpretation/explanation based on how DOF concept is taught universally) as a factor that controls DOF, then a f2.8 lens on APSC is not the same as f2.8 on FF. If I have a f1.2 lens and want same DOF look as a full frame, then there is no way I can reproduce it on APSC as the lens aperture does not go bigger than f1.2.

You and I both were measuring DOF using an "f-stop". Formula for determining f-stop might not have DOF as one of its variables but we all are indeed measuring DOF using f-stop. So, if I want a f2.8 + FF DOF on an APSC camera, should I ask for a lens with "f 2.0" aperture? If not, I will never get the same DOF if I am stuck with f2.8 lens. So if someone is telling me that a particular lens is "f 2.8", they are referring to both exposure and DOF. I say this because in all the ads touting f2.8 or f1.8 capabilities, brands advertise using a beautiful portrait with blurred background and not light gathering capabilities. So I am not correct in saying that f2.8 lens on FF is not f 2.8 on APSC purely in terms of DOF? Again, I am talking this in terms of how the photography industry is wanting me to believe what a particular f-stop can do - i.e, create beautiful photos with blurred background or have everything in focus.

So I guess we should stop everyone from measuring DOF in terms of f-stop.

Where I and Tony Northrup differ, is he claims there is a difference in total light, between formats, which he can say only by ignoring the change in DoF over formats.
Using the 50 mm example above
FA 50 ƒ ƒ2 ISO 100 and 1/100s is the same as
FA 50 ƒ2.8 ISO 200 and 1/100s

Same total light, same noise, same DoF , same shutter speed. Tony and others claim there is a difference in total light, and noise, by ignoring the change in DoF, A clever slight of hand used to obscure the truth.

[Pål Jensen]

Exposure, Iso, shutterspeed, Aperture, reciprocity, the concept of stops has nothing to do with formats or total amount of light. It is about light intensity. Anyone who doesn't get this is talking nonsense.

[biz-engineer]

For every shot with blurred background, typically short tele to long tele lenses where faster shutter speed is needed, there is not need to have the same DoF on apsc and ff. I have not issue shooting 135mm f2 on ff with everything I want in focus to be in focus. The only exception where you need to have everything in focus is landscape where you usually use ultra wide to standard focal length range , in which case shutter speed isn't much of an issue, or you use a tripod anyway in dim light, and in those cases, it is not an issue at all to use base iso and stop down the lens one f stop to get everthing in focus AND better DR from the ff sensor.

[normhead]

For every shot with blurred background, typically short tele to long tele lenses where faster shutter speed is needed, there is not need to have the same DoF on apsc and ff. I have not issue shooting 135mm f2 on ff with everything I want in focus to be in focus. The only exception where you need to have everything in focus is landscape where you usually use ultra wide to standard focal length range , in which case shutter speed isn't much of an issue, or you use a tripod anyway in dim light, and in those cases, it is not an issue at all to use base iso and stop down the lens one f stop to get everthing in focus AND better DR from the ff sensor.

In this case, that's simply incorrect. I shoot most of my macros and many other subjects at multiple ƒ-stops and select the one with the DoF and out of focus areas that best suit the subject, and that is often quite arbitrary. You often can't use just any ƒ-stop. Not if you want the best possible image.

[Tranzistors]

Normhead, Tony's theories do hold up, but it is true that the whole subject is very confusing. If you want to figure out what Tony actually believes about crop factors and such, take a look at his geeky playlist (https://www.youtube.com/playlist?list=PLwIVS3_dKVpv2-mVvxddngvv1oNszvMvS). I suggest to start from "ISO: The Ultimate Guide" and then watch videos with “Crop factor” in the title. Those contain corrections and addresses points that you have made. The clarifications are excruciatingly long, but it is well worth it.

[normhead]

Normhead, Tony's theories do hold up, but it is true that the whole subject is very confusing. If you want to figure out what Tony actually believes about crop factors and such, take a look at his geeky playlist (https://www.youtube.com/playlist?list=PLwIVS3_dKVpv2-mVvxddngvv1oNszvMvS). I suggest to start from "ISO: The Ultimate Guide" and then watch videos with “Crop factor” in the title. Those contain corrections and addresses points that you have made. The clarifications are excruciatingly long, but it is well worth it.

While I'm certainly glad to hear he's done that, I'll take your word for it that he's corrected his videos and stop trashing him accordingly, but, having paid to learn this stuff, and taken a year of my life to do so, I'm not inlined to spend much time on the theory. I sorted out what I needed to know and what I could take a pass on years ago.

[Not a Number]

All this fuss by people who haven't even watched the video. I don't own a K-1 but the more I can learn about it especially from people who have it in their hands the better my buying and use experience will be. You people blast critics of Pentax equipment who don't even use or have touched it - doesn't the same kind of go for criticizing a video you haven't watched? Who da thunk it?

As far as criticizing Tony for not being a Pentaxian because he doesn't use the eDials to navigate through the menus - well I've been using my K10D for 5-6 years coming straight from MF film cameras. Even though I know you can scroll through the menus with the eDials I seldom do. It is rare that I go into the menus that I can never recall which dial switches from menu to menu and which pages up and down. Many a time I have turned the wrong dial and had to start over from the top. At least with the 4-way controller up is up, down is down and left and right is left and right, respectively. Both Tony and Jordan of The Camera Store make note that the interface takes some getting used to but the customization options usually can set things to your liking. Tony even figured out a way how to do something he wanted to do during the video. What better way to illustrate the flexibility of the K-1 or Pentax user interface?

[Tan68]

Replying just to mark this for later review. Looks like a pretty comprehensive video.

forumati simply type 'tagged'
show offs type 'heuer'

[wizofoz]

All this fuss by people who haven't even watched the video. I don't own a K-1 but the more I can learn about it especially from people who have it in their hands the better my buying and use experience will be. You people blast critics of Pentax equipment who don't even use or have touched it - doesn't the same kind of go for criticizing a video you haven't watched? Who da thunk it?

As far as criticizing Tony for not being a Pentaxian because he doesn't use the eDials to navigate through the menus - well I've been using my K10D for 5-6 years coming straight from MF film cameras. Even though I know you can scroll through the menus with the eDials I seldom do. It is rare that I go into the menus that I can never recall which dial switches from menu to menu and which pages up and down. Many a time I have turned the wrong dial and had to start over from the top. At least with the 4-way controller up is up, down is down and left and right is left and right, respectively. Both Tony and Jordan of The Camera Store make note that the interface takes some getting used to but the customization options usually can set things to your liking. Tony even figured out a way how to do something he wanted to do during the video. What better way to illustrate the flexibility of the K-1 or Pentax user interface?

N.a.n. I don't think the critisism is because Tony didn't know (or didn't demonstrate knowledge of) the e-dial while navigating the menu's. It was, on my part at least, an observation that Tony, like most other reviewers, are not used to the Pentax way of doing things. As you pointed out, he found out where the fx1 button was during the video; clearly demonstrating lack of familiarity. I think it is to be expected. Pentax has not been top of mind for the reviewer class for as long as there have been video reviews, and now the K-1 is starting to garner some attention due to it's outstanding price/performance ratio. As a Pentax user for almost a decade, I learned nothing from Tony's presentation, but am awfully glad he has done it. It is rudimentary, aimed at newbies and the curious, but still useful as a piece of the advertising/marketing mix.

[Tan68]

I thought f-stop was used for both, combination of exposure and DOF. No? Generally in ANY tutorial, they explain the concept of DOF by f-stop. Higher f-stop for more DOF and vice versa. Atleast, that is how I interpreted it by learning photography from a ton of youtube videos. F-stop controls both exposure and DOF. Isn't T-stop the true measure of how much light a lens lets in? So, is some other factor by which you measure DOF? For a non-technical and not too "sciency" photographer like me (most of the beginners are), his explanation completely makes sense. Different sensor sizes create different DOF at a given f-stop. Atleast, it made sense when he told it. May be I am missing something.

How would you measure DOF? Because when ever I asked anyone (even on this forum) about how to get blurred background, the answer was "Use lower f-stop". So for me, as I am learning photography, f-stop became synonymous with DOF. May be every one is then learning photography the wrong way.

Well... aperture, noted as f-stop, is an element of adjusting exposure just as shutter speed is. f-stop as an element of exposure is the same for this lens or that lens. If you mount either a 50/1.8 set at f/5.6 or a 100/2.8 at f/5.6, you will use the same shutter speed to get the same exposure. I do figure you know this :^)

f-stop as a description of depth of field is not always consistent. That 100mm lens will give you a shorter depth of field at f/5.6 compared to the 50mm lens. However, mounting the 100mm lens will also give you a different (tighter) picture of your scene. If you back up until you have the same view with that 100mm lens as you do with the 50mm lens, the depth of field will be pretty much the same... f-stop as a comparison of DOF across different lenses depends on if you try to keep framing the same.

Keeping the framing the same is an element of the equivalence argument when comparing APS-C to FF using different focal lengths on each camera...

I don't think t-stop is another measurement of DOF. DOF is determined by aperture and this is described by f-stop. t-stop affects shutter speed. A lens at f/5.6 with a t-stop of 6.7 will let you use a faster shutter speed for the same exposure than a lens at f/5.6 with a t-stop of 8... maybe I misunderstand t-stop, but I don't think light transmission will affect DOF which is based on aperture, the physical opening.

---------- Post added 07-15-16 at 06:35 PM ----------

... So I am not correct in saying that f2.8 lens on FF is not f 2.8 on APSC purely in terms of DOF? Again, I am talking this in terms of how the photography industry is wanting me to believe what a particular f-stop can do - i.e, create beautiful photos with blurred background or have everything in focus. ...

Yes and no. Perhaps some maybe mixed in.

It depends on subject framing.

Will just swap the same lens from APS-C to FF with the same aperture and stand in the same location? FF will have greater depth of field.

Will you swap the lens from APS-C to FF and then take a few steps forward to keep framing the same? APS-C will have greater DOF.

Visit an on-line DOF calculator and use easy focal lengths like 50mm and 75mm (1.5x as crop is 1.5x to FF) and distances f 10 feet for the 50mm and 15 feet for the 75mm. Pick different sensor sizes and see how DOF changes when you take the picture with:
- same lens & same distance [for different framing and] different sensor size
- same lens but different distance for same framing with different sensor size
- same distance but different focal for same framing with different sensor size

[Tan68]

Hmm.. I thought there were a couple other posts here about depth of field. I didn't reply to them last night because I was hunting a web address to include in my reply. I don't see those posts now...

Working from memory, I think one post was that DOF was DOF regardless of what was later done with the image. Another post was that magnification of the image (display size) matters.

I agree with the second post I think I maybe recall reading in this thread. [DOF is DOF straight from the lens but what is done with an image when you get it home affects .acceptable. DOF so I suppose both posts have their point]

Display size and its affect on apparent depth of field is why people were saying some of the recent.. K1 bike test pictures are not valid. Focusing errors could be masked by the small display sizes posted [and the appearance of increased DOF] and focus tracking ability could appear better than it is.

This website allows print size and viewing distance to be set as a parameter. Click on 'show advanced'. By changing these parameters, the user is changing the circle of confusion. The user is defining or refining DOF to suit his needs and/or pickiness. A Flexible Depth of Field Calculator

The Cambridge In Color site is fine, uday029, but for the comparisons I suggested earlier, I recommend DOFMaster.com

+ uday029, this talk of display size and viewing distance doesn't have any real affect on your consideration of DOF and APS-C v. FF. If display size and viewing distance remain the same for both APS-C and FF images, they are no longer a variable and can be ignored.