Noob Depth of field question

[svguy]

Yes many different opinions. I guess the end result is what matters. I asked a couple local photog friends and one told me to back up a few feet, the other told me to close down the aperture and use more light.

It's crazy how just a couple feet too close to your subject, can ruin the photo. I need to be more mindful of this. I'm not saying this photo is ruined. The real subject here is the puppies, so I don't care as much about Morgan's eyes. But it it the point of it that I need to learn how to perfect this. I want to make sure I get consistent and when I'm shooting un-tethered, I don't want to sit down after the shoot and be disappointed with focus problems. DOF and focusing issues has been my biggest learning challenge.

When I first posted this question, I thought I was going to be flamed for asking such a NOOB question where the answer was going to be obvious. Thanks again for all the great support.

 

[MarshallG]

Actually there isn't an eye in the shot that's in focus. Use loop in your album to take a look.

Where was your focal point? Was your camera mounted or handheld?

All that said it's a nice shot.

I won't argue with that. I often take photos of puppies and they are always moving. Getting good focus is always a challenge. Lets just say Morgan's eyes are LESS in focus than the puppy's eyes. I usually use flexible spot focus and try to focus on a puppy eye. But in this shot, I need to be able to focus pretty much on any puppy and have enough depth of field to be sure to get everything in focus.

The DOF calculator is correct. The solution is to use a smaller aperture to get more DOF.

Yes.

That means that something else also needs to change if you want the same exposure value.

Sort of. While the statement is true, your next paragraph seems to indicate that when you said "exposure value" you actually meant image brightness. An exposure value is a number that indicates all possible combinations of aperture and shutter that will give the same exposure (amount of light hitting the sensor per unit area) from any given scene luminance. So if you narrow the aperture, the only thing that can (and must) change to give the same exposure value is the shutter speed. It must be slowed by the same number of stops the aperture was narrowed.

The smaller aperture reduces the lens's ability to capture enough light quickly, so you need to either increase the sensor's ability to capture light by raising the ISO

No. Raising the ISO does not increase the sensor's ability to capture light. The sensor's ability to capture light is fixed, regardless of ISO setting. All increasing ISO does is increase the brightness of an image produced from any given exposure, while possibly slightly reducing the effect of noise added by the camera. If you reduce the exposure by narrowing the aperture while leaving shutter and scene luminance unchanged, then raising ISO by the same number of stops as you narrowed the aperture will produce an image of the same brightness, but made with less light. Because it was made with less light, it will be noisier.

or give the lens/sensure more time to work by decreasing the shutter speed. Or both.

OP also had the option of increasing the scene luminance by increasing the power of his flash. By increasing the power, he can reduce his exposure value (by narrowing aperture) while maintaining the same exposure. That's because exposure is determined by the combination of aperture, shutter and scene luminance. *

Photography is all about balancing those three factors in such a way that they produce the result you want.

Well, actually there are four factors to consider: scene luminance, aperture, shutter and ISO. The first three determine the exposure. For a given camera, exposure determines the shot noise. Exposure plus ISO determine the image brightness.

Which results you care about determines which of the four factors you need to balance. If you care about image brightness but don't care about noise, then you can balance exposure against ISO. If you also care about noise, then you need to balance the three parameters of exposure (aperture, shutter and scene luminance).

*It should be noted that doubling the flash power only doubles the scene luminance when the flash is the only source of light in the scene. That does not appear to be the case in this instance. Therefore doubling the flash power in this case will not double the scene luminance, so doubling flash power will not be sufficient to balance a one stop narrowing of aperture. Since shutter is about as slow as one would want with wiggling puppies as a subject, increasing flash and ISO would appear to be the best choice.

Blah blah blah blah... this sort of linguistic legerdemain doesn't help people take better photographs. It's just a bunch of nonsense, really. I've done this since the 1970's. Of course you need to balance the lighting with shutter/aperture/ISO and not overexpose or underexpose.

But the effect of aperture changes with focal length and distance and you can only get an understanding of it with practice, practice, practice. You can't see the whole effect through the viewfinder and chimping only helps a little. You can quote me all the physics equations in the world but it won't make your shooting much better. Practice will.

Yes, photography and golf swings are all based on physics, but in practice we need practice.

 

[Gerry Winterbourne]

Actually there isn't an eye in the shot that's in focus. Use loop in your album to take a look.

Where was your focal point? Was your camera mounted or handheld?

All that said it's a nice shot.

I won't argue with that. I often take photos of puppies and they are always moving. Getting good focus is always a challenge. Lets just say Morgan's eyes are LESS in focus than the puppy's eyes. I usually use flexible spot focus and try to focus on a puppy eye. But in this shot, I need to be able to focus pretty much on any puppy and have enough depth of field to be sure to get everything in focus.

The DOF calculator is correct. The solution is to use a smaller aperture to get more DOF.

Yes.

That means that something else also needs to change if you want the same exposure value.

Sort of. While the statement is true, your next paragraph seems to indicate that when you said "exposure value" you actually meant image brightness. An exposure value is a number that indicates all possible combinations of aperture and shutter that will give the same exposure (amount of light hitting the sensor per unit area) from any given scene luminance. So if you narrow the aperture, the only thing that can (and must) change to give the same exposure value is the shutter speed. It must be slowed by the same number of stops the aperture was narrowed.

The smaller aperture reduces the lens's ability to capture enough light quickly, so you need to either increase the sensor's ability to capture light by raising the ISO

No. Raising the ISO does not increase the sensor's ability to capture light. The sensor's ability to capture light is fixed, regardless of ISO setting. All increasing ISO does is increase the brightness of an image produced from any given exposure, while possibly slightly reducing the effect of noise added by the camera. If you reduce the exposure by narrowing the aperture while leaving shutter and scene luminance unchanged, then raising ISO by the same number of stops as you narrowed the aperture will produce an image of the same brightness, but made with less light. Because it was made with less light, it will be noisier.

or give the lens/sensure more time to work by decreasing the shutter speed. Or both.

OP also had the option of increasing the scene luminance by increasing the power of his flash. By increasing the power, he can reduce his exposure value (by narrowing aperture) while maintaining the same exposure. That's because exposure is determined by the combination of aperture, shutter and scene luminance. *

Photography is all about balancing those three factors in such a way that they produce the result you want.

Well, actually there are four factors to consider: scene luminance, aperture, shutter and ISO. The first three determine the exposure. For a given camera, exposure determines the shot noise. Exposure plus ISO determine the image brightness.

Which results you care about determines which of the four factors you need to balance. If you care about image brightness but don't care about noise, then you can balance exposure against ISO. If you also care about noise, then you need to balance the three parameters of exposure (aperture, shutter and scene luminance).

*It should be noted that doubling the flash power only doubles the scene luminance when the flash is the only source of light in the scene. That does not appear to be the case in this instance. Therefore doubling the flash power in this case will not double the scene luminance, so doubling flash power will not be sufficient to balance a one stop narrowing of aperture. Since shutter is about as slow as one would want with wiggling puppies as a subject, increasing flash and ISO would appear to be the best choice.

Blah blah blah blah... this sort of linguistic legerdemain

If you are going to use long words it's a good idea to know what they mean. You have put more blah into those two words than appears in the rest of the thread.

doesn't help people take better photographs.

Linguistic legerdemain, if used, won't help anyone; but understanding what happens is always a help to an intelligent person.

It's just a bunch of nonsense, really.

Really? Please explain which part of this explanation is nonsensical. To be nonsensical it would have to be technically untrue - is it? If you think so, say where.

I've done this since the 1970's. Of course you need to balance the lighting with shutter/aperture/ISO and not overexpose or underexpose.

And how does one achieve that? By random trial and error for 40 years? Or by understanding the principles and then applying them?

But the effect of aperture changes with focal length and distance and you can only get an understanding of it with practice, practice, practice.

Not so. Understanding comes from knowledge; once the knowledge is gained practice helps improve output.

You can't see the whole effect through the viewfinder and chimping only helps a little.

Why mention this? It's a new topic irrelevant to anything else that's been written.

You can quote me all the physics equations in the world but it won't make your shooting much better. Practice will.

I'm not sure what you're trying to say here. It's clear that telling you something won't improve my or anyone else's shooting, but no one's trying to do that.

And, to repeat, that practice will be more effective if it's based on understanding and not just random variation.

Yes, photography and golf swings are all based on physics, but in practice we need practice.

To improve at reasonable speed we need both. No one here has said that practice isn't needed so I don't understand why you keep mentioning it over and over. Of course it's needed; but it is by no means all that is needed.

 

[RRowlett]

If you need DOF, stop 'er down. You could consult DOF tables, but I would bet that at f/16 you should have a couple feet of DOF with a 50-70 mm lens at that distance.. At f/6.3 or f/8 you might be on the cusp of having enough DOF. The trick would be to stop down, and focus on the closest element you want in focus. Exactly what (nose, eye, etc.) won't matter than much as long as you have enough DOF. Of course, you will have to battle with appropriate shutter speed and available lighting to prevent motion blur. Worst case, you might be able to increase iSO to keep shutter speeds in a good range, and hopefully keep adequate image quality.

If you want good subject isolation from the background and foreground, it gets more complicated, but the best idea would be to try to focus on an eye in the closest subject and then try several exposures at different apertures to see if you can catch one with just enough but not too much DOF. With digital, you don't have to worry about taking too many shots--just delete the ones that don't work.

 

[apertority]

A bit late here, but did a comparison with a DOF calculator to double the DOF.

Starting point: Distance 5ft / aperture f/7.1 / focal lenght 58mm = DOF 11 inch. Vertical FOV at focus point is 45 inch.

Step back to 7ft: (aperture f/7.1) = DOF 22 inch. --> Vertical FOV grows to 63 inch.

• Must crop nearly half of the pixels for original framing.

Shink aperture to f/14: (distance 5ft) = DOF 22 inch.

• Must quadruple the amount of light.

I would do a compromise and step 1ft back, stop down to f/10 and double the light.

 

[Pixel Pooper]

Shink aperture to f/14: (distance 5ft) = DOF 22 inch.

• Must quadruple the amount of light.

I would do a compromise and step 1ft back, stop down to f/10 and double the light.

You don't have to double the light, you can raise ISO by 1 stop instead. Remember that when you crop you are throwing away that extra light, which affects SNR the same as raising the ISO instead of adding light.

 

[MarshallG]

Actually there isn't an eye in the shot that's in focus. Use loop in your album to take a look.

Where was your focal point? Was your camera mounted or handheld?

All that said it's a nice shot.

I won't argue with that. I often take photos of puppies and they are always moving. Getting good focus is always a challenge. Lets just say Morgan's eyes are LESS in focus than the puppy's eyes. I usually use flexible spot focus and try to focus on a puppy eye. But in this shot, I need to be able to focus pretty much on any puppy and have enough depth of field to be sure to get everything in focus.

The DOF calculator is correct. The solution is to use a smaller aperture to get more DOF.

Yes.

That means that something else also needs to change if you want the same exposure value.

Sort of. While the statement is true, your next paragraph seems to indicate that when you said "exposure value" you actually meant image brightness. An exposure value is a number that indicates all possible combinations of aperture and shutter that will give the same exposure (amount of light hitting the sensor per unit area) from any given scene luminance. So if you narrow the aperture, the only thing that can (and must) change to give the same exposure value is the shutter speed. It must be slowed by the same number of stops the aperture was narrowed.

The smaller aperture reduces the lens's ability to capture enough light quickly, so you need to either increase the sensor's ability to capture light by raising the ISO

No. Raising the ISO does not increase the sensor's ability to capture light. The sensor's ability to capture light is fixed, regardless of ISO setting. All increasing ISO does is increase the brightness of an image produced from any given exposure, while possibly slightly reducing the effect of noise added by the camera. If you reduce the exposure by narrowing the aperture while leaving shutter and scene luminance unchanged, then raising ISO by the same number of stops as you narrowed the aperture will produce an image of the same brightness, but made with less light. Because it was made with less light, it will be noisier.

or give the lens/sensure more time to work by decreasing the shutter speed. Or both.

OP also had the option of increasing the scene luminance by increasing the power of his flash. By increasing the power, he can reduce his exposure value (by narrowing aperture) while maintaining the same exposure. That's because exposure is determined by the combination of aperture, shutter and scene luminance. *

Photography is all about balancing those three factors in such a way that they produce the result you want.

Well, actually there are four factors to consider: scene luminance, aperture, shutter and ISO. The first three determine the exposure. For a given camera, exposure determines the shot noise. Exposure plus ISO determine the image brightness.

Which results you care about determines which of the four factors you need to balance. If you care about image brightness but don't care about noise, then you can balance exposure against ISO. If you also care about noise, then you need to balance the three parameters of exposure (aperture, shutter and scene luminance).

*It should be noted that doubling the flash power only doubles the scene luminance when the flash is the only source of light in the scene. That does not appear to be the case in this instance. Therefore doubling the flash power in this case will not double the scene luminance, so doubling flash power will not be sufficient to balance a one stop narrowing of aperture. Since shutter is about as slow as one would want with wiggling puppies as a subject, increasing flash and ISO would appear to be the best choice.

Blah blah blah blah... this sort of linguistic legerdemain

If you are going to use long words it's a good idea to know what they mean. You have put more blah into those two words than appears in the rest of the thread.

doesn't help people take better photographs.

Linguistic legerdemain, if used, won't help anyone; but understanding what happens is always a help to an intelligent person.

It's just a bunch of nonsense, really.

Really? Please explain which part of this explanation is nonsensical. To be nonsensical it would have to be technically untrue - is it? If you think so, say where.

I've done this since the 1970's. Of course you need to balance the lighting with shutter/aperture/ISO and not overexpose or underexpose.

And how does one achieve that? By random trial and error for 40 years? Or by understanding the principles and then applying them?

But the effect of aperture changes with focal length and distance and you can only get an understanding of it with practice, practice, practice.

Not so. Understanding comes from knowledge; once the knowledge is gained practice helps improve output.

You can't see the whole effect through the viewfinder and chimping only helps a little.

Why mention this? It's a new topic irrelevant to anything else that's been written.

You can quote me all the physics equations in the world but it won't make your shooting much better. Practice will.

I'm not sure what you're trying to say here. It's clear that telling you something won't improve my or anyone else's shooting, but no one's trying to do that.

And, to repeat, that practice will be more effective if it's based on understanding and not just random variation.

Yes, photography and golf swings are all based on physics, but in practice we need practice.

To improve at reasonable speed we need both. No one here has said that practice isn't needed so I don't understand why you keep mentioning it over and over. Of course it's needed; but it is by no means all that is needed.

 

[apertority]

Shink aperture to f/14: (distance 5ft) = DOF 22 inch.

• Must quadruple the amount of light.

I would do a compromise and step 1ft back, stop down to f/10 and double the light.

You don't have to double the light, you can raise ISO by 1 stop instead. Remember that when you crop you are throwing away that extra light, which affects SNR the same as raising the ISO instead of adding light.

Thank you for pointing this out!

Totally forgot the ISO from the equation.

This was a good question. Learned a few new things about photography.

 

[antoineb]

(1) too small apertures rob detail because of light diffraction. Don't go smaller than about f8. Not sure which camera you are using but if a DSLR that offers AF fine-tune, then fine-tune the AF.

(2) Google "DOF calculator" and you'll find a ton of them. Just type it your shooting parameters and you can play.

I know this "photography 101" question has been asked 1000 times but I can't seem to find the best solution here.
1/80
F/7.1
ISO 200
51mm
lens about 5 feet from subject

Notice the pups are sharp but I missed her eyes slightly.

I run into these situations where I want to fill the frame with my subject for best use of available mega pixles. If I back up and stay at 51mm, I know I'll have a better DOF, but I'll be using less mega pixels after cropping, as I won't be filling the frame with the subject.

My question is, If I back up a few feet and then go to 70mm, do I have a better DOF? Or does zooming into 70mm (to fill the frame) cancel out the better dof? According to a DOF calculator, it pretty much cancels out.

What do you do in a situation like this? Just back up and then crop? Or go to F/10 and use more light? My speed lite was already at 1/2 power.

Thanks for the help.

Tom

 

[Gerry Winterbourne]

Actually there isn't an eye in the shot that's in focus. Use loop in your album to take a look.

Where was your focal point? Was your camera mounted or handheld?

All that said it's a nice shot.

I won't argue with that. I often take photos of puppies and they are always moving. Getting good focus is always a challenge. Lets just say Morgan's eyes are LESS in focus than the puppy's eyes. I usually use flexible spot focus and try to focus on a puppy eye. But in this shot, I need to be able to focus pretty much on any puppy and have enough depth of field to be sure to get everything in focus.

The DOF calculator is correct. The solution is to use a smaller aperture to get more DOF.

Yes.

That means that something else also needs to change if you want the same exposure value.

Sort of. While the statement is true, your next paragraph seems to indicate that when you said "exposure value" you actually meant image brightness. An exposure value is a number that indicates all possible combinations of aperture and shutter that will give the same exposure (amount of light hitting the sensor per unit area) from any given scene luminance. So if you narrow the aperture, the only thing that can (and must) change to give the same exposure value is the shutter speed. It must be slowed by the same number of stops the aperture was narrowed.

The smaller aperture reduces the lens's ability to capture enough light quickly, so you need to either increase the sensor's ability to capture light by raising the ISO

No. Raising the ISO does not increase the sensor's ability to capture light. The sensor's ability to capture light is fixed, regardless of ISO setting. All increasing ISO does is increase the brightness of an image produced from any given exposure, while possibly slightly reducing the effect of noise added by the camera. If you reduce the exposure by narrowing the aperture while leaving shutter and scene luminance unchanged, then raising ISO by the same number of stops as you narrowed the aperture will produce an image of the same brightness, but made with less light. Because it was made with less light, it will be noisier.

or give the lens/sensure more time to work by decreasing the shutter speed. Or both.

OP also had the option of increasing the scene luminance by increasing the power of his flash. By increasing the power, he can reduce his exposure value (by narrowing aperture) while maintaining the same exposure. That's because exposure is determined by the combination of aperture, shutter and scene luminance. *

Photography is all about balancing those three factors in such a way that they produce the result you want.

Well, actually there are four factors to consider: scene luminance, aperture, shutter and ISO. The first three determine the exposure. For a given camera, exposure determines the shot noise. Exposure plus ISO determine the image brightness.

Which results you care about determines which of the four factors you need to balance. If you care about image brightness but don't care about noise, then you can balance exposure against ISO. If you also care about noise, then you need to balance the three parameters of exposure (aperture, shutter and scene luminance).

*It should be noted that doubling the flash power only doubles the scene luminance when the flash is the only source of light in the scene. That does not appear to be the case in this instance. Therefore doubling the flash power in this case will not double the scene luminance, so doubling flash power will not be sufficient to balance a one stop narrowing of aperture. Since shutter is about as slow as one would want with wiggling puppies as a subject, increasing flash and ISO would appear to be the best choice.

Blah blah blah blah... this sort of linguistic legerdemain

If you are going to use long words it's a good idea to know what they mean. You have put more blah into those two words than appears in the rest of the thread.

doesn't help people take better photographs.

Linguistic legerdemain, if used, won't help anyone; but understanding what happens is always a help to an intelligent person.

It's just a bunch of nonsense, really.

Really? Please explain which part of this explanation is nonsensical. To be nonsensical it would have to be technically untrue - is it? If you think so, say where.

I've done this since the 1970's. Of course you need to balance the lighting with shutter/aperture/ISO and not overexpose or underexpose.

And how does one achieve that? By random trial and error for 40 years? Or by understanding the principles and then applying them?

But the effect of aperture changes with focal length and distance and you can only get an understanding of it with practice, practice, practice.

Not so. Understanding comes from knowledge; once the knowledge is gained practice helps improve output.

You can't see the whole effect through the viewfinder and chimping only helps a little.

Why mention this? It's a new topic irrelevant to anything else that's been written.

You can quote me all the physics equations in the world but it won't make your shooting much better. Practice will.

I'm not sure what you're trying to say here. It's clear that telling you something won't improve my or anyone else's shooting, but no one's trying to do that.

And, to repeat, that practice will be more effective if it's based on understanding and not just random variation.

Yes, photography and golf swings are all based on physics, but in practice we need practice.

To improve at reasonable speed we need both. No one here has said that practice isn't needed so I don't understand why you keep mentioning it over and over. Of course it's needed; but it is by no means all that is needed.

To be honest with you, I've read these nerdy posts here many times, and I don't see how they help.

Two things here. "Nerdy" is a term of denigration which says more about your attitude to knowledge than it does about the information being passed on.

Technical information about any technique (photography or anything else) helps one understand how to make the most of that technique. Beginners - almost by definition - start from a basis of ignorance. They can only learn and improve their technique by learning about it.

That learning can be acquired in two ways: a tedious process of trial and error or by reading. If you don't understand that it's either because you've forgotten that you had to learn things 40 years ago or that there are things that 40 years of trial and error haven't taught you.

Quibbling over the definition of EV or saying that changing ISO doesn't change exposure... these are definitions.

And this is a case in point. I agree that a mere definition is academic as such (and, incidentally, I think that the 100 year old definition of exposure is out-moded for digital cameras) but ...

Understanding the distinction of whether EV refers to the ISO in use or not doesn't help you take better photographs.

... knowing that the noise in a photo increases as exposure is reduced is important. Thinking that ISO is interchangeable with aperture or shutter speed can lead to unnecessary noise is a photo. Knowing that can help with taking better photos.

Sorry, it just doesn't. It just lets you win an argument.

So, sorry, but what you say is wrong.

Then he goes on to say that adding artificial light is a fourth exposure control, which is somewhat true but it doesn't make the so-called exposure triangle wrong.

Here's the root of the problem. The exposure triangle brings ISO into the settings used, which affects the brightness of the image but not its exposure as currently (for over 100 years) defined. I have no problem with that in principle but it does mean that the question of noise needs full consideration.

The exposure triangle as commonly used isn't "wring" except by definition but it is inadequate. Mentioning light doesn't alter the rightness or adequacy of the exposure triangle. What it does is try to counter the inadequacy.

But I feel that using flash as an exposure control is usually not a very good application of flash. It works much better, in my opinion, as a light modifier which changes the character of your photograph.

How one uses the various things at one's disposal is obviously very important. But it's a different topic from what's under discussion here.

I'm sorry if I ruffled your feathers. I didn't mean to

I'm sure you didn't ...

but I'm still kinda sick of these sorts of interjections in which someone makes somebody else sound wrong

... and I'd agree if the original statement was correct and the intervention made the truth appear untrue; but not when the intervention corrects something that was incorrect ...

by adding so much complexity to the thread that the original poster gets confused with information

... what makes you think that the OP is incapable of grasping a few simple facts? What's confusing about the fact that lack of light can cause unwanted image noise and that increasing ISO doesn't add light?

And that increasing ISO will increase the brightness of the picture so there's a choice - add light and alter the nature of the picture; increase ISO and risk noise. Once the choice is explained the user can make an informed decision.

which I believe does little to improve your photography.

There's no guarantee that knowledge improves anything. There are aspects of photography that are unaffected by technical knowledge. But despite 50 years experience of film photography my results improved after learning about how digital photography works.

As far as your belief goes - that knowing these things does little to improve my photography - it is demonstrably wrong. And in the general case a little improvement is surely worth having.

 

[RRowlett]

(1) too small apertures rob detail because of light diffraction. Don't go smaller than about f8. Not sure which camera you are using but if a DSLR that offers AF fine-tune, then fine-tune the AF

The concern about using small apertures is overblown. Photographers often use hyperfocal focusing at small apertures to create images with sharpness throughout. The effects of diffraction may be insignificant compared to out of focus elements due to lack of DOF. Use the aperture needed to achieve the desired goal. If there is not enough DOF at f/8 you have to do something else. The beauty of digital captures is that you can try different approaches and see what works without wasting anything but a little time. Try different apertures and see what aperture provides adequate DOF and subject isolation.

 

[Gerry Winterbourne]

(1) too small apertures rob detail because of light diffraction. Don't go smaller than about f8. Not sure which camera you are using but if a DSLR that offers AF fine-tune, then fine-tune the AF

The concern about using small apertures is overblown.

Is it? The answer depends very largely on the size of sensor.

The advice to stick to f/8 is unduly pessimistic for the OP's camera, which is full frame. The direct effect of diffraction doesn't really show there until about f/16. For APS-C cameras such as the ones in your gear list f/11 is usually the critical aperture.

Note that I said "direct" - there are the indirect effects of requiring either a longer shutter speed or higher ISO, both of which can - although they don't always - cause loss of sharpness through motion blur or noise.

Photographers often use hyperfocal focusing at small apertures to create images with sharpness throughout.

And often they lose sharpness throughout if they stop down too far.

The effects of diffraction may be insignificant compared to out of focus elements due to lack of DOF.

Diffraction reduces resolution across the frame. The limits of DOF are set by loss of resolution. There is a point at which the two balance - it is the critical f-number I mentioned above. If you stop down too far diffraction increases the size of the circle of confusion and DOF actually shrinks.

This link allows you to calculate the effect of diffraction on DOF. Unfortunately it shows the effect only in the graphical output - look at the way the blue line moves when diffraction is included http://www.tawbaware.com/maxlyons/calc.htm

 

[MarshallG]

There's no guarantee that knowledge improves anything. There are aspects of photography that are unaffected by technical knowledge. But despite 50 years experience of film photography my results improved after learning about how digital photography works.

As far as your belief goes - that knowing these things does little to improve my photography - it is demonstrably wrong. And in the general case a little improvement is surely worth having.

Gerry,

I appreciate you and I've gotten to know you over the years on this board, but the OP wants to know why a girl's eyes were out of focus. When someone told him that closing the aperture would mean increasing ISO, it wasn't all that useful for someone else to "make him wrong" and dive into a diatribe about how ISO isn't exposure even though it's exposure triangle but it isn't really exposure. Sorry; it just derailed the conversation. The photo is correctly exposed. The OP just wanted to know why his subject's eyes weren't razor sharp.

To be honest, his question is a really good one. I seriously doubt the suggestions made that dropping the aperture from 7.1 to 8 would fix it. I think the answer has three parts:

1) If you don't want to use flash or add light, then this exposure is about as good as it can be. i'd move the ISO to 400 to close the aperture down one more stop to about f/11, but that's it. After f/11, diffraction would probably soften the image anyway, and it may even do so at f/11 with that lens.

2) AF on the girl's eyes, not the dogs

3) AF isn't perfect; shoot many times to get her eyes in perfectly sharp focus

That's what I think. What do you think?

 

[Gerry Winterbourne]

There's no guarantee that knowledge improves anything. There are aspects of photography that are unaffected by technical knowledge. But despite 50 years experience of film photography my results improved after learning about how digital photography works.

As far as your belief goes - that knowing these things does little to improve my photography - it is demonstrably wrong. And in the general case a little improvement is surely worth having.

I appreciate you and I've gotten to know you over the years on this board, but the OP wants to know why a girl's eyes were out of focus. When someone told him that closing the aperture would mean increasing ISO,

But that advice came with the statement " increase the sensor's ability to capture light by raising the ISO" ...

it wasn't all that useful for someone else to "make him wrong"

... and that is wrong. If the advice had been simply to increase ISO it would have been OK, albeit without a warning about noise. If it had been accompanied by a warning about noise it would have been OK.

But the problem here (and it's quite common) is that advice that's OK in itself is accompanied by errors of fact. Two people are affected by this: more important, the beginner asking a question who is fed false information; but also the person giving the false information. The second person should, I think, be told of the mistake in the hope that he won't tell some other beginner the same false information (and, as a by-product, may also learn something).

and dive into a diatribe about how ISO isn't exposure even though it's exposure triangle but it isn't really exposure. Sorry; it just derailed the conversation. The photo is correctly exposed. The OP just wanted to know why his subject's eyes weren't razor sharp.

I don't think it derailed anything. The OP asked a question and got several direct responses with a range of answers to what he actually asked. One of them not only answered the question but injected mistaken advice. It was that injection that derailed the thread: without it the correction wouldn't have been needed and we wouldn't be having this discussion.

To be honest, his question is a really good one. I seriously doubt the suggestions made that dropping the aperture from 7.1 to 8 would fix it. I think the answer has three parts:

These suggestions aren't exactly the same as the others but there is overlap. They add to the range of options for the OP to try and/or choose from. Importantly, and pertinently here, they don't include errors.

1) If you don't want to use flash or add light, then this exposure is about as good as it can be. i'd move the ISO to 400 to close the aperture down one more stop to about f/11, but that's it. After f/11, diffraction would probably soften the image anyway, and it may even do so at f/11 with that lens.

2) AF on the girl's eyes, not the dogs

3) AF isn't perfect; shoot many times to get her eyes in perfectly sharp focus

That's what I think. What do you think?

My first thoughts were expressed here https://www.dpreview.com/forums/post/59854019

 

[antoineb]

Like you say: no need for theory.

Anyone can take controlled shots (camera on tripod, timer etc) and check from what Aperture, for their taste, some detail starts getting lost.

It's not "overblown" as you claim. Just one of many examples, Nikon's technical manual for the D810 recommends to not go smaller than f5.6 for best detail. On an APS-C camera it is best not to go smaller than about f8.

But again: anyone can do a series of comparison shots and decide for themselves.

(1) too small apertures rob detail because of light diffraction. Don't go smaller than about f8. Not sure which camera you are using but if a DSLR that offers AF fine-tune, then fine-tune the AF

The concern about using small apertures is overblown. Photographers often use hyperfocal focusing at small apertures to create images with sharpness throughout. The effects of diffraction may be insignificant compared to out of focus elements due to lack of DOF. Use the aperture needed to achieve the desired goal. If there is not enough DOF at f/8 you have to do something else. The beauty of digital captures is that you can try different approaches and see what works without wasting anything but a little time. Try different apertures and see what aperture provides adequate DOF and subject isolation.