Hello everyone. I own the rf 100-400 lens. I like it. So light and small yet iq is good. Fot the extra reach should I buy the 1.4 extender and use it with the 100-400 or get the 600 f11 ? Has anyone comperad the af speed and iq of the two set ups? I have an R7 btw.
-
Welcome to the new forums! Please read this first. For known issues we are working to resolve, click here.
Rf 100-400 plus 1.4 Tc or Rf 600 F11
- Thread starter OlcayK
- Start date
And that's the reason I only tested it with a chart now. Because once I processed actual images from the RF100-400 on the R7, I could see the diffraction blur would make the TC useless, as expected based on the diffraction theory. But I decided to do a confirming test to make sure my intuition and subjective experience matched observable reality.
Shooting experience can be very expensive, and while testing isn't free, it can be time well spent, especially if it keeps you from disappointing a client.
Thank you for your answers Bigger and Steve! Very interesting considerations.
Also thank you Alistair for pointing out not everything translates from theory to actually using it. I fully agree with you, but I have to say I have respect for people who take the time to test setups and combos to help answering the question from OP.
I would like to add that I agree the IQ will not improve in any way with a TC. But even without a TC the IQ would be poor when shooting at a fair distance. For me personally I only take those photo's to identify birds when I can't identify them in the field.
Jeroen
Alastair Norcross
Forum Pro
Well, as I said, theory is one thing, but often practice is very different. What I want to know is whether using a 1.4X converter with the RF100-1400 on my R7 will be beneficial for me, given what I shoot, how I shoot it, and how I process and display the results. So I just did a quick comparison test, shooting a tree at a distance that represents the close end of the range I actually use that lens (with or without extender) for. I then processed the pictures the way I process all my pictures (I have a preset I use with DXO Photolab). And then I cropped both images a reasonable amount, which is what I do with most of the shots I take with that lens. I cropped both to give the same field of view, which meant cropping the 400mm shot more than the 560mm shot, of course. I then exported both images as JPEGs downsized to 2000 pixels on the long side, which is how I display most of my images. Viewing those JPEGs on a modern monitor is roughly equivalent to looking at a print that's anywhere from 10 inches across to 20 inches across, depending on your screen resolution. What I discovered is that yes, you do get a benefit from using the extender. Here are the downsized images, first the whole frame:
Focus is on the dark knot at the center
And here are the two crops, framed as close to each other as I could without spending even longer on this than I have already:
To my eye, the 560mm shot has a bit more detail. It's not a huge difference, but it's enough to make it worth using the extender, especially because you do get the AF advantage with having a closer in field of view.
When making decisions about this, there's really no substitute for actual experience, and experience that's relevant to what you're going to be using the lens for. Talk of airy disks and extinction resolution is all very well, but it's often not just confusing, but actually misleading. For all I know, the lens + extender combination wouldn't be advantageous for other processing plus display choices, but the only way to know is to actually try it.
--
“When I die, I want to go peacefully in my sleep like my grandfather. Not screaming in terror, like the passengers in his car.” Jack Handey
Alastair
http://anorcross.smugmug.com
Equipment in profile
Last edited:
Thank you for testing it! It indeed looks like the dark knot has more detail with the TC.Well, as I said, theory is one thing, but often practice is very different. What I want to know is whether using a 1.4X converter with the RF100-1400 on my R7 will be beneficial for me, given what I shoot, how I shoot it, and how I process and display the results. So I just did a quick comparison test, shooting a tree at a distance that represents the close end of the range I actually use that lens (with or without extender) for. I then processed the pictures the way I process all my pictures (I have a preset I use with DXO Photolab). And then I cropped both images a reasonable amount, which is what I do with most of the shots I take with that lens. I cropped both to give the same field of view, which meant cropping the 400mm shot more than the 560mm shot, of course. I then exported both images as JPEGs downsized to 2000 pixels on the long side, which is how I display most of my images. Viewing those JPEGs on a modern monitor is roughly equivalent to looking at a print that's anywhere from 10 inches across to 20 inches across, depending on your screen resolution. What I discovered is that yes, you do get a benefit from using the extender. Here are the downsized images, first the whole frame:
Focus is on the dark knot at the center
And here are the two crops, framed as close to each other as I could without spending even longer on this than I have already:
To my eye, the 560mm shot has a bit more detail. It's not a huge difference, but it's enough to make it worth using the extender, especially because you do get the AF advantage with having a closer in field of view.
When making decisions about this, there's really no substitute for actual experience, and experience that's relevant to what you're going to be using the lens for. Talk of airy disks and extinction resolution is all very well, but it's often not just confusing, but actually misleading. For all I know, the lens + extender combination wouldn't be advantageous for other processing plus display choices, but the only way to know is to actually try it.
The vine Bob is asking about could be moving from wind.
Jeroen
Alastair Norcross
Forum Pro
Hi Bob, yes the vine in the 400mm shot is less out of focus than it is in the 560mm shot. That's because it moved between shots. If you look carefully at the spots on the twig behind it, you'll see that it is closer to the dark knot, which was the plane of focus, in the 400mm shot. It's also possible that it is moving in this shot, and motion blur is a factor. I don't know whether 1/640 would have been fast enough to freeze that. Also, and I don't know whether this is big enough to be visible here, the DOF for 400mm at F8 is slightly larger than for 560mm at F11 (according to online calculators). Given that the shots were equalized in size, I don't know whether that difference would show up, so the slight difference in position probably explains all the difference we're seeing here.Thanks for your efforts.
I'm a little confused, though. I look at a smaller crop of each.
The shot without the TC is at the left.
I think I see more detail in the vine, left of center.
Do you agree?
--
“When I die, I want to go peacefully in my sleep like my grandfather. Not screaming in terror, like the passengers in his car.” Jack Handey
Alastair
http://anorcross.smugmug.com
Equipment in profile
Last edited:
Dave C 150
Forum Enthusiast
Thanks, most useful. They look identical to me, most certainly not £500 better anyway ;-)Thank you for testing it! It indeed looks like the dark knot has more detail with the TC.Well, as I said, theory is one thing, but often practice is very different. What I want to know is whether using a 1.4X converter with the RF100-1400 on my R7 will be beneficial for me, given what I shoot, how I shoot it, and how I process and display the results. So I just did a quick comparison test, shooting a tree at a distance that represents the close end of the range I actually use that lens (with or without extender) for. I then processed the pictures the way I process all my pictures (I have a preset I use with DXO Photolab). And then I cropped both images a reasonable amount, which is what I do with most of the shots I take with that lens. I cropped both to give the same field of view, which meant cropping the 400mm shot more than the 560mm shot, of course. I then exported both images as JPEGs downsized to 2000 pixels on the long side, which is how I display most of my images. Viewing those JPEGs on a modern monitor is roughly equivalent to looking at a print that's anywhere from 10 inches across to 20 inches across, depending on your screen resolution. What I discovered is that yes, you do get a benefit from using the extender. Here are the downsized images, first the whole frame:
Focus is on the dark knot at the center
And here are the two crops, framed as close to each other as I could without spending even longer on this than I have already:
To my eye, the 560mm shot has a bit more detail. It's not a huge difference, but it's enough to make it worth using the extender, especially because you do get the AF advantage with having a closer in field of view.
When making decisions about this, there's really no substitute for actual experience, and experience that's relevant to what you're going to be using the lens for. Talk of airy disks and extinction resolution is all very well, but it's often not just confusing, but actually misleading. For all I know, the lens + extender combination wouldn't be advantageous for other processing plus display choices, but the only way to know is to actually try it.
The vine Bob is asking about could be moving from wind.
Jeroen
--
The DoF of the base lens does not change when you add a TC and then crop to the same subject dimensions. DoF calculators are based on a circle of confusion on a given print size viewing distance and visual acuity, typically 8x10" @ 10" with 0.2mm, but that assumes printing the full sensor area.Hi Bob, yes the vine in the 400mm shot is less out of focus than it is in the 560mm shot. That's because it moved between shots. If you look carefully at the spots on the twig behind it, you'll see that it is closer to the dark knot, which was the plane of focus, in the 400mm shot. It's also possible that it is moving in this shot, and motion blur is a factor. I don't know whether 1/640 would have been fast enough to freeze that. Also, and I don't know whether this is big enough to be visible here, the DOF for 400mm at F8 is slightly larger than for 560mm at F11 (according to online calculators). Given that the shots were equalized in size, I don't know whether that difference would show up, so the slight difference in position probably explains all the difference we're seeing here.Thanks for your efforts.
I'm a little confused, though. I look at a smaller crop of each.
The shot without the TC is at the left.
I think I see more detail in the vine, left of center.
Do you agree?
I don't see any significant difference, and certainly not $500 worth. So if your recommendation to the OP is to purchase an RF 1.4x TC to put between the R7 and the RF100-400, I still do not think that is good advice.
It is a good idea to cross-test to check your assumptions and conclusions as you suggest. That's the lesson from the Hubble Telescope mirror fiasco. But the real lesson from that is to be careful how you interpret conflicting results. The mirror flaw was detected in some tests, but this was dismissed because the more precise but inaccurate test was relied upon.
Alastair Norcross
Forum Pro
And you’d probably get the same similarity with a shot from the 800 and an upsized crop from the 600. As has been pointed out, there are other advantages to getting a narrower field of view in camera, as opposed to cropping and uprezzing in post. That’s why Canon gives you crop mode in camera too. For those who want to justify the decision not to use an extender, it’s easy to do it, and it’s fine. You don’t need to declare categorically that there are no benefits or reasons to use extenders, with this or any other lens. Those of us who do use them know that’s false. Do I expect to get at least $499 worth out of this extender in my 100-400? Easily, yes, especially given how much I plan to use it. Others are free to make a different value judgment for themselves. You don’t have to justify yourself to us by saying things that aren’t true.Thanks, most useful. They look identical to me, most certainly not £500 better anyway ;-)Thank you for testing it! It indeed looks like the dark knot has more detail with the TC.Well, as I said, theory is one thing, but often practice is very different. What I want to know is whether using a 1.4X converter with the RF100-1400 on my R7 will be beneficial for me, given what I shoot, how I shoot it, and how I process and display the results. So I just did a quick comparison test, shooting a tree at a distance that represents the close end of the range I actually use that lens (with or without extender) for. I then processed the pictures the way I process all my pictures (I have a preset I use with DXO Photolab). And then I cropped both images a reasonable amount, which is what I do with most of the shots I take with that lens. I cropped both to give the same field of view, which meant cropping the 400mm shot more than the 560mm shot, of course. I then exported both images as JPEGs downsized to 2000 pixels on the long side, which is how I display most of my images. Viewing those JPEGs on a modern monitor is roughly equivalent to looking at a print that's anywhere from 10 inches across to 20 inches across, depending on your screen resolution. What I discovered is that yes, you do get a benefit from using the extender. Here are the downsized images, first the whole frame:
Focus is on the dark knot at the center
And here are the two crops, framed as close to each other as I could without spending even longer on this than I have already:
To my eye, the 560mm shot has a bit more detail. It's not a huge difference, but it's enough to make it worth using the extender, especially because you do get the AF advantage with having a closer in field of view.
When making decisions about this, there's really no substitute for actual experience, and experience that's relevant to what you're going to be using the lens for. Talk of airy disks and extinction resolution is all very well, but it's often not just confusing, but actually misleading. For all I know, the lens + extender combination wouldn't be advantageous for other processing plus display choices, but the only way to know is to actually try it.
The vine Bob is asking about could be moving from wind.
Jeroen
--
https://www.flickr.com/photos/dcweather/
--
“When I die, I want to go peacefully in my sleep like my grandfather. Not screaming in terror, like the passengers in his car.” Jack Handey
Alastair
anorcross
Keen hobbyist since teaching myself film photography as a teenager in the 70s, using manual SLRs and black and white film. Love photographing people and animals.
anorcross.smugmug.com
I really thank everyone who contributed to the topic. You have put a lot of effort to make things clear. I wasn't expecting that much response. For now, I guess I'll skip the extender and save up for the rf 100-500 or wait for a miracle that canon lets 3rd party lenses. Cheers.
No an upsize from the 600/11 will not be comparable to the 800/11, because the latter has a much larger entrance aperture (600/11=55mm vs. 800/11=73mm). Also, I don't think the R7 has a crop mode like the FF bodies, as it is already cropped (if it does, I have not found it).And you’d probably get the same similarity with a shot from the 800 and an upsized crop from the 600. As has been pointed out, there are other advantages to getting a narrower field of view in camera, as opposed to cropping and uprezzing in post. That’s why Canon gives you crop mode in camera too. For those who want to justify the decision not to use an extender, it’s easy to do it, and it’s fine. You don’t need to declare categorically that there are no benefits or reasons to use extenders, with this or any other lens. Those of us who do use them know that’s false. Do I expect to get at least $499 worth out of this extender in my 100-400? Easily, yes, especially given how much I plan to use it. Others are free to make a different value judgment for themselves. You don’t have to justify yourself to us by saying things that aren’t true.Thanks, most useful. They look identical to me, most certainly not £500 better anyway ;-)Thank you for testing it! It indeed looks like the dark knot has more detail with the TC.Well, as I said, theory is one thing, but often practice is very different. What I want to know is whether using a 1.4X converter with the RF100-1400 on my R7 will be beneficial for me, given what I shoot, how I shoot it, and how I process and display the results. So I just did a quick comparison test, shooting a tree at a distance that represents the close end of the range I actually use that lens (with or without extender) for. I then processed the pictures the way I process all my pictures (I have a preset I use with DXO Photolab). And then I cropped both images a reasonable amount, which is what I do with most of the shots I take with that lens. I cropped both to give the same field of view, which meant cropping the 400mm shot more than the 560mm shot, of course. I then exported both images as JPEGs downsized to 2000 pixels on the long side, which is how I display most of my images. Viewing those JPEGs on a modern monitor is roughly equivalent to looking at a print that's anywhere from 10 inches across to 20 inches across, depending on your screen resolution. What I discovered is that yes, you do get a benefit from using the extender. Here are the downsized images, first the whole frame:
Focus is on the dark knot at the center
And here are the two crops, framed as close to each other as I could without spending even longer on this than I have already:
To my eye, the 560mm shot has a bit more detail. It's not a huge difference, but it's enough to make it worth using the extender, especially because you do get the AF advantage with having a closer in field of view.
When making decisions about this, there's really no substitute for actual experience, and experience that's relevant to what you're going to be using the lens for. Talk of airy disks and extinction resolution is all very well, but it's often not just confusing, but actually misleading. For all I know, the lens + extender combination wouldn't be advantageous for other processing plus display choices, but the only way to know is to actually try it.
The vine Bob is asking about could be moving from wind.
Jeroen
The main advantage to having a narrower field of view without added resolution is viewfinder (or display) magnification. That may make it easier to see a small subject, but then you would be cropping heavily. And it comes at the cost of cropping out part of a larger and/or moving subject, such as the wingtip of a BiF. So I would not recommend using a TC unless there was some real expected benefit.
Dave C 150
Forum Enthusiast
I'm quite happy for others to have other views and their own reasons for getting a TC. I'm just stating it as being useful for my own personal decision.No an upsize from the 600/11 will not be comparable to the 800/11, because the latter has a much larger entrance aperture (600/11=55mm vs. 800/11=73mm). Also, I don't think the R7 has a crop mode like the FF bodies, as it is already cropped (if it does, I have not found it).And you’d probably get the same similarity with a shot from the 800 and an upsized crop from the 600. As has been pointed out, there are other advantages to getting a narrower field of view in camera, as opposed to cropping and uprezzing in post. That’s why Canon gives you crop mode in camera too. For those who want to justify the decision not to use an extender, it’s easy to do it, and it’s fine. You don’t need to declare categorically that there are no benefits or reasons to use extenders, with this or any other lens. Those of us who do use them know that’s false. Do I expect to get at least $499 worth out of this extender in my 100-400? Easily, yes, especially given how much I plan to use it. Others are free to make a different value judgment for themselves. You don’t have to justify yourself to us by saying things that aren’t true.Thanks, most useful. They look identical to me, most certainly not £500 better anyway ;-)Thank you for testing it! It indeed looks like the dark knot has more detail with the TC.Well, as I said, theory is one thing, but often practice is very different. What I want to know is whether using a 1.4X converter with the RF100-1400 on my R7 will be beneficial for me, given what I shoot, how I shoot it, and how I process and display the results. So I just did a quick comparison test, shooting a tree at a distance that represents the close end of the range I actually use that lens (with or without extender) for. I then processed the pictures the way I process all my pictures (I have a preset I use with DXO Photolab). And then I cropped both images a reasonable amount, which is what I do with most of the shots I take with that lens. I cropped both to give the same field of view, which meant cropping the 400mm shot more than the 560mm shot, of course. I then exported both images as JPEGs downsized to 2000 pixels on the long side, which is how I display most of my images. Viewing those JPEGs on a modern monitor is roughly equivalent to looking at a print that's anywhere from 10 inches across to 20 inches across, depending on your screen resolution. What I discovered is that yes, you do get a benefit from using the extender. Here are the downsized images, first the whole frame:
Focus is on the dark knot at the center
And here are the two crops, framed as close to each other as I could without spending even longer on this than I have already:
To my eye, the 560mm shot has a bit more detail. It's not a huge difference, but it's enough to make it worth using the extender, especially because you do get the AF advantage with having a closer in field of view.
When making decisions about this, there's really no substitute for actual experience, and experience that's relevant to what you're going to be using the lens for. Talk of airy disks and extinction resolution is all very well, but it's often not just confusing, but actually misleading. For all I know, the lens + extender combination wouldn't be advantageous for other processing plus display choices, but the only way to know is to actually try it.
The vine Bob is asking about could be moving from wind.
Jeroen
The main advantage to having a narrower field of view without added resolution is viewfinder (or display) magnification. That may make it easier to see a small subject, but then you would be cropping heavily. And it comes at the cost of cropping out part of a larger and/or moving subject, such as the wingtip of a BiF. So I would not recommend using a TC unless there was some real expected benefit.
--
I considered motion, but I presumed that the exposure was sufficient to freeze the object. could the vine have moved that much in focus between shots? Judging from the lack of change in the shadows, I assume that the delay between shots wasn't long.Hi Bob, yes the vine in the 400mm shot is less out of focus than it is in the 560mm shot. That's because it moved between shots. If you look carefully at the spots on the twig behind it, you'll see that it is closer to the dark knot, which was the plane of focus, in the 400mm shot. It's also possible that it is moving in this shot, and motion blur is a factor. I don't know whether 1/640 would have been fast enough to freeze that. Also, and I don't know whether this is big enough to be visible here, the DOF for 400mm at F8 is slightly larger than for 560mm at F11 (according to online calculators). Given that the shots were equalized in size, I don't know whether that difference would show up, so the slight difference in position probably explains all the difference we're seeing here.Thanks for your efforts.
I'm a little confused, though. I look at a smaller crop of each.
The shot without the TC is at the left.
I think I see more detail in the vine, left of center.
Do you agree?
If the DOF calculator is showing a difference between the 400 f/8 with and without the 1.4X TC, I presume that it's using a definition based on image plane blur rather than blur at the object. (Adding a TC doesn't change that.) I might prefer the second criterion.
Adding my 2 cents, I did a couple tests with the R7 + RF 100-400 with and without 1.4 TC. Shot in cRAW, manual 1/400s AutoISO. Exported with DXO Photolab 6 Deeprime (all other settings by default). All photos are 1:1 crops and the focus point is at the center of the image. I took several bursts Electronic Shutter 30fps and selected the sharpest of each photo.
1st test: difference in detail obtained with/without the teleconverter - maximum zoom
Roof of house aprox 500m away, 400mm F8 without TC (upscaled *1.4 in faststone image viewer lanczos3 to equalize pixel size, then 1:1 crop) vs 560mm F11 with 1.4 TC
400mm F8 without TC (upscaled *1.4 in faststone image viewer lanczos3 to equalize pixel size, then 1:1 crop)
560mm F11 with 1.4 TC
(notice the difference in detail in the AC unit and the solar panels)
2nd test: difference in detail obtained at same focal length (400mm) with/without teleconverter (F8 and F11) vs aprox 400mm (397mm as per the camera) F11 with the TC.
Communications tower aprox 1500m away (1 mile), 400mm F8 without TC, 400mm F11 also without TC (to isolate the diffraction effect) and 397mm F11 with TC. No upscales or downscales, only 1:1 crops.
400mm F8 without TC
400mm F11 also without TC
397mm F11 with TC
1st test: difference in detail obtained with/without the teleconverter - maximum zoom
Roof of house aprox 500m away, 400mm F8 without TC (upscaled *1.4 in faststone image viewer lanczos3 to equalize pixel size, then 1:1 crop) vs 560mm F11 with 1.4 TC
400mm F8 without TC (upscaled *1.4 in faststone image viewer lanczos3 to equalize pixel size, then 1:1 crop)
560mm F11 with 1.4 TC
(notice the difference in detail in the AC unit and the solar panels)
2nd test: difference in detail obtained at same focal length (400mm) with/without teleconverter (F8 and F11) vs aprox 400mm (397mm as per the camera) F11 with the TC.
Communications tower aprox 1500m away (1 mile), 400mm F8 without TC, 400mm F11 also without TC (to isolate the diffraction effect) and 397mm F11 with TC. No upscales or downscales, only 1:1 crops.
400mm F8 without TC
400mm F11 also without TC
397mm F11 with TC
Alastair Norcross
Forum Pro
I'm not sure about that. Having just now observed how it moves when there's a breeze, I suspect that I'd need more than 1/640 to freeze it. But that wasn't what I focused on anyway, so I wasn't concerned about motion blur for that.I considered motion, but I presumed that the exposure was sufficient to freeze the object.Hi Bob, yes the vine in the 400mm shot is less out of focus than it is in the 560mm shot. That's because it moved between shots. If you look carefully at the spots on the twig behind it, you'll see that it is closer to the dark knot, which was the plane of focus, in the 400mm shot. It's also possible that it is moving in this shot, and motion blur is a factor. I don't know whether 1/640 would have been fast enough to freeze that. Also, and I don't know whether this is big enough to be visible here, the DOF for 400mm at F8 is slightly larger than for 560mm at F11 (according to online calculators). Given that the shots were equalized in size, I don't know whether that difference would show up, so the slight difference in position probably explains all the difference we're seeing here.Thanks for your efforts.
I'm a little confused, though. I look at a smaller crop of each.
The shot without the TC is at the left.
I think I see more detail in the vine, left of center.
Do you agree?
Yes. That vine is constantly swaying back and forth on a breezy day. It only takes a slight breeze to move it. I've just been out in my back yard to look at it again, and it moves whenever there's a slight gust. It's about three and a half inches in front of the knot when it's calm, but moves at least an inch in each direction when it's windy.
It only takes a split second for a gust of wind to move the vine.
Yes, that's why I questioned whether the difference in depth of field would show up when equalizing the size.
Given that the focus was on the knot in each shot, and the vine is not in the same plane of focus, any difference in how the vine looks has to be explained by it either being in a different position or moving while the shot was taken (or both). The point of the test was to see how a subject that I focused on compared between two methods of achieving the same output size of the same framing. What I focused on was the knot, so the vine is really irrelevant. It's a curiosity, but I'm pretty sure that I've solved whatever puzzle there may have been. I did the test for my own satisfaction. My experience shooting with the 100-400 with and without extender has told me that I get better results with the extender when I'm focal length limited, but I hadn't done a test like this, where I compared something as close to the same output as I could. The test has confirmed my view. I'm going to leave it at that. It doesn't matter to me at all whether other people share my view. The OP asked a question. I answered it. Some other people also answered it, some with a different answer. I performed a test to back up my answer. I think I've devoted more than enough of my time to answering the OP's question. People can looks at results, or do their own tests, and make up their own minds what works best for them. I would only encourage people always to double-check recommendations that are based on theory alone. I have been an academic for most of my life, and I have seen abundant evidence of the pitfalls of relying on theory, without checking whether that theory actually aligns with the stubborn realities of the world once put into practice.
--
“When I die, I want to go peacefully in my sleep like my grandfather. Not screaming in terror, like the passengers in his car.” Jack Handey
Alastair
anorcross
Keen hobbyist since teaching myself film photography as a teenager in the 70s, using manual SLRs and black and white film. Love photographing people and animals.
anorcross.smugmug.com
Thanks again. You've done more than I would have asked.I'm not sure about that. Having just now observed how it moves when there's a breeze, I suspect that I'd need more than 1/640 to freeze it. But that wasn't what I focused on anyway, so I wasn't concerned about motion blur for that.I considered motion, but I presumed that the exposure was sufficient to freeze the object.Hi Bob, yes the vine in the 400mm shot is less out of focus than it is in the 560mm shot. That's because it moved between shots. If you look carefully at the spots on the twig behind it, you'll see that it is closer to the dark knot, which was the plane of focus, in the 400mm shot. It's also possible that it is moving in this shot, and motion blur is a factor. I don't know whether 1/640 would have been fast enough to freeze that. Also, and I don't know whether this is big enough to be visible here, the DOF for 400mm at F8 is slightly larger than for 560mm at F11 (according to online calculators). Given that the shots were equalized in size, I don't know whether that difference would show up, so the slight difference in position probably explains all the difference we're seeing here.Thanks for your efforts.
I'm a little confused, though. I look at a smaller crop of each.
The shot without the TC is at the left.
I think I see more detail in the vine, left of center.
Do you agree?
Yes. That vine is constantly swaying back and forth on a breezy day. It only takes a slight breeze to move it. I've just been out in my back yard to look at it again, and it moves whenever there's a slight gust. It's about three and a half inches in front of the knot when it's calm, but moves at least an inch in each direction when it's windy.
It only takes a split second for a gust of wind to move the vine.
Yes, that's why I questioned whether the difference in depth of field would show up when equalizing the size.
Given that the focus was on the knot in each shot, and the vine is not in the same plane of focus, any difference in how the vine looks has to be explained by it either being in a different position or moving while the shot was taken (or both). The point of the test was to see how a subject that I focused on compared between two methods of achieving the same output size of the same framing. What I focused on was the knot, so the vine is really irrelevant. It's a curiosity, but I'm pretty sure that I've solved whatever puzzle there may have been. I did the test for my own satisfaction. My experience shooting with the 100-400 with and without extender has told me that I get better results with the extender when I'm focal length limited, but I hadn't done a test like this, where I compared something as close to the same output as I could. The test has confirmed my view. I'm going to leave it at that. It doesn't matter to me at all whether other people share my view. The OP asked a question. I answered it. Some other people also answered it, some with a different answer. I performed a test to back up my answer. I think I've devoted more than enough of my time to answering the OP's question. People can looks at results, or do their own tests, and make up their own minds what works best for them. I would only encourage people always to double-check recommendations that are based on theory alone. I have been an academic for most of my life, and I have seen abundant evidence of the pitfalls of relying on theory, without checking whether that theory actually aligns with the stubborn realities of the world once put into practice.
I have the intent to try some testing on my own. It won't include a TC, though, as I own none (yet). It may be indoors, due to winter in the NE US.
I believe there's a fundamental issue with theory (or even measurements) based on MTF. Maybe it's my limited comprehension, but I think that MTF may not be easy to relate to the "sharpness" of imaging of small features. Most of us aren't interested in imaging periodic objects.
Steve Balcombe
Forum Pro
There are so many ways to compare TC vs the bare lens:
1) Add the TC, maintain the aperture, so that the f-number increases by one stop. (This is as when shooting wide open from a fixed location.)
2) Add the TC, adjust the aperture to maintain the f-number and therefore the exposure. (This is what the camera will normally do when stopped down enough to allow it.)
3) As (1) but compare the TC image with a cropped image. (This is "R5 with TC vs R7 without".)
4) As (2) but compare the TC image with a cropped image.
5) As (1) but adjust the shooting distance to maintain the subject size in the frame. (Usual for formal IQ tests; emulates using a TC as an alternative to approaching the subject.)
6) As (2) but adjust the shooting distance to maintain the subject size in the frame.
Since any capable DoF calculator will allow you to specify the sensor size, aperture and shooting distance, you can simulate all the above, and they are all valid real-world comparisons.
To answer your specific question - the definition would normally be blur at the image plane, which should be a fixed % of the image diagonal. By default, DoFMaster uses 0.03 mm for 35 mm full frame and 0.019 mm for 1.6x crop or 0.02 for 1.5x crop. This can also be specified by the user but the interface is rather primitive. A very useful technical article by Zeiss https://lenspire.zeiss.com/photo/app/uploads/2022/02/technical-article-depth-of-field-and-bokeh.pdf acknowledges the same default circle of confusion.
Last edited:
Are blur circle criteria of 30 microns (full frame), 20 microns (1.5X crop), or 19 microns (1.6X crop) fine enough for critical work? (Not a rhetorical question.)
I haven't read the Zeiss PDF yet.
Last edited:
The advantage of using MTF is that it produces numerical results less subject to interpretation. The main problem with interpretation is confirmation bias.
The MTF Mapper software uses black quadrilaterals on a white background, and measures sharpness along the edges. So it's not periodic like line pairs per se, but the results can be converted to equivalent lp/mm, which I used for the post above.
I could have also used dimensionless cycles per pixel. With the 3.2um pixel pitch of the R7, that would be 0.13 cy/px for 39 lp/mm at 540mm f/14 with TC, and 0.18 cy/px for 55 lp/mm at 400mm f/10 without TC. The theoretical Nyquist limit is 0.5 cy/px, so we are well below that, i.e. diffraction limited.
MTF does directly relate to the ability to resolve small features in an image. It may be difficult to relate to that, but subjective reality does not trump objective reality (at least not in the real world).
The other thing with the image examples posted here is that we don't know where, when, and how sharpening has been applied to the processed images. It can be applied in the de-Bayering, and at any other stage in the process, especially JPG conversion. The MTF Mapper test I did used raw files with minimal processing prior to MTF measurement to make the measurements relevant to the real resolution captured, not pseudo resolution added later.
Steve Balcombe
Forum Pro
No, and I wish DoFMaster had a way to handle this other than entering a specific CoC.
One solution which is pragmatic rather than rigorous is to specify an aperture which is a stop larger than the one you actually wish to use. Or 2/3 stop, or whatever your experience tells you will be right for you.
Perhaps other calculators are better in this respect, but I've never researched any others.
I read it some years ago and haven't re-read it recently, perhaps I should. It labels itself 'technical' but I remember it was actually very accessible.
--
https://www.flickr.com/photos/stevebalcombe/ or
http://www.flickriver.com/photos/stevebalcombe/popular-interesting/
Last edited:
Similar threads
Keyboard shortcuts
- f
- Forum