Testing a Sony A7sii for macro

Images of undisturbed subjects in their natural environment. All subject types.

Moderators: rjlittlefield, ChrisR, Chris S., Pau

Scarodactyl
Posts: 1617
Joined: Sat Apr 14, 2018 10:26 am

Re: Testing a Sony A7sii for macro

Post by Scarodactyl »

There's nothing wrong with it, but I think it's maybe a bit more roundabout than it needs to be, depending on the background of the reader? If I understand right there's still no inherent effect from the sensor size, just from one method of getting around the crop factor to capture the same FoV by using a different focal length (vs a speedbooster or teleconverter). I think this probably makes more intuitive sense if you're approaching it from a traditional photography point of view where using totally different lenses for different sensor size cameras to get equivalent FoVs is kind of assumed , but it might be a bit confusing if you're coming from a more microscopy-focused point of view since resizing the image to fit a sensor size is ubiquitous, as is not and having a strong crop factor, neither of which has any effect on DoF. That's kind of a guess though, since I'm almost clueless on normal photography tech, everything I know is from learning about microscopy and macro, and I think that is why it initially confused me.

rjlittlefield
Site Admin
Posts: 23562
Joined: Tue Aug 01, 2006 8:34 am
Location: Richland, Washington State, USA
Contact:

Re: Testing a Sony A7sii for macro

Post by rjlittlefield »

Scarodactyl wrote:
Sun May 23, 2021 6:57 pm
There's nothing wrong with it, but I think it's maybe a bit more roundabout than it needs to be, depending on the background of the reader?
I assume that you're referring to "Sensor size: how does it matter?".

I know very well that the reception of those words depends heavily on background of the reader. What I don't know is how to make it better, for people who have trouble with it in its current form. The Wikipedia article expresses the same concepts, but IMHO it's not exactly a paragon of clarity either. Here's their treatment, not including diffraction and noise:

WikipediaSnippet.jpg

I would be delighted to have somebody write some version of the same material that is both technically correct and more easily digested. It would make a good reference.

--Rik

Dalantech
Posts: 694
Joined: Sun Aug 03, 2008 6:57 am

Re: Testing a Sony A7sii for macro

Post by Dalantech »

rjlittlefield wrote:
Sun May 23, 2021 7:45 pm
I know very well that the reception of those words depends heavily on background of the reader. What I don't know is how to make it better, for people who have trouble with it in its current form. The Wikipedia article expresses the same concepts, but IMHO it's not exactly a paragon of clarity either. Here's their treatment, not including diffraction and noise:


WikipediaSnippet.jpg


I would be delighted to have somebody write some version of the same material that is both technically correct and more easily digested. It would make a good reference.

--Rik
But that article is really inaccurate. The only way to make the field of view the same between sensors is to either crop the full frame image so that the field of view is the same, use a different lens focal length, or change the magnification. Cropping the full frame image yields the best comparison, but that's rarely considered.

That piece also mentions "Using the same absolute aperture diameter for both formats with the "same picture" criterion (equal angle of view, magnified to same final size) yields the same depth of field." At the same magnification and Fstop all sensors will produce the same depth of field. Any deviation is due to changes in test parameters to keep the field of view the same between different sensors by changing the magnification instead of simply cropping the full frame image. Since depth of field in macro is a function of the Fstop and aperture (lens focal length is irrelevant) then changing the magnification is going to change the depth of field.

The only other aspect to consider is the circle of confusion, but pixel densities are so high now that the difference in the CoC between sensors creates negligible differences in depth. There simply is no magic in a crop factor sensor, and it's called a "crop factor" and not a "multiply every aspect of photography factor" because it's just a crop -functionally no different than cropping a full frame image in post.

If you really want to watch the world burn hop onto a M4/3 forum and tell them that they're not shooting at 2x when they use a standard macro lens...

rjlittlefield
Site Admin
Posts: 23562
Joined: Tue Aug 01, 2006 8:34 am
Location: Richland, Washington State, USA
Contact:

Re: Testing a Sony A7sii for macro

Post by rjlittlefield »

John, I wonder if you read my posting on what turned out to be the page before this one.

I suspect not, so let me repeat it here for everyone's convenience.
rjlittlefield wrote:
Sun May 23, 2021 4:23 pm
Dalantech wrote:
Sun May 23, 2021 1:06 pm
There are numerous people claiming that smaller than full frame sensors provide more depth of field, ignoring the simple fact that it's easier to fill the frame at lower magnifications with them and it's that lower mag the accounts for the increase in depth.
Please read my words here very carefully. Do not skip ahead because you think I'm disagreeing with you. I'm not.

First, it is absolutely critical to keep in mind what is being held constant.

Smaller sensors give more depth of field IF you shoot the same size subject at the same F-number.

But in that case they also give more noise and more diffraction blur in the final image.

The resulting image from small sensor is exactly the same as from a larger sensor stopped down farther, varying effective F-number in direct proportion to the sensor size.

That is, f/8 on Micro Four-Thirds will give more DOF but also more noise and diffraction blur than f/8 on full frame, and exactly the same as f/16 on full frame.

In other words, there is no real advantage to smaller sensors regarding DOF. But if people don't keep straight what's being held constant, it can look like there is.

The main source of conflict that I see comes from people not being clear about what's being held constant.

Earlier, I linked to a thread about equivalent images analysis. The thread is titled "Sensor size: how does it matter?" It was written 13 years ago, and no errors have been found in it since then.

You might find it helpful to thoroughly study and absorb what I've written there.

As far as I can tell, the point that you're trying to make is exactly what the analysis in the thread shows.

Adding some thoughts......

Much earlier, you wrote:
Shoot with a full frame camera like Canon's 5Ds (51MP) and crop it down to a 1.6x field of view (roughly 18MP) and the pixel density will be exactly the same. Mask off that full frame senor with tape to a 1.6x crop and the images will look just like the cropped in post full frame shots.
I agree completely with that statement. It totally shows that the 18 MP crop sensor cannot do any better than the cropped-in-post 51 MP sensor.

But making the comparison in that way is weak, because it relies on throwing away 33 megapixels of information that cost money to acquire.

A stronger statement is to observe that with the fullframe sensor you can get the same framing, same DOF, same diffraction blur, same overall noise, and retain the full 51 megapixels, by scaling the optics and the camera settings in proportion to the sensor size.

In other words, the smaller sensor never wins the DOF battle, unless the contest is rigged.

I would have thought that you'd be delighted by that conclusion, but instead you keep objecting. Why?

--Rik

Dalantech
Posts: 694
Joined: Sun Aug 03, 2008 6:57 am

Re: Testing a Sony A7sii for macro

Post by Dalantech »

rjlittlefield wrote:
Mon May 24, 2021 10:08 pm
John, I wonder if you read my posting on what turned out to be the page before this one.

I suspect not, so let me repeat it here for everyone's convenience.
rjlittlefield wrote:
Sun May 23, 2021 4:23 pm
Dalantech wrote:
Sun May 23, 2021 1:06 pm
There are numerous people claiming that smaller than full frame sensors provide more depth of field, ignoring the simple fact that it's easier to fill the frame at lower magnifications with them and it's that lower mag the accounts for the increase in depth.
Please read my words here very carefully. Do not skip ahead because you think I'm disagreeing with you. I'm not.

First, it is absolutely critical to keep in mind what is being held constant.

Smaller sensors give more depth of field IF you shoot the same size subject at the same F-number.

But in that case they also give more noise and more diffraction blur in the final image.

The resulting image from small sensor is exactly the same as from a larger sensor stopped down farther, varying effective F-number in direct proportion to the sensor size.

That is, f/8 on Micro Four-Thirds will give more DOF but also more noise and diffraction blur than f/8 on full frame, and exactly the same as f/16 on full frame.

In other words, there is no real advantage to smaller sensors regarding DOF. But if people don't keep straight what's being held constant, it can look like there is.

The main source of conflict that I see comes from people not being clear about what's being held constant.

Earlier, I linked to a thread about equivalent images analysis. The thread is titled "Sensor size: how does it matter?" It was written 13 years ago, and no errors have been found in it since then.

You might find it helpful to thoroughly study and absorb what I've written there.

As far as I can tell, the point that you're trying to make is exactly what the analysis in the thread shows.

Adding some thoughts......

Much earlier, you wrote:
Shoot with a full frame camera like Canon's 5Ds (51MP) and crop it down to a 1.6x field of view (roughly 18MP) and the pixel density will be exactly the same. Mask off that full frame senor with tape to a 1.6x crop and the images will look just like the cropped in post full frame shots.
I agree completely with that statement. It totally shows that the 18 MP crop sensor cannot do any better than the cropped-in-post 51 MP sensor.

But making the comparison in that way is weak, because it relies on throwing away 33 megapixels of information that cost money to acquire.

A stronger statement is to observe that with the fullframe sensor you can get the same framing, same DOF, same diffraction blur, same overall noise, and retain the full 51 megapixels, by scaling the optics and the camera settings in proportion to the sensor size.

In other words, the smaller sensor never wins the DOF battle, unless the contest is rigged.

I would have thought that you'd be delighted by that conclusion, but instead you keep objecting. Why?

--Rik
Sorry Rik, didn't mean to come across like I was disagreeing with you. But some of the material you referenced, like that Wikipedia article, was a rigged test because the field of view was being held constant without cropping the full frame image in post. It's only in the post quoted above where you said that "the smaller sensor never wins the DOF battle, unless the contest is rigged." Very well said!

I don't think my 5Ds masking comparison is weak at all -it eliminates the possibility that someone is gonna argue about pixel density or a difference in the circle of confusion when comparing completely different sensors. It drives home the fact that a crop is a crop no matter how it's done. Of course I wouldn't mask off that sensor, but simply crop images in post to get the subject size that I want.

As for noise and diffraction you and I have completely different standards since my goal is to create an image that looks good edge to edge (I'm not too concerned about per pixel sharpness), and to photograph critters that don't sit still (not possible to focus stack). Diffraction takes my lunch money but at the relatively low mags that I shoot at I'm just losing a little texture detail. By using a very well diffused light source close to the subject (to keep the flash duration as short as possible), taking control of what motion I can prevent, and using a sharp lens I can keep that detail loss due to diffraction to a minimum. So for me shooting with a crop factor sensor works since I can take advantage of that built in crop to shoot at lower magnifications and still get the framing that I want verses shooting full frame. I could just as easily shoot with a 5Ds and crop in post, and it's tempting.

rjlittlefield
Site Admin
Posts: 23562
Joined: Tue Aug 01, 2006 8:34 am
Location: Richland, Washington State, USA
Contact:

Re: Testing a Sony A7sii for macro

Post by rjlittlefield »

John, I'm still struggling to figure out how you think about the world.

So please, humor me here...

I understand your scheme for reproducing the crop sensor's picture using fullframe, by using the same lens and cropping in post.

But now, suppose I want to reproduce the fullframe sensor's picture, using the crop sensor. What do you tell me?

--Rik

Scarodactyl
Posts: 1617
Joined: Sat Apr 14, 2018 10:26 am

Re: Testing a Sony A7sii for macro

Post by Scarodactyl »

I had a more careful read through it, and I think where it becomes confusing to me is the initial assumption that the field of view remains the same between images. That kind of bends my intuition, since field of view is the only thing that changes with differing sensors unless you also change the optics. The field of view changing is so intuitively connected to the physical sizes of the image circle and the sensor that it kind of explains itself. From there it feels maybe easier to explain that if you then use a different lens to adjust the field of view the lens will perform differently in other ways too (or, if you used a teleconverter/speedbooster or shorter/longer tube lens or different projection eyepiece or whatever with the same lens to change the field of view, it would behave pretty much just the same). From there the advantages or disadvantages of a given format are mostly just a matter of lens/camera logistics rather than optics.
The FoV assumption leads to statements like this one: "The resulting image from small sensor is exactly the same as from a larger sensor stopped down farther, varying effective F-number in direct proportion to the sensor size", which is totally correct on a technical level, but is also maybe easy to misread as saying there is an actual connection between sensor size and how effectively stopped down a lens is. You go out of your way to clarify that there is not just a little further on in the post, but I wonder if the framing is what invites the confusion in the first place. But again, maybe that's not confusing at all if the reader has a serious background in normal photography--almost everything I know about cameras and photography I've learned from studying photomicrography, so my perspective is definitely skewed.

rjlittlefield
Site Admin
Posts: 23562
Joined: Tue Aug 01, 2006 8:34 am
Location: Richland, Washington State, USA
Contact:

Re: Testing a Sony A7sii for macro

Post by rjlittlefield »

Scarodactyl wrote:
Tue May 25, 2021 10:23 pm
initial assumption that the field of view remains the same between images
If you have trouble thinking of same FOV as being an assumption, then try thinking of it as being a goal. That opens the question of how to achieve it.

Hence the question I posed to Dalantech: "suppose I want to reproduce the fullframe sensor's picture, using the crop sensor. What do you tell me?"

--Rik

Dalantech
Posts: 694
Joined: Sun Aug 03, 2008 6:57 am

Re: Testing a Sony A7sii for macro

Post by Dalantech »

rjlittlefield wrote:
Tue May 25, 2021 8:29 pm
John, I'm still struggling to figure out how you think about the world.

So please, humor me here...

I understand your scheme for reproducing the crop sensor's picture using fullframe, by using the same lens and cropping in post.

But now, suppose I want to reproduce the fullframe sensor's picture, using the crop sensor. What do you tell me?

--Rik
I too am struggling to understand why you and I can't have a conversation that doesn't turn hostile, or result in you putting me down and belittling me...

What do you mean by "I want to reproduce the fullframe sensor's picture, using the crop sensor."? Do you mean pixel density (resolution), dynamic range, etc? I'm not even remotely concerned with producing images that make the most of my sensor or my lens, because those kind of "technically competent" images are rarely the photos that people save to their PC desktop or phone as wallpaper. They're also not the images that get the attention of image editors that are looking for photos to print. No one, outside of this niche community, cares about MTF charts, shooting at the peak resolution of a lens or sensor, per pixel image sharpness, etc. The vast majority of the people who follow my work are looking for images that look good edge to edge. It's only after they take an interest in one of my photos that they start asking me "How many images did you take for that focus stack?" or "What focusing rail do you use?" or "How much do you crop in post?" I was getting those questions so frequently that I started adding "This is a single, uncropped, frame taken hand held." to the tech specs that I post with my images. Some people have gotten bent by it, cause they take it like I'm bragging. But I just got tired of answering the same questions over the over. Still get asked when people don't take the time to read. Was even asked "How can you shoot at that magnification and camera settings hand held with natural light?".

So why would I need to "reproduce the fullframe sensor's picture"? Other than maybe an increase in dynamic range what would I possibly gain? Even when I print my images poster size I get the same standard questions by the people who view them.

Last, but most certainly not least, if my light quality was garbage what difference would shooting full frame make? I see people taking triple digit focus stacks that lose more detail to blown highlights and micro contrast than I ever lose to diffraction. But most of my discussions with other macro shooters de-evolve into just getting enough light to expose a scene, and all they care about is avoiding diffraction.

So much more to conciser when trying to create a photo that people outside of this community will appreciate than the simple, and lets be honest, easy technical details. Anyone can create a technically competent photo that makes the most out of the gear that they use. Not too may who can take a photo of an insect that changes the attitude of the viewer in a positive way, or that shows personality or attitude.

Probably more of an answer than what you were looking for, or maybe even the wrong answer to your question. But maybe you've got a better understanding of what drives me. I'm just not one of those people who can't see the photo cause the pixels are in the way. Not saying you are, but the macro discipline is most certainly dominated by them...

Dalantech
Posts: 694
Joined: Sun Aug 03, 2008 6:57 am

Re: Testing a Sony A7sii for macro

Post by Dalantech »

rjlittlefield wrote:
Tue May 25, 2021 11:38 pm
Scarodactyl wrote:
Tue May 25, 2021 10:23 pm
initial assumption that the field of view remains the same between images
If you have trouble thinking of same FOV as being an assumption, then try thinking of it as being a goal. That opens the question of how to achieve it.

Hence the question I posed to Dalantech: "suppose I want to reproduce the fullframe sensor's picture, using the crop sensor. What do you tell me?"

--Rik
Just saw that reply. So you're only question is "What if I want to maintain the same field of view as a full frame sensor"? Uh, shooting at a lower mag with the crop factor sensor would do it. You'd also get a nice bump in depth of field provided the aperture and magnification doesn't change. Pretty much the reason why I shoot with a crop factor camera. But changing the magnification (or lens focal length) and then claiming that you can get more depth just by changing sensors isn't logical. The sensor isn't the reason for the change. It's pretty easy, and unscientific, to draw a straight line between two completely unrelated points to "prove" that something is true. That's the reason why some "enlightened individuals" (aka idiots) looked at the Covid infection maps and the 5G coverage maps and claimed that 5G causes Covid...
Last edited by Dalantech on Wed May 26, 2021 3:30 am, edited 1 time in total.

Dalantech
Posts: 694
Joined: Sun Aug 03, 2008 6:57 am

Re: Testing a Sony A7sii for macro

Post by Dalantech »

Depth of Field Myths: Does Focal Length & Sensor Size Affect DoF? <-- That video explains the sensor comparison problem better than I can, although I've run into a few people who will pull some of what Gerald says out of context cause they just don't wanna admit that they were wrong. Or what they want to believe about the gear they use has almost become a religion. It's not perfect, but Gerald does a pretty good job of explaining some of the flawed logic that people use.

My .02 on everything photography related is that the technical details aren't nearly as important as what I can create with the gear and techniques that I use. If my images look like snapshots then there really isn't anything separating me from someone who's using a point and shoot camera. I may have to cop the attitude of a lot of the shooters that I admire and simply get off of forums altogether, cause getting mired down in some of these discussions isn't worth it. I can't teach macro if there is no agreed upon frame of reference, and that's the only reason why I even get involved in these posts. I've actually run into one individual who thought that her photo of a mountain range was a macro photo just cause she took it with a macro lens...

rjlittlefield
Site Admin
Posts: 23562
Joined: Tue Aug 01, 2006 8:34 am
Location: Richland, Washington State, USA
Contact:

Re: Testing a Sony A7sii for macro

Post by rjlittlefield »

Thanks for the reference. That's an excellent video. So are his two earlier videos, Crop Lenses on Crop Bodies: How It Works vs Full Frame (APS-C & M43) and Aperture & f-stop Myths Debunked: The Importance of the Entrance Pupil.

From my standpoint, these are useful references because (1) they have a very different style from what I usually link to, so they will appeal to different people, and (2) everything he says is not only correct but is also easily cross-referenced against my usual material that says the same things in different ways.

With respect to the current conversation, probably my favorite section of the DOF video is the part where he says "In order to achieve the same framing on a Micro Four-Thirds camera as you would on a fullframe camera", and then works his way along to this summary:

7.27_of_YouTube_1bzHn2cKwLI.jpg

Earlier, he makes a point about what matters for DOF (assuming same framing):

2.50_of_YouTube_1bzHn2cKwLI.jpg

This is, of course, the very same direction I was headed when I asked my question.

To capture the same image on a smaller sensor, he's using here an appropriately shorter lens with a smaller F-number, such that the entrance pupil stays in the same location and has the same diameter. These are key aspects of "equivalent images". (Elsewhere in the video he talks about using the same lens on the smaller sensor, and moving farther away. That preserves the magnification of the subject, but the foreground/background relationship changes so while the magnification stays the same, the overall image does not.)

These videos do not touch on the subjects of diffraction or noise levels, but in most cases there's no need to get down to that level of detail. It's a marvelous serendipity that if you get the same perspective, framing, DOF, and shutter time, with the same illumination, then you also get the same diffraction blur and shot noise.

The main result of all this analysis is simple: over a wide range of situations, all sizes of sensors can shoot the same images.

So, worrying about sensor size and magnification is mostly just a distraction. What matters is what the image shows.

On that point I think we can agree.

--Rik

gardenersassistant
Posts: 190
Joined: Sun May 31, 2009 5:21 am
Location: North Somerset, England

Re: Testing a Sony A7sii for macro

Post by gardenersassistant »

rjlittlefield wrote:
Tue May 25, 2021 11:38 pm
Scarodactyl wrote:
Tue May 25, 2021 10:23 pm
initial assumption that the field of view remains the same between images
If you have trouble thinking of same FOV as being an assumption, then try thinking of it as being a goal. That opens the question of how to achieve it.

Hence the question I posed to Dalantech: "suppose I want to reproduce the fullframe sensor's picture, using the crop sensor. What do you tell me?"

--Rik
Interesting discussion. It seems to depend on where you are coming from. I move freely between four sensor sizes: 1/2.3", MFT, APS-C and full frame. It is essential for me to have some rules of thumb, derived as it happens from a mixture of experimentation and calculation, that let me get images of the type I want irrespective of the kit I am using. This is a thoroughly practical issue for me. Consider for example:

This image captured with a P&S 1/2.3" sensor bridge camera
Image
1902 1 P&amp;S P1490474_PLab4 LR 1300h DNAI DNAIc by gardenersassistant, on Flickr

This image captured with a micro four thirds camera
Image
1902 2 MFT P1110730_PLab4 LR 1300h DNAI DNAIc by gardenersassistant, on Flickr

Or this image captured with a P&S 1/2.3" sensor bridge camera
Image
1902 3 P&amp;S P1740215_PLab4 LR 1300h DNAI DNAIc by gardenersassistant, on Flickr

This image captured with a micro four thirds camera
Image
1902 4 MFT P1047172_PLab4 LR 1300h DNAI DNAIc by gardenersassistant, on Flickr

This image captured with a full frame camera
Image
1902 5 FF DSC01916_PLab4 LR 1300h DNAI DNAIc by gardenersassistant, on Flickr

I need to know how effective apertures and hence DOF and diffraction blur map between these setups, what ISOs produce similar noise levels for these setups, and how flash power plays into all this. Incidentally I also need to know how close-up lenses affect effective aperture differently from other magnification arrangements, and how teleconverters affect effective apertures. For me, it is all about how to capture a particular scene with particular kit, effectively handling the interlinked issues of depth of field, diffraction blur, noise and flash power. Considering a constant field of view is for me the natural and practical way to handle these issues.
Nick

Flickr
Blog
Journey since 2007

Rework and reposts of my images posted in this forum are always welcome, especially if they come with an explanation of what you did and how you did it.

Dalantech
Posts: 694
Joined: Sun Aug 03, 2008 6:57 am

Re: Testing a Sony A7sii for macro

Post by Dalantech »

rjlittlefield wrote:
Thu May 27, 2021 9:19 pm
...The main result of all this analysis is simple: over a wide range of situations, all sizes of sensors can shoot the same images.

So, worrying about sensor size and magnification is mostly just a distraction. What matters is what the image shows.

On that point I think we can agree.

--Rik
Exactly that. In my experience the only time anyone asks me how I took a shot, or what I used to take it, is if they like how the image looks when viewed edge to edge. So it's really the photo that matters most.

Post Reply Previous topicNext topic