Comparing lenses for full frame vs. APS-C sensors

[pschlute]

Possibly what I'm confused about is what it means to be called a full frame lens or conversely an APS-C lens. In the case of Canon it is my understanding that the EF-S series lenses do not work on a full frame camera.

As Manfred pointed out a few posts above, an aps-c designed lens will generally have a smaller image circle than a FF designed lens. So if one used the aps-c lens on a FF camera there could be at best some vignetting in the corners, to at worst, completely black corners/edges to the picture. Now there are some aps-c lenses that will work 100% on a FF camera, or work with very minimal vignetting, but generally you should use a FF designed lens on a FF camera.

The other issue is the mount. Some manufacturers have used a different mount over time, so that can also be a barrier to using a lens on a camera for which it was not designed.

With regards Field of View (or Field of Capture), this is a property of the camera sensor, not the lens, for any given focal length. The lens produces a circular image. Generally a FF lens produces a larger image circle than an aps-c lens. So if you can mount a FF lens on an aps-c camera the image circle will cover the sensor and you will have exactly the same Field of View as if you had mounted an aps-c lens. It generally does not work the other way round, for reasons explained above.... vignetting or black edges.

What really matters to me is what focal length lens would I need to acquire for a full frame camera to match the range of view/perspective (? FoC) that I'm getting with my 18-55mm lens on my APS-C camera. What I've deduced so far is that the 24-105mm full frame lenses provide slightly more range (i.e., equivalent to 15-65mm) than that when used on a full frame camera.

You are correct. The 24-105 lens on a FF camera will give you the same FOV (FOC) as a 15-65 lens on an aps-c camera. (assuming a crop factor of 1.6)

[ajax]

...
Generally a FF lens produces a larger image circle than an aps-c lens. So if you can mount a FF lens on an aps-c camera the image circle will cover the sensor and you will have exactly the same Field of View as if you had mounted an aps-c lens. It generally does not work the other way round, for reasons explained above.... vignetting or black edges.

...

I think that fits with what I meant when saying, "larger Field of Capture (FoC) works on smaller sensor but NOT the converse" but using "Image Circle" instead of FoC would make it correct. To correct my prior hypothesis it might have been better to say "in theory a 75-300mm lens could be designed/constructed that produced an image circle sufficient only for an APS-C sensor". However, when considering the price/cost of my 75-300mm FF lens that makes no sense unless it could be done for a lot lower cost which may be unlikely in this case.

Thanks for sticking with me on this point. It is about time I understand some of this.

[Manfred M]

I think that fits with what I meant when saying, "larger Field of Capture (FoC) works on smaller sensor but NOT the converse" but using "Image Circle" instead of FoC would make it correct. To correct my prior hypothesis it might have been better to say "in theory a 75-300mm lens could be designed/constructed that produced an image circle sufficient only for an APS-C sensor". However, when considering the price/cost of my 75-300mm FF lens that makes no sense unless it could be done for a lot lower cost which may be unlikely in this case.

Thanks for sticking with me on this point. It is about time I understand some of this.

David - I have a long background in design, production and manufacturing. While my experience is not in camera / lens manufacturing, the same principles apply across many products.

I spent most of my career designing things (I'm an engineer) and the first thing that any designer asks is "what is the cost of the final product you want and how many do you expect to sell every year?". That helps dictate the materials (quality) and production processes (more automation = cheaper to make, but higher initial costs (tooling, etc)). A lens that is only going to sell a few hundred units a year (think of long focal length, large aperture lenses used by sports and wildlife photographers) versus a lens that will sell tens of thousands of units). A lens directed at the amateur market can be less robust because it is not expected to see the hard use of a pro lens that is going to have higher demands put on it. A lens where they user is going to post on the internet is going to need a lot less sophisticated design that a pro who is going to turn out wall-sized prints. My f/2.8 14-24mm lens cost over twice as much my f/3.5 - 5.6 28-300mm lens (and the more expensive lens is a LOT heavier).

I hope this all makes sense.

[William W]

. . . I became interested in developing photos I felt like I needed to be able to produce raw files to maximize the potential quality of resulting images. I opted for an inexpensive bundle (Canon EOS Rebel T6 also known as EOS 1300D) which included a pair of zoom lenses (18-55mm & 75-300mm). . . I do have an interest in acquiring a camera with a full frame sensor.

. . . comparable shots taken on a full frame sensor. For example, when looking at potential full frame lenses a couple of options that I'm thinking might work are either 24mm-105mm or 24mm-200mm but I feel like I need to know what the corresponding values would be for comparable shots on my APS-C sensor.

> On the lenses you would need for a "full frame" camera to mimic the Range of the FoV (Field of View) that you already have:
1. to replicate the EF-S18 to 55 you'll require something like - 24 to 70 or 24 to 105 or 28 to 70
2. to replicate the EF 75 to 300 you'll require something like - 120 to 500

> On the what you do with the lenses you have if you move to a Canon 'full frame' camera
1. you will not be able to use the EF-S18 to 55
2. you will be able to use the EF75 to 300 (i.e. gaining somewhat a large portion of the zoom range you already have)

> A general comment on the discussion (and your queries) about image quality if moving to a Canon 'full frame' camera. Notwithstanding the excellent advice/commentary concerning megapixels, etc., I think that a (if not 'the') limiting factor of general image quality will be the EF 75 to 300 lens. I assume it is the EF 75 to 300 F/4.5~5.6 MkIII, as this is the model variant which is usually sold as a bundle kit lens for APS-C Canon cameras. A consideration is that when you mount this lens on a FF camera, you will be using all of its Image Circle, unlike when using it on your APS-C camera, the sensor only sees the centre bit of the len's Image Circle - which is the bees knees good bit. I reckon you will see a difference.

> On something easily overlooked - If you move to Canon FF, do not underestimate the value of IS (Image Stabilization) in your "standard zoom lens". I expect you have it in your 18 to 55, but not in the 75 to 300.

> On my opinion - I reckon you need to assess if moving to "Full Frame" is what you need/want. There are many ways to skin a cat.

Most importantly - before spending money - ask more questions, seek more information which directly address you needs and aspirations.

WW

[xpatUSA]

Going off at a tangent regarding "APS-C", I find it interesting that the actual standard measure is 1.4 crop compared to Canon's 1.6 ...

[rpcrowe]

I think that fits with what I meant when saying, "larger Field of Capture (FoC) works on smaller sensor but NOT the converse" but using "Image Circle" instead of FoC would make it correct. To correct my prior hypothesis it might have been better to say "in theory a 75-300mm lens could be designed/constructed that produced an image circle sufficient only for an APS-C sensor". However, when considering the price/cost of my 75-300mm FF lens that makes no sense unless it could be done for a lot lower cost which may be unlikely in this case.

It is beyond theory... Sony has the 70-350mm E-Mount lens for APSC format (or full frame in crop mode only). NO, this lens is not lower in cost than most full frame 70-300mm zoom lenses. However it is significantly lighter in weight and smaller in size than a full frame lens of close to equivalent focal length.

When I shot Canon, my long-lens setup was the Canon 7D with the EOS 100-400mm IS L Mk.1 lens. I now use the Sony A6600 with the 70-350mm f/4.5-6.3 E-Mount lens. I have 50mm less reach but, I gain about 30mm at the wide side. Price? The Sony setup is less expensive but, the primary attribute of that setup on my Sony a6600 is that it is about 1/3 the weight of the Canon setup. The size is also considerably smaller.

The image quality and auto-focus of the Sony gear is equal to that of my Canon setup and the combination of OSS and IBIS equals or surpasses the IS of my Canon combination.

[xpatUSA]

Going off at a tangent regarding "APS-C", I find it interesting that the actual standard measure is 1.4 crop compared to Canon's 1.6 ...

... also interesting are the various terms or acronyms that describe how much of a scene gets captured by a sensor ...

I also puzzle over "image circle" ...

[ajax]

...

> On the what you do with the lenses you have if you move to a Canon 'full frame' camera

...

My immediate interest in FF is with the standard to wide zoom rather than telephoto. While I have just come to realize that my telephoto zoom could be used on a FF camera it looks to me like a better lens would be more appropriate, which looks to be quite consistent with your suggestions.

Also, it only took me a few weeks to recognize that switching lenses was a real nuisance. I got lucky and found a good price on another camera body that matched the one in my kit. That was well worth it from my point of view. Based on discussion herein I am leaning in the direction of sticking with APS-C in the telephoto case when/if such an upgrade comes into play. Maybe I'll give it (my current 75-300mm) a try should I get a compatible FF camera body but I'm guessing that will be just to satisfy some curiosity. In that, learn what happens when you do it.

[pschlute]

Going off at a tangent regarding "APS-C", I find it interesting that the actual standard measure is 1.4 crop compared to Canon's 1.6 ...

aps-c the film, had a 1.44 crop factor to 35mm film.

Digital sensors have varied in size from the outset both between brands and within brands.

aps-c sensor size has no standard measurement.

[pschlute]

I also puzzle over "image circle" ...

Care to elaborate.

[ajax]

I thought it worth elaborating on what is my main motive for starting this discussion. Manfred has mentioned in a couple of his replies what caused him to want higher quality images. In that, migrate from crop censor to full frame. I think my motive is the same as his.

To my way of seeing it, in this context, higher quality refers to the data captured by the camera. Obviously, there is more than that needed to produce a high quality picture. As I started to learn about how digital images can be developed using computers (i.e., post processing) I quickly wanted raw files from the camera and I have mine set to produce only raw files. While NOT nearly as expensive as full frame, my crop frame kit was fairly expensive when compared to a couple of point and shoot cameras I’d used previously and for the money and simplicity the quality of those images is quite remarkable but they do not provide raw files. However, when it comes to data quality there are 2 basic properties provided by raw files that are important. The first is precision. Even the sensors used in those cheap point and shoot cameras (possibly also phones which I know nothing about) are capable of detecting more than 8 bits of precision. However, the jpeg (jpg) format used for the files they produce only supports 8 bits of precision. The second has to do with what I’d say is why the files are called raw. The data that represents what each pixel detected is recorded in the file and has NOT been changed by anything the camera does. That data cannot be viewed. What you see on your camera’s screen after taking a picture is the camera's attempt to develop it and at least in the cameras that I’ve used it ends up in the jpeg format. Very similar process to what point and shoot cameras produce. While these files are relatively small, jpeg is called a lossy compression format for a reason. What gets lost is more that just precision the compression algorithm also discards information/data. In that, when you decompress the file, to view the picture, you loose information/data that was present when the file was compressed.

I suspect that there is no new news there for most, if any, of you. I only include it as a reminder of what capabilities the cameras we’re discussing provide. As someone who spends a great deal of time and effort developing each file which is thought worthy of turning into a picture, retaining all of that data/detail (quality) is an important part of my work flow (which by the way took a long time to develop and remains a work in process). As an aside I sort of suspect that those of you who are pros trying to earn money from your photography skills couldn’t possibly justify spending the amount of time and effort I’m spending on every picture. Possibly those pros trying to earn income from selling the pictures they’ve photographed (i.e., artwork that is probably printed) may share my thinking. However, such effort is a luxury that we amateurs can often afford if desired.

As mentioned often herein there are many situations where there is NO benefit from having all of this high precision data. However, the main point is that you can scale down or convert the raw data in post processing to whatever might fit that situation. However, if the detail provided by raw data from the camera is NOT captured there is NO way to scale up in the post processing that recovers the lost detail/quality. I generally start my work flow by developing the raw file into an uncompressed 16 bit file in tiff format which is what I’ve found to be the most universally supported format (i.e., can be viewed by lots of software) that retains all of the detail. These tend to be very large files but given today's much lower cost of high capacity disk drives I do NOT find this to be a problem for the number of files I'm dealing with. Very few of the shots I take end up being developed. If I want to share something on whatever kind of media it can be converted into what makes sense.

[pschlute]

I thought it worth elaborating on what is my main motive for starting this discussion

You may be over-thinking this.

I too convert raw to tiff....but then I produce 8 bit jpeg for posting online.

When I print I convert my tiff file to 8 bit jpeg for the commercial printing company to use to produce my print.

For an amateur (like me) the majority of online images or prints will probably look the same whether the image is captured on FF or aps-c.

My advice is to continue learning about PP and FF , but do not expect it will produce anything much different from using a jpeg straight out of an aps-c camera

[xpatUSA]

aps-c the film, had a 1.44 crop factor to 35mm film.

Yes, 1.435153244 according to my calculator.

Digital sensors have varied in size from the outset both between brands and within brands.
aps-c sensor size has no standard measurement.

Yes, as is well-known to most of us. It begs the question at what point does a sensor become not-APS-C?

[pschlute]

Yes, as is well-known to most of us. It begs the question at what point does a sensor become not-APS-C?

I think this character had the answer to that when he said "When I use a word, it means just what I choose it to mean"

[xpatUSA]

Care to elaborate.

A circle is a round thing with an exact diameter or several exact diameters in the case of thick circles, say roundels.

An "image circle" has no exact diameter because the said image has no exact peripheral dimension. Like an old soldier, it simply fades away as one goes from the center outwards. Perhaps there is some lens manufacturer's standard that defines the exact loss of light which defines the said periphery and thereby the image circle's "diameter". If there is, I am unaware of it ... you?

[xpatUSA]

I think this character had the answer to that when he said "When I use a word, it means just what I choose it to mean"

LOL - and thank you for "Sensor Size 101" - I have now learned how to suck eggs ...

[Manfred M]

Manfred has mentioned in a couple of his replies what caused him to want higher quality images. In that, migrate from crop censor to full frame. I think my motive is the same as his.

Higher quality images for large format printing, David, not for viewing on the computer / posting on the internet. Smaller sized sensors are more than adequate unless you plan to make large prints.

As an aside, if I were getting into a new camera system today, I would likely not go full-format, but would go directly to either a FujiFilm GFX100S or the Hasselblad 907X, medium format cameras. Both are at an appropriate price point versus full format and with the medium format sensor, I would get an even larger image to work with. As the Fuji is a true 100MP, 16-bit camera that is likely the direction I would go versus the Hasselblad. I understand that Hasselblad uses rebranded FujiFilm lenses.

[xpatUSA]

... The second has to do with what I’d say is why the files are called raw. The data that represents what each pixel detected is recorded in the file and has NOT been changed by anything the camera does.

Not true, sorry. Many cameras apply pre-processing e.g. tone curves to what the sensor outputs before writing to the so-called "raw" data file - usually at a greater bit depth than the camera ADC (analog to digital converter).

That data cannot be viewed.

Not true. Programs such as RawDigger can send "raw composite" data from the file to a screen unchanged by conversion to RGB e.g. demosaicing.

What you see on your camera’s screen after taking a picture is the camera's attempt to develop it and at least in the cameras that I’ve used it ends up in the jpeg format.

Please pardon my pedantry.

[DanK]

Higher quality images for large format printing, David, not for viewing on the computer / posting on the internet. Smaller sized sensors are more than adequate unless you plan to make large prints.

As an aside, if I were getting into a new camera system today, I would likely not go full-format, but would go directly to either a FujiFilm GFX100S or the Hasselblad 907X, medium format cameras. Both are at an appropriate price point versus full format and with the medium format sensor, I would get an even larger image to work with. As the Fuji is a true 100MP, 16-bit camera that is likely the direction I would go versus the Hasselblad. I understand that Hasselblad uses rebranded FujiFilm lenses.

This thread has meandered quite a bit, and while there is nothing wrong with that, I think it's important to keep the OP in mind, and this would in my opinion be very bad advice for David. David is wondering whether the next step up for him from a beginner's kit should be full frame. I and others have suggested that it might or might not be, depending on what he is going to shoot. However, I'm willing to walk the plank and say that jumping to medium format would be a big mistake for him. It makes sense for some people, e.g., people who shoot landscapes and print very large, but it would be a bad choice for David, from what he has written. It would be a bad choice for me as well, given what I shoot and how much I lug my gear around.

I'm guessing that you didn't intend it as advice for him, but it would be hard for him to know.

David--If you go to my website and look at the "built environment" gallery, you will see photos taken with a cheap Lumix micro four thirds camera, a 50D (an old crop camera with an older sensor than yours), a 5D Mark III (I think 22 MP), and a 5D Mark IV (30 MP). I'm guessing that if you don't click on the little information links, you won't be able to tell which images were taken with which camera. You can see differences once you print at about 13 x 19, but I have a 13 x 19 of one of the Lumix images that is both in my wall and in a gallery. Once you get past 13 x 19, especially if you crop, one can sometimes see a small difference between the crop and FF, but it's usually not big. Keep in mind that all but one of these cameras is old, with sensors that aren't up to current standards.

So I'll walk a little further out the plank. Unless you are printing very large or shooting a lot in low light, I think the choice between FF and crop won't make a large difference for you. What will make a difference if you shoot wildlife or macro is pixel density, and for that, crop sensors are usually superior. All that aside, the biggest factor apart from the photographer influencing how sharp images look is usually lenses. A few years ago, I would have suggested that the first step might be replacing the 75-300, which is the weakest link in your kit. However, it's a different world now because DSLRs are disappearing, and it may not make sense to buy another lens designed for them if you are going to end up with a mirrorless body. YOu can add an adapter to use them with mirrorless bodies, but it might work out best to have a plan for what system you want to end up with.

Dan

[William W]

. . .This thread has meandered quite a bit, and while there is nothing wrong with that, I think it's important to keep the OP in mind, [...]

Unless you are printing very large or shooting a lot in low light, I think the choice between FF and crop won't make a large difference for you. What will make a difference if you shoot wildlife or macro is pixel density, and for that, crop sensors are usually superior. All that aside, the biggest factor apart from the photographer influencing how sharp images look is usually lenses.

Concur.

Wherever you move (or not): Main priority apropos general IQ is: Lenses, Lenses, Lenses.

WW