Cropped sensors better for landscape work. Huh?

[NorthernFocus]

Recently I've been contemplating a new landscape lens for Nikon DX format which is what I typically carry when traveling (smaller/lower weight). But my DX body is the 24MP D7100 which begins to show effects of diffraction at f8 or so. Not exactly the best candidate for landscape work, right? By looking through DX landscape shots I've made over the years, the majority of them have been at 24mm or higher (36mm FF equivalent). So out of curiosity I broke out the trusy DOF calculator to see how useful the D7100/24mm combo is at f8. I was pleasantly surprised with the numbers. Here is a full frame vs 1.5 crop comparison shooting at f8 and focused at 12 ft.

DX format, 24mm, DOF = 6ft to infinity
FX format, 35mm, DOF = 7ft to 41ft

Shocking

Of course this is only half the story. The full frame sensor isn't diffraction limited as quickly. Pinch it to f11 and the DOF results are virtually identical to the cropped sensor at f8. And of course diffraction isn't the only thing to be considered. But it's just another example of doing the math rather than reading someone's blog that's telling you that you must use full frame cameras for "serious" landscape work.

[dje]

Hi Dan

Let me preface my remarks by saying that this whole business of lens performance and sensor resolution is one I'm still trying to get a proper handle on - so I'm happy to be shown the light !

I assume when you say "The full frame sensor isn't diffraction limited as quickly" you are referring to pixel pitch and resolving ability ?

I would have thought that you should be considering diffraction limiting in relation to the lens rather than the camera sensor. As I understand it, for large apertures, the effects of lens distortion are far more significant than diffraction, in relation to sharpness. As you reduce the aperture, the lens distortions start to have less effect on sharpness and the effects of diffraction increase. At some point, particularly for a good quality lens, diffraction may become a significant contributor to loss of sharpness.

However when it comes to assessing the affect of sensor pixel pitch on the image produced by the lens on the sensor surface, then the lens characteristic as a whole is what matters, ie the characteristic of the lens that is the combined result of distortion and diffraction, not just diffraction by itself.

It would be nice if lens manufacturers published MTF information that showed how MTF drops off with line spacing (as distinct from how MTF varies with distance out from the centre). The line pairs per mm at which MTF drops to 50 is often quoted as a useful figure. This to me gives a better indication of how well a lens performs in the sharpness stakes as the traditional curves only show MTF figures for line spacings of 10 pmm and 30 pmm which typically for any decent lens are quite high (in the centre at least).

Dave

[chauncey]

I am a fan of LULA and to that end, I would submit this...http://www.luminous-landscape.com/es...s_part_2.shtml
Or, more on point...http://www.luminous-landscape.com/es...t-Lenses.shtml

[Glenn NK]

Dan, I think that diffraction is a lens issue, not a sensor issue (AFAIK). Many lenses start to show diffraction effects at around f/8 (and lens tests such as those done by Photozone clearly show this), but many photographers are using f/11 and f/16 without any significant effect.

Your numbers showing the DOF for FX vs DX are puzzling. When doing DOF calcs using the online calculator with different formats, I think the focal length of the lens used in the calculator should be the same for both DX and FX because the focal length doesn't change with the sensor size. When I used the f/stops and focal lengths in your example, I got the same results you did, but when I left the focal length the same, the DOF values were very comparable.

Glenn

[DanK]

Glenn,

Dan's right: diffraction limits are affected by pixel pitch, and therefore, diffraction kicks in at a larger aperture (smaller f-stop number) with crops. See the "Lens diffraction" tutorial on this site. However, my experience jibes with Colin's: it often doesn't make much difference. Printing at 8 x 10 (roughly A4), I've gone to f/20 with the a crop sensor without degradation that anyone else but me noticed.

Re DOF: I didn't do the calculations, but I see why Dan did what he did. He is comparing the DX with a 24mm to an FX with the focal length that would provide the same field of view. I think that is the most informative comparison.

Like the other Dan, I have both formats, and I think for most purposes, the differences are minor. I prefer the FF for low light and if I expect to print large, but the fact is that when I grab my 5DIII, it is often for entirely unrelated differences between it and my old 50D--e.g., far better AF, better ergonomics, more logical and intuitive controls. In many cases, I really doubt others will see the difference in the final product.

[dje]

Glenn,

Dan's right: diffraction limits are affected by pixel pitch, and therefore, diffraction kicks in at a larger aperture (smaller f-stop number) with crops. See the "Lens diffraction" tutorial on this site.

DanK

This tutorial considers how diffraction blur relates to pixel pitch. However surely the same approach could be taken in regard to any sort of blur caused by the lens. Hence my contention that it is the overall lens performance that counts (which includes the relative effects of lens distortion and diffraction at any particular aperture).

Dave

[TonyW]

Hi Dan,

I am relatively inexperienced in photography but I think I understand the maths pretty well. All of what you say seems right to me and the message is that to get a certain depth of field with a FF camera you should use a smaller aperture than with a CF. As you point out, the diffraction limit (if that is important) is higher with a FF because generally the pixel pitch is larger (assuming you are comparing cameras of around the same age). Also, generally speaking, with a FF you can use a higher ISO so that if you use a larger f number you can still get the same shutter speed.

You are talking about a focus distance of 12ft, which is pretty small for what people normally think of as being a landscape. If you use even 20ft as the focus distance, the difference in the depth of field between FF and CF is much less.

It does not seem that there is a case for saying that CF cameras are better for landscapes but I am sure that people with CF cameras can get good landscape pictures.

[Brev00]

Diffraction limited does not mean a wall of ugliness pops over your image if you shoot at f 11 or smaller. Do not fear diffraction! If you are just viewing you image on your computer at some enhanced magnification, the effects of diffraction can be seen. But, what does your f 11 image look like at normal viewing levels? Printed? I just think deciding one's photographic approach from a concept is limiting to one's creativity. You are in control, not some rule.

If, however, this is not persuasive, then I suggest you buy a landscape lens that has wider focal lengths. The dof you get at 14mm and f 8 will be quite sufficient.

[DanK]

If, however, this is not persuasive, then I suggest you buy a landscape lens that has wider focal lengths. The dof you get at 14mm and f 8 will be quite sufficient.

Not entirely. Again, look at the tutorials on this site. This is from the tutorial on DOF:

Note that focal length has not been listed as influencing depth of field, contrary to popular belief. Even though telephoto lenses appear to create a much shallower depth of field, this is mainly because they are often used to magnify the subject when one is unable to get closer. If the subject occupies the same fraction of the image (constant magnification) for both a telephoto and a wide angle lens, the total depth of field is virtually* constant with focal length! This would of course require you to either get much closer with a wide angle lens or much further with a telephoto lens,

The reason people think of wide angle lenses as having greater DOF is that they are usually used so that the subject occupies less of the frame.

[Glenn NK]

Glenn,

Dan's right: diffraction limits are affected by pixel pitch, and therefore, diffraction kicks in at a larger aperture (smaller f-stop number) with crops. See the "Lens diffraction" tutorial on this site. However, my experience jibes with Colin's: it often doesn't make much difference. Printing at 8 x 10 (roughly A4), I've gone to f/20 with the a crop sensor without degradation that anyone else but me noticed.

Re DOF: I didn't do the calculations, but I see why Dan did what he did. He is comparing the DX with a 24mm to an FX with the focal length that would provide the same field of view. I think that is the most informative comparison.

Like the other Dan, I have both formats, and I think for most purposes, the differences are minor. I prefer the FF for low light and if I expect to print large, but the fact is that when I grab my 5DIII, it is often for entirely unrelated differences between it and my old 50D--e.g., far better AF, better ergonomics, more logical and intuitive controls. In many cases, I really doubt others will see the difference in the final product.

OK, but is the difference in diffraction between FF and APS-C significant?

In regard to changing the focal length, I still think this is faulty because the lens does not change between the two bodies. What happens with a crop sensor is that the outer area is in effect masked off because the sensor is smaller - the focal length does not change.

I tried using a 24 mm lens on both the Nikon DX and FX bodies, and the difference in DOF was definitely not significant.

http://www.dofmaster.com/dofjs.html

And I would think that dofmaster allows for the pixel pitch difference - and the difference in DOF is pretty darn small.

However, look what happens with a lens:
http://www.photozone.de/canon_eos_ff...35tse2?start=2

I have this lens, and if the landscape is flat (ocean landscape), I shoot at f/3.5 or f/5.6, and use the tilt to change the plane of focus. I've never used it at f/16.


Glenn

[NorthernFocus]

...He is comparing the DX with a 24mm to an FX with the focal length that would provide the same field of view. I think that is the most informative comparison....

So did I but as I frequently do I did not appreciate how differently we all view the world.

The intent of the thread was simply to point out that there are many means to a given end. I do most of my photography with long lenses so haven't spent that much time studying the geometry associated with wide angle stuff. Many things pointed out here are accurate. DOF calculations are a mathematical attempt to predict subjective perception, and diffraction effects are gradual, and lens abarations at wider apertures may be much more relevant than diffraction, and etc.

But I am firmly in the camp as described in the LULA article that was linked. Essentially, details do count. Individually some details may be insignificant. But collectively? Isn't it simple logic to eliminate as many variables as one can realizing that there are always going to be things that are sub-optimal under field conditions?

The takeaway from the exercise for me is that for landscape photography I will start shooting wider apertures and paying more attention to my focal point to optimize the performance of my gear. To date it has just been easy to set f22 and fire away. Just another possible step along the path of continuous improvement

[rpcrowe]

Take a look at Roman Johnson's great landscape images, many of which were shot with a crop sensor Nikon.
http://www.pbase.com/romansphotos

I shoot with crop gear because 1. I love the 7D cameras, 2. I love the 17-55mm lens and 3. Landscapes are just part of my work.

If I were shooting landscapes primarily or only, I would probably opt for a 24-70mm f/2.8L ii and a 70-200mm f/4L IS on 5Dii or 5Diii cameras...

[Colin Southern]

So did I but as I frequently do I did not appreciate how differently we all view the world.

The intent of the thread was simply to point out that there are many means to a given end. I do most of my photography with long lenses so haven't spent that much time studying the geometry associated with wide angle stuff. Many things pointed out here are accurate. DOF calculations are a mathematical attempt to predict subjective perception, and diffraction effects are gradual, and lens abarations at wider apertures may be much more relevant than diffraction, and etc.

But I am firmly in the camp as described in the LULA article that was linked. Essentially, details do count. Individually some details may be insignificant. But collectively? Isn't it simple logic to eliminate as many variables as one can realizing that there are always going to be things that are sub-optimal under field conditions?

The takeaway from the exercise for me is that for landscape photography I will start shooting wider apertures and paying more attention to my focal point to optimize the performance of my gear. To date it has just been easy to set f22 and fire away. Just another possible step along the path of continuous improvement

Personally, diffraction doesn't enter the equation when I'm shooting; it's just too "small" to worry about IMO. Usually though - for landscape - exposure duration is the "problem child" and as a result I'm usually shooting at whatever optimises that (often F22 / F32).

I find that one can try to optimise as many variables as one wants, but after a while the excessive/compulsive traits start to take over and nothing gets shot; at the end of the day some things matter and some things don't; experience is what separates the two ("real world" as I like to put it). Striving for perfection is great (I always do) but knowing when to stop over-thinking and just "take the damn shot" is more important, for me anyway -- and diffraction definitely comes into that category.

[NorthernFocus]

OK, but is the difference in diffraction between FF and APS-C significant?...

Significant is a subjective term in this case. And it's not FF vs APS-C that matters but pixel pitch. Nikon D7000 and D800 have essentially the same pixel pitch. And it's not only diffraction that matters but resolving capability of the lens as a whole. Whether it makes any practical difference (i.e. whether it is significant) depends on how/what one shoots and for what purpose.

In regard to changing the focal length, I still think this is faulty because the lens does not change between the two bodies...

The geometry changes assuming you're trying to cover the camera sensor with the same image with the two different formats. Think about it from that perspective. If you are limited to standing in a particular spot, what would you have to do to capture the same image with the two formats in question and how would they perform.

...And I would think that dofmaster allows for the pixel pitch difference - and the difference in DOF is pretty darn small...

Pixel pitch doesn't factor into the DOF calculation. Sensor size (aka crop factor) is the what makes the difference.

...However, look what happens with a lens:
http://www.photozone.de/canon_eos_ff...35tse2?start=2

I have this lens, and if the landscape is flat (ocean landscape), I shoot at f/3.5 or f/5.6, and use the tilt to change the plane of focus. I've never used it at f/16.

Part of the challenge in these discussions is realizing that we each have a different frame of reference. For example I shoot a lot of landscapes with no horizon in them and/or I'm trying to include significant elements in the composition that are within 10 feet of the lens. What is and isn't significant to each of us depends on context.

[Manfred M]

Have a look at some MFT charts for various lenses. I think you will find that while hitting the diffraction limit does have a real impact, it is really minor; rather in the same order of shooting with a lens wide open or stopped down one stop.

I will continue to shoot wide open, just like I will use apertures of f/16 and higher, as the shooting situation requies.

[Brev00]

Not entirely. Again, look at the tutorials on this site. This is from the tutorial on DOF:

The reason people think of wide angle lenses as having greater DOF is that they are usually used so that the subject occupies less of the frame.

My understanding of dof involves using the dof calculator to determine the, drumroll, dof. In that calculation, focal length is a key variable. 14mm at f 8 on a D7100 has an almost unlimited dof while the dof at 24mm and f 8 is much more confined.

[Glenn NK]

By looking through DX landscape shots I've made over the years, the majority of them have been at 24mm or higher (36mm FF equivalent). So out of curiosity I broke out the trusy DOF calculator to see how useful the D7100/24mm combo is at f8. I was pleasantly surprised with the numbers. Here is a full frame vs 1.5 crop comparison shooting at f8 and focused at 12 ft.

DX format, 24mm, DOF = 6ft to infinity
FX format, 35mm, DOF = 7ft to 41ft

There was something that bothered me, but apparently I missed it in previous posts:

Maybe one should not focus the two bodies (DX and FX) at the same distance to maximize DOF?

Focusing the FX body with a 35 mm lens at 17.9 feet provides 8.93 ft to infinity which isn't quite as good as the DX/crop body, but it's much better than 7 ft to 41 ft.

The 24 mm lens on the DX body would be maximized by focusing at about 12 feet.

In addition to focal length and f/stop, there is another key variable - focus distance.

Just a thought.

Glenn

[DanK]

My understanding of dof involves using the dof calculator to determine the, drumroll, dof. In that calculation, focal length is a key variable. 14mm at f 8 on a D7100 has an almost unlimited dof while the dof at 24mm and f 8 is much more confined.

Of course it is, but that is only part of the issue, as the tutorial explains. Suppose that you put the 24mm on your camera and frame an image as you want it. You then decide to switch to a 14mm. If you stand in the same place, you will now have more DOF. However, you will no longer have the framing you want--the image that would have filled the frame no longer does. So, you march forward until the framing is what you wanted. At that point, DOF will be similar to what it was with the 24mm, although other aspects of the image won't be.

One thing that will differ is that you will have less background blur with the shorter focal length, but background blur is not the same as DOF. The difference in background blur for a constant DOF is a function of the angle of view of the lens. For an excellent discussion of the difference between background blur and DOF, including some good images illustrating the issue, see http://toothwalker.org/optics/dof.html.

[steve welle]

Back to the original post, being new to this site I was quite surprised to read that someone was concerned about going with smaller aperture than f/8 because of diffraction. I have done landscapes with both cropped and full sensors and never saw diffraction as a significant factor even at f/22 with normal viewing conditions. Of course when looking for it with close scrutiny there is some diffraction but with 10 x 15 inch or even larger prints this has essentially no impact on how "good" the image is. Lighting, composition, subject matter are so much more important than extreme sharpness of far distant objects in my opinion. The nice thing about landscapes is they don't move so you can retake shots with various aperture settings if worried about getting the perfect balance between dof and diffraction blur. I agree with conclusion of OP that one should not believe anyone who says you have to have full frame for serious landscape shots. But I do like the fact that I get wider angle with full frame without having to buy a shorter lens.

[NorthernFocus]

...Maybe one should not focus the two bodies (DX and FX) at the same distance to maximize DOF?

Focusing the FX body with a 35 mm lens at 17.9 feet provides 8.93 ft to infinity which isn't quite as good as the DX/crop body, but it's much better than 7 ft to 41 ft....

And would be wonderful unless there is something 8 ft away that you want included in the frame and want to be in focus all the way to the horizon

Another benefit of APS-C not yet mentioned is the fact that only the center portion of the image is captured where the lens is sharpest and has the least distortion. Another one of those little things, each of which add to better overall IQ...