XF 100-400 soft image at long distance or user error?

[sunkengoose]

I got a XF 100-400 mm used a while back and used it successfully to take pictures of birds at "medium" distances like on trees when I'm on a trail. The pictures are sharp for the most part.

Today, I had the opportunity to photograph a snow owl at long distances with my X-T50. Maybe 100-200m away or more. The 400mm is not enough and some very soft images were produced. I'm not sure if this is my fault somehow? For reference, this is what I did:

1. Handheld as I forgot my tripod
2. 1/2000s produced the best shot (used 1/500s earlier), but I didn't think it was needed because the owl was not moving for the most part. Even the vegetation around looks soft. I used F5.6 and tried F8. F8 was sharper but not by much. The weird softness is still there, but it had a wider DoF.
3. Used manual focus because AF didn't work that well, and the owl is not moving.
4. Temperature was cold, but the air was still

Here's the best result. There are photos that are worse. I feel like this is significantly worse than what I did before, but this is a new distance record for me for birds for sure.


X-T50 best result.

Here's a worse one:


X-T50 not so good results

I also had a Sony HX99 with me. I used it to take some photos at its 720mm equivalent and used a 2x digital zoom. It almost feels sharper with more noise. Here's the result


HX99 with 2x zoom

One interesting note is that the bird later flew away to a post even further, and I feel like I got better result than the earlier photos shown? What am I doing wrong here? Is my lens bad?


X-T50 owl on post that's even further.

 

[a_c_skinner]

I realise all that I'm just intrigued about the suggestion of a phenomenon I've only seen in UK on hot clear days. It is then most noticable over tarmac but I guess your explanation makes sense. What I'm wondering about is if it reaches the magnitude to interfere with photos to the extent seen.

 

[Truman Prevatt]

I realise all that I'm just intrigued about the suggestion of a phenomenon I've only seen in UK on hot clear days. It is then most noticable over tarmac but I guess your explanation makes sense. What I'm wondering about is if it reaches the magnitude to interfere with photos to the extent seen.

Bill's explanation is right on the money as to the cause. The refractive index of air varies with temperature. So even minor temperature gradients at ground level will cause a continuous and almost random vibration of refractive index along a long path from subject to the camera. . That will have the effect of a scattering of light through the air. The further the subject reflecting or emitting light is away the more the scattering this effect. Added to that, a long focal length lens magnifies this scattering on the sensor.

The fact that this image is taken with the subject sitting on the ground maximizes this effect as it is sitting at the source of the radiation.

The case you refer is an extreme case. On a hot day driving down a road paved with black top, the road in a distance can appear wet because the refractive index near the air road boundary "bends" the light to the point of some appearing to the reflected off the road as would be the case if the light were reflected off of wet pavement. The same phenomenon causes the mirages in the desert that appear as water in a distance. There are other examples.

Where does the "water" come from in a mirage?

First, I would like to clarify that I know why a mirage is formed, what I want to know is why is it that when a mirage is formed it appears that a pool of water is present. Like for a palm tree in a

physics.stackexchange.com

 

[a_c_skinner]

Every day is a school day as they say. I've seen the pool of water mirage of course, though not recently which I suspect is changes in UK roads - the surface is now covered in traffic.

I remain cautious about the magnitude of the effect on days such as illustrated.

 

[Erik Baumgartner]

Besides the subject being too far away to occupy a suitable area of pixel density, it looks to me that the primary issues are the blown highlight detail on the front of the bird and maybe slightly missed focus (stuff around the bird looks sharper). If the highlights are intact in the RAW file, I'm betting you could coax some significant additional detail out of the bird with some fine-tuning of your processing. If the highlights are truly toast (maybe, maybe not), consider using the highlight warning blinkies and some exposure compensation as needed next time.




The highlights can't be properly recovered from the jpeg, but it looks noticeably sharper with just a little quick tweaking in Lightroom. 100% view. If you want to make your highlight detail look soft, overexposing/overISOing it (and/or not processing it optimally), is a very good way of going about it. If you’re shooting RAW there’s no good reason to be shooting at ISO 1000 here when you could have had a full extra stop of highlight headroom at ISO 500 (-1 EV of exposure compensation) with no significant downsides.

 

[Bill Ferris]

I realise all that I'm just intrigued about the suggestion of a phenomenon I've only seen in UK on hot clear days. It is then most noticable over tarmac but I guess your explanation makes sense. What I'm wondering about is if it reaches the magnitude to interfere with photos to the extent seen.

The last photo shared by the OP is of the bird perched atop a pole. It's above the ground level heat transfer and air turbulence and, while the bird is still much too distant to show good detail, it's not as impacted by atmospheric unsteadiness.

The main issue in the photos is the subject being too distant and too small in the frame. If the OP had been able to be within 20 meters or so of the bird, the photos would have shown more detail even if perched on the ground.

 

[a_c_skinner]

"ubject being too distant and too small in the frame"

Without doubt!

 

[sunkengoose]

Genuine question from me:

Is atmospheric conditions likely at obviously low temperatures? Ground and air likely similar temperatures. I'm wondering about the physics of this.

The ground absorbs solar energy during the day and radiates heat energy at night. If exposed to a clear night sky, the sky acts as a black body. In short, heat transfer doesn't stop when the ground and air above the ground reach the same temp. The ground continues radiating heat as long as there's a clear night sky above.

Black body radiation is why a vehicle parked outside in an unsheltered location overnight in winter will have frost on the windshield while a vehicle parked a few feet away in the same temperatures but sheltered beneath an overhang will not.

In wintry conditions, the daytime air temperature can be anywhere from 10+ degrees warmer to 10+ degrees colder than the temperature of the ground. That sets up situations where heat transfer at ground level will destabilize the air immediately above the ground.

Combine this with a subject that's teeny tiny in the frame and you've got a recipe for photographs that lack sharpness & detail.

If the OP finds that photos of subjects filling most of the frame are sharp & detailed, that would tend to confirm the conditions (air turbulence at ground level combined with a subject that's small in the frame) produced the unsatisfying results.

Thank you for this explanation. It didn't occur to me but it does make a lot of sense. It is the same effect people get when photographing across a long stretch of asphalt road, you get distortion due to heat. It also perfectly explains why the owl is sharper on the pole without the "ghost-like effects" of the photos on the ground. I suspect the Sony picture looks like it doesn't have this "ghost-like effect" because it is too low detail to begin with and the body likely applies a lot of sharpening.

If the OP had been able to be within 20 meters or so of the bird, the photos would have shown more detail even if perched on the ground.

I would have loved to be closer to the bird! Someone actually did attempted to approach the owl with a big tripod. This resulted in the bird being scared and thus flew away to the pole .

For reference, I was also able to get perfectly sharp photos of other birds closer to me with this lens, which is why I was so surprised. Here's a reference:

 

[jhorse]

This is a great explanation and probably a more likely cause of the softness in the circumstances than my contribution. In the UK it is not much of an issue as a norm!

 

[kmhwildlife]

Capa's rule applies, although not for the same reasons he gave the advice he is attributed for giving.




"If your photos aren't good enough, you aren't close enough."




The closer you are, the less interference there will be from atmospheric haze. Why? Less atmosphere for the light to reflect off your subject and travel through to your lens and camera. Super telephoto lenses do offer longer working distances but you still want to be much closer to your subject than many people recognize.

 

[kmhwildlife]

And there lies one of the conflicts between birders and photographers over owls.






Many birders, especially ones without experience using super telephoto lenses, think that a big lens should be able to makes these kinds of distance shots without approaching closer to the subject. It simply isn't the case and they've not looked at the physics to understand why not.





Many photographers who have experience with super telephoto lenses recognize they need to be closer and are looking to make a better image than just an ID pic or checklist snapshot.





There are ways of approaching animals that spook less often than not but it is always a risk and in my experience should not be taken once an animal has gained an audience of more than one party. I prefer to look at the situation and imagine where I might go next were I the subject. In that way I can be in position and ready for the subject to approach closer to me instead of myself to them.

 

[fecl]

very nice shot