Z 600 mm f/4 TC when not to use the tc switch

[Ken Miracle]

I think you were missing my point I am very aware of what the causes of atmospheric distortion are and yes it can happen at all focal lengths it is "less" noticeable with shorter focal lengths and yes from what I've seen 600mm in my shooting conditions show less distortion then shooting at 840mm.
I am not a wildlife photographer I mostly shoot winter sports so I am Always out in cold.temps.yet when the air temp is warmer then the snow temp or visa versa this can cause problems for me

It is going to be interesting to see how being able to go to 840 with the flip of a switch amplifies any distortion just as it does the subject. I will probably be going the other way more often from 840 with a little bird in the bush to a suddenly appearing raptor at closer range.

I was a volunteer at our local ski area for 20 years. I did some photography late in my time skiing after I had retired. If the air and snow were both cold I never noticed any distortion but never used long lenses 600mm or more for that . The most common time to see distortion on the mountain for me was spring with warm sunny temps over the colder snow. Overall with all that white and bright you do have a challenging genre.

Now my most challenging situations are usually photographing water fowl or shore bids (here in Idaho) over water. When the differential is strong between water and (warmer or colder) atmospheric distortion is a challenge even at close range when the birds are on or just above the surface an things improve as they get higher above it.

 

[Kuau]

The most common time to see distortion on the mountain for me was spring with warm sunny temps over the colder snow. Overall with all that white and bright you do have a challenging genre.

yes you nailed it warmer days and the snow is colder this is when I have the issue and for me it is amplified at 840mm

 

[Ken Miracle]

Hi Ken, at my end, I don't have to deal with cold or shooting out of the vehicle, or taking a lens out of a warm environment into a cold, it's rather the heat distortion which impacts my image quality. Recently, I went to Lakak/India (high altitude) home to a bone dry environment, high UV (11 and beyond) i.e. a fairly aggressive sun. Hence, from 8:30 / 9 am onwards till 4 pm ... the heat above the ground was just too much and though the viewfinder I could see the air glimmering and my focus struggling.

You are seeing atmospheric distortion. As I noted and @Steve does in his videos and books it does not matter if the air is cold or hot what causes the distortion is the differential in temperature between the surface you are shooting over and the air column. The air column can of course have it's own content that can alter the impact of the mixing of the temperatures between the surface and the air column. Also keep in mind that the surface ground, water, marsh, snow etc. changes temperature slower than the air. Also some surfaces create their own heat, marshes with decaying vegetation, thermal areas like Yellowstone etc.. If you have not checked out Steves videos linked in #19 above they are great.

 

[Ken Miracle]

yes you nailed it warmer days and the snow is colder this is when I have the issue and for me it is amplified at 840mm

When I am using my Z800 the scene is already amplified so I already know what I am going to get. I used to get some pretty radical distortion on those days with my maximium focal length being 300, the f/mount 28-300mm was my workhorse in those days.

 

[Ken Miracle]

yes you nailed it warmer days and the snow is colder this is when I have the issue and for me it is amplified at 840mm

You got me thinking one thing I never tried was a circular polarizer in that situation. They deal well with glare on surfaces and there would be probably some of that but not sure how it would interact with the atmospheric issues. I used them in the past when I wanted to shoot through the water surface glare, minimize it on wet foliage etc.. but there is a loss of light but on real bright days it would not matter. I have not purchased the drop in cpl for the Z800 or the Z 600 f/4 TC so no experience with using one in the conditions you are encountering on the mountain or I am encountering over water.

 

[Gov]

I thought atmospheric distortion equally affected any lens, and the main determinate was the distance to the subject. When I re-watched Steve's last video on the subject, however, he states that long lenses exacerbate the problem by "optically compressing" the heat waves, causing severely soft images. He doesn't say a longer lens has more softness than a shorter lens, but that seems to the the implication. Other posters above have said the same. So using a 600 TC with the same subject, same distance, and same atmospheric conditions, if you take one image at 840, and take another at 600 but crop it so the subject is the same size in the frame as the 840, the 840 image will be softer than the cropped 600? Or does cropping the 600 image magnify the distortion, so that both images have the same level of softness?

 

[Ken Miracle]

I thought atmospheric distortion equally affected any lens, and the main determinate was the distance to the subject. When I re-watched Steve's last video on the subject, however, he states that long lenses exacerbate the problem by "optically compressing" the heat waves, causing severely soft images. He doesn't say a longer lens has more softness than a shorter lens, but that seems to the the implication. Other posters above have said the same. So using a 600 TC with the same subject, same distance, and same atmospheric conditions, if you take one image at 840, and take another at 600 but crop it so the subject is the same size in the frame as the 840, the 840 image will be softer than the cropped 600? Or does cropping the 600 image magnify the distortion, so that both images have the same level of softness?

Part of the compression is essentially depth of field if the subject is not at infinity for the focal length of the lens. 800mm and 840 mm focal lengths have a very narrow depth of field as you get closer to the minimum focusing distance. There is more that is a "more" in focus behind than in front, essentially the old 1/3 in front 2/3 in back rule employed by landscape photographers. Of course aperture can also have an impact on depth of field. How much the image has been impacted by the distorted air in front of the target is fairly variable from very little to a lot depending what is in the air the amount of atmospheric distortion, wind, light angle, height/position in the vertical air column etc.. No one air column is the same and it can vary from moment to moment, I have noticed the most variation from shot to shot on windy days.

As I noted earlier so far when I have been using that length in those conditions it was the Z800 f/6.3 that is the focal distance I was starting at so no way of know what a 600 would have done in the same situation.