vertical shots with 70-300 and sharpness

[waardij]

Hello. I am not new to this forum in that I have been looking in for a long time. I learned a lot.
Below is a experience I would like to share and find out if others have experienced the same
I recently bought a RRS L-bracket for my a900. When using it with the sony 70-300 zoom I found vertical shots at 200 and 300mm to be seriously unsharp (1/30e shutter).
At first I thought there to be something wrong with the L-bracket (it is not extremely stiff in the vertical position). More experiments, on a heavy tripod with the legs short, showed that also when I used the camera in 90 degrees rotated head, the results where far from sharp. In a horizontal position the sharpness is excellent. I used mirror lock up for all tests.
When thinking about it, I realized that the shutter curtain moves vertical. This movement accelerates and stops directly in the direction of the center of the tripod. All vibration is in the vertical plain, in which the tripod is very stiff. In the vertical position the shutter movement tries to twist the camera sideways, in which direction both the L-bracket and the tripod offer less resistance.
I tried this theory by putting the camera on a nodal slide of RRS, in a horizontal position, as far as possible behind the center of the tripod. And yes, the results where not as poor as in the vertical position, but no longer critical sharp.
Could it be that this is a weakness of the a900? I never experienced this problem with the D2x I used before (that is less critical with its 12Mp, but still).

sorry if the post is a bit long.

Hans van Driest

 

[peterv]

Hello and welcome,
do you switch off Steadyshot while on a tripod?

 

[Dave_Anderson]

Welcome, Hans. Interesting, I have not noticed an issue but could try some experiments, also with lenses that have tripod collars to remove the L-plate from the equation. What is below the L-plate, BH, tripod, etc?

 

[waardij]

Steady shot was turned off. Although I also tried it with SS on. When using a pano head in windy conditions steady shot often helps a lot to counteract the wind induced movements. It did not help in this case.

Hans

 

[waardij]

At first I used my normal tripod, a Gitzo GT2531EX and the standard GH2750QR head. On top of the head I use a RRS PLC1 for connecting the camera.
Since this is a rather light tripod, I also tried it on a heavy Gitzo reporter, with a PLC 1 directly attached to the tripod, no head in between.
On both tripods the behavior was comparable, although the vertical shots where slightly better on the reporter. I did most of the testing indoor, so there was no wind to influence the results.

 

[Braeside]

Like Dave I have not noticed this, but rarely use a tripod on the A900. I don't have an L bracket, as my longer lenses have collars.

It sounds like the body/lens combo is resonating and may need damping, can you try hanging a bean bag over the lens and see if that helps to damp it?

 

[waardij]

Well, I have not tried a bean bag, but most everything else. For example I tried a support under the lens. I even tried a second tripod on the (now vertical) horizontal part of the L-bracket. This second tripod under an angle to the ground. The second tripod did help, but the results still was not critically sharp. Only when I supported the second tripod to a wall (the tripod horizontal), did I obtain the same image quality as I get with the camera in a horizontal position.
I think that from now on I will only use the camera horizontal with this lens (on a tripod) and stitch two images when I need the vertical resolution. When sharp, this lens is really nice. And I know the 80-400 is even sharper, but that one is so heavy.

 

[Braeside]

Yes Hans, I have to 70-400 now, I sold the 70-300 when I got the A900 to replace the A700. I don't find that I use the new lens as much because it is big and heavy and so I do not always carry it with me, unlike the much smaller 70-300.

It is a very nice lens though and I am well enough pleased with the results.

 

[Braeside]

Hans,

Just tested my A900 with 70-400 on Manfrotto 190PROB with 488RC2 ball head.
Indoors at close distance - speeds 1/30 to 1/5 at 400mm and found no difference in sharpness between vertical and horizontal with tripod collar.

(Turned off Steadshot as that completely ruined things on the tripod as expected).

I will try rotating ball head instead and test again.

 

[Braeside]

Hans, Hung the A900 with 70-400 on tripod collar off the side of the ball head and rotated between vertical and horizontal, again no difference in sharpness at 400mm 1/8 sec.
(all tests with SS off and 2 second timer)

 

[dhsimmonds]

I use the 70-300G on both the A900 and A700 bodies. It is sometimes slow to focus, particularly on the A700 body. With the new firmware though it is much quicker on the A900.

I have just returned from a 2 week holiday in Central America where for airline weight restrictions I took the 70-300 in preference to either my 70-400 and Tamron 200-500 (my favourite lens for wildlife). All used handheld by the way!

I managed to get some nice wildlife shots with both bodies, but oh boy did I miss the bigger lenses! I wish I had not taken my Macbook Pro and taken the 70-400 in lieu of the 70-400.....lesson learned!

I spent 2 weeks in Botswana last September and managed more "keepers" with the 70-400 with the same two bodies, again all handheld letting SSS and high shutter speeds or ISO do the work!

Nope, the 70-300 is definitely not my favourite lens!

 

[Braeside]

Hi Dave, sounds like a great trip. These aircraft restrictions are getting to be a huge problem. Carry on weight limits like 5Kg make it very hard to take much gear.
Need big pockets and a partner willing to share some weight.

 

[waardij]

David, thank you very much for trying this out.
Maybe the problem is specific then for the body on a tripod with a long lens. Having a collar on the lens apparently solves it. The weight of the 70-400 probably also helps to dampen the shutter vibration.
Once again, thanks!

Hans van Driest

 

[Braeside]

Hans, You are welcome, I am just sorry that I do not have a 70-300 to test for you here now.

I wonder if it would be possible to get some kind of tripod collar made for the 70-300?

Maybe someone else has a 70-300 here and could test on a tripod for you, just to make sure it is not something wrong with your A900 body. (I could only imagine a fault with the SS system not holding the sensor steady in one axis that would cause that problem).

 

[Dave_Anderson]

I only have three lenses in the same weight class as the 70-300 that do not have tripod collars, the 16-35(+50g), the 135(+150g), and the Minolta 28-135(-100g). The 135 seems like the best one to try this evening since the UWA probably won't show vibration as much and the other zoom isn't as sharp as the prime to begin with.

 

[waardij]

I have been thinking about a problem with my camera, the sensor moving in one direction. I did check the operation of SS and it seems to work fine. And would a movement of the sensor be sensitive for the focal length of the lens? The sensor is behind the lens and I would expect movement there to be a problem at all focal lengths.

Hans van Driest

 

[peterv]

The way I understand it, the SS behavior differs with various focal lengths.

 

[Dave_Anderson]

As Peter says, it is FL-dependent. The camera factors in the detected movement vs FL in use to decide how much to move the sensor. I think it may factor in shutter speed as well, I'll check that too.

 

[Dave_Anderson]

OK, I didn't get to it last night but I carved out the time tonight. I tried to reproduce the OP's results using the following parameters:

• a900, 135Z, ISO 800, aperture priority, MLU, center focus point, lens racked to infinity prior to each shot.
• Aperture: starting at f/11, then each full stop down to wide open(skipping f/2)
• Shutter: ranged from 1/5 to 1/250, respectively
• 3 shots at each setting, letting the camera settle for a 2-count after raising mirror, then repeat all in vertical position
• Subject: Part of an information card on a piece of exercise equipment @ 20 feet, 6 point type
• Light was 3 mini par lamps, track lighting about 12 feet from subject(adjusted to maximize light on subject)
• Sturdy Tiltall tripod with RRS lever-QR

I figured the ISO was as high as I could go and still get meaningful results, I needed this to get a typical range of shutter speeds (I wanted a few stops above and below the 1/30 mentioned in the OP).

For the most part, I found the results didn't really show any degradation in the vertical position. Most of the vertical shots were just as sharp as the horizontal shots. The exceptions appeared to be missed focus in a couple of cases but also it seems that I may not have let the camera settle enough toward the end. When I started, EXIF shows I was taking at least 15-20 seconds between shots. I started with horizontal orientation. Toward the end I sped up quite a bit, 10, 8, even 6 seconds between shots -- so I might not have been allowing enough time for settling. The pictures showing the most blur are at speeds of 1/80 and higher, as I neared the end. I guess I'm not the most patient tester late at night.

All of the pics shot at f/5.6 or higher(1/5 to 1/25) were equally sharp horizontal or vertical. Wider open, faster shutter speeds, it was a mixed bag with more blur in the vertical shots where I was moving faster. But some (more than 1/2) of the vertical shots near wide open were just as sharp as the horizontal shots.

Some vertical shots were sharper than horizontal shots taken with the same settings.

To the OP: I'd suggest you make sure the L-plate is secure on the camera. You can go pretty tight without risk of damage. Also, the tripod that you mentioned has a lot of parts to it, even with the column all the way down I can't see it being as stable as a conventional tripod. Try mounting the camera and lens, and tapping on the lens(both horizontally and vertically) while you look through the viewfinder. It should settle down almost instantly, with little or no visible oscillations. If it fails this test maybe it's just not up to supporting that heavy of a camera/lens combo.

 

[waardij]

Dave, thanks very much for the effort you put in.
I must say however that it is not a coincidence I mentioned 200 en 300mm as the problem lengths. With the 70-300mm at 135mm I do not have problems either. It is strange, it almost seems as if the relation between blur and focal length is not linear. Going from 135mm to 300mm is slightly more than a factor of two, so I would expect the blur to double. In practice I do not see a problem at 135mm (or only very slight) and sometimes several pixels at 300mm.
As far as the tripod go, I share your concern That’s why I also tried it on the Gitzo reporter, which is not light at al. On that tripod I did not use a ball head but just a clamp, directly screwed to the tripod. And did helped, but it did not solve the problem.
Furthermore I made a bracket with two RRS components from my pano head. This gave a much stiffer ‘L-bracket’ then the regular one. Also on the reporter it still gave some blur in the vertical position.
When using the camera on the reporter and tapping it, the damping is very good. On the lighter tripod it is certainly less. The nice thing is that the horizontal shots are also really good on the lighter tripod.
Like I mentioned earlier, I think I will accept the behavior as a fact, and will stitch two or more shots when I need the vertical resolution. I like to print large (at least 16x24) and are very critical concerning resolution (something the a900 certainly can give).

Hans van Driest