SAL70400G

[peterottaway]

Bossel, I'm not certain that modern high performance lenses actually require filters for photo quality reasons but I have equipped almost all my lenses with Marumi DHG Lens Protect filters ( tele ) or Hoya Pro 1 UV filters ( wides ) for peace of mind.

Local geographical conditions ranging from mediterranean to semi arid to arid with strong winds blowing up summer dust storms mean I prefer to be cautious when out in the field. Winds blowing up a combination of ultra fine grit combined with salt are not my idea of fun.

Also as with the shot of Kingfisher on the ledge photographing vultures, many photographers can lose their sense of physical awareness and take a tumble when shooting on broken ground. Better a filter than a lens.

[bossel]

Thanks Peter and David. Maybe I was just overly scared that these filters harm picture quality, but it seems it's not the case

[harvey]

I recently noticed my 49mm filters (for the 50mm f/1.7 and not-used 28mm f/2.8) were very old. I generally have Hoya filters and their newer ranges don't go down to 49mm. I was not sure if my UV filter was coated on both sides and all I could get was the UV HMC.

Maybe I should have looked at other ranges also.

I should maybe replace my 49mm Hoya PL-CIR also (it is probably 22 years old).

I noticed Hoya have new polariser film in their HD filters and are claiming better light transmission for the visible range...

http://www.hoyafilter.com/products/hoya/HD-01.html

But they are very expensive and I don't need the hardness.

Harvey

[henniebez]

I got a new filter today. They have exchanged it without any problems. They also ran some test, and it was remarkable to see the difference. The problem is not that obvious shooting subjects 5-7m, but going futher 10-20m the results are shocking!

At least I know now how to test focus, back focus and I have met the head technician of Sony South Africa. I guess it was all worth it.

Thanks for the help.

[Jonathan K]

Hi there,

since the problems of the OP seem to be more or less solved, I hope you don't mind me "hijacking" the thread for a question concerning my own 70-400G, which I got yesterday:

When testing the lens in the shop, I noticed that the lens would not focus with the shop owners A350, my own A700 made it focus very, very slowly, especially when going from minimum distance to infintiy. The other way around is always faster.

I didn't buy that specific lens, we agreed it was faulty and he sent it back, he got me a new one in two days time:
It seems better, but the basic problem is still visible:

At longer focal lenghts (300-400mm) it has a lot more trouble to focus, especially when moving from minimum distance (1,5 m to infinity), it can take up to 3-4 seconds...
Of course the problem is more severe in suboptimal lighting conditions, but it is also noticeable in daylight.

Could somebody explain to me what happens when you zoom to 300-400mm? I always use the central AF-sensor (never learned to use the others) and I tried it with ans without the Tamron UV filter. Or is it just the fact that I expect too much or that the enormous magnification at 400mm gets the AF-sensor to read less contrast? I remember my Sigma 400/5.6 which was hunting like mad...

Anyway your help is greatly appreciated.

PS: I made the lens focus with the lens cap on. It focuses at the same speed in both directions which makes me rule out a faulty HSM motor.

Thanks in advance,

Jonathan

[bossel]

PS: I made the lens focus with the lens cap on. It focuses at the same speed in both directions which makes me rule out a faulty HSM motor.

Wouldn't this rather indicate a faulty motor?

Anyway, I only had a few minutes to play with an 70-400 on my A700 earlier this year and I didn't notice what you describe. I rather thought it focuses quickly.

[Jonathan K]

PS: I made the lens focus with the lens cap on. It focuses at the same speed in both directions which makes me rule out a faulty HSM motor.

Wouldn't this rather indicate a faulty motor?

Anyway, I only had a few minutes to play with an 70-400 on my A700 earlier this year and I didn't notice what you describe. I rather thought it focuses quickly.

Well if you make it focus with the cap on, it will move in both directions without finding any information before giving you the blinking green light...
Since it moves both ways at the same speed (faster speed than the one I described in my first post), I thought that I could rule out that the motor has a technical problem that makes it focus more slowly one way than the other...

But I am not too sure about this. I just compared it with my brothers 70-300G an that one seems more responsive..

I am waiting for some better wheather, it is very clouded and wet here, so not too much chance of trying it out in the field.

Thanks,
Jonathan

[Winston]

Hi there,

since the problems of the OP seem to be more or less solved, I hope you don't mind me "hijacking" the thread for a question concerning my own 70-400G, which I got yesterday:

When testing the lens in the shop, I noticed that the lens would not focus with the shop owners A350, my own A700 made it focus very, very slowly, especially when going from minimum distance to infintiy. The other way around is always faster.

I didn't buy that specific lens, we agreed it was faulty and he sent it back, he got me a new one in two days time:
It seems better, but the basic problem is still visible:

At longer focal lenghts (300-400mm) it has a lot more trouble to focus, especially when moving from minimum distance (1,5 m to infinity), it can take up to 3-4 seconds...
Of course the problem is more severe in suboptimal lighting conditions, but it is also noticeable in daylight.

Could somebody explain to me what happens when you zoom to 300-400mm? I always use the central AF-sensor (never learned to use the others) and I tried it with ans without the Tamron UV filter. Or is it just the fact that I expect too much or that the enormous magnification at 400mm gets the AF-sensor to read less contrast? I remember my Sigma 400/5.6 which was hunting like mad...

Anyway your help is greatly appreciated.

PS: I made the lens focus with the lens cap on. It focuses at the same speed in both directions which makes me rule out a faulty HSM motor.

Thanks in advance,

Jonathan

Mine takes longer to focus at the longer focal lengths too. As an old servo systems engineer, I'm not surprised.

I suggest using the the focus limiter; that's what it's for. Another thing I do is to manually set the lens at infinity. It's only a quarter turn to the right. It beomes second nature rather quickly.

Tip: The focus limiter is not a mechanical stop; so, you can leave it on all the time (I do). If your subject is very close, prefocus first...a quarter turn to the left will do it.

[Jonathan K]

Mine takes longer to focus at the longer focal lengths too. As an old servo systems engineer, I'm not surprised.

I suggest using the the focus limiter; that's what it's for. Another thing I do is to manually set the lens at infinity. It's only a quarter turn to the right. It beomes second nature rather quickly.

Tip: The focus limiter is not a mechanical stop; so, you can leave it on all the time (I do). If your subject is very close, prefocus first...a quarter turn to the left will do it.

Thanks, I believe that it is more or less normal. Nevertheless I am kind of upset to see that this lens needs enormous amounts of light to be functioning in an optimal way.

I will certainly try to use the focus limiter.

Cheers

Jonathan

[Heidfirst]

Nevertheless I am kind of upset to see that this lens needs enormous amounts of light to be functioning in an optimal way.

I don't think that it needs "enormous" amounts of light to work properly but any lens with a maximum of f5.6 (which it will be at at 300-400mm) obviously needs more light than e.g. f2.8 or f4.
Imo it's no worse than equivalent lenses from competing manufacturers & probably better than most.

[Winston]

Thanks, I believe that it is more or less normal. Nevertheless I am kind of upset to see that this lens needs enormous amounts of light to be functioning in an optimal way.

Mine does not need enormous amounts of light to function properly. I don't know what that's about.

[David Kilpatrick]

Just to clarify matters - unless a lens is f/2.8 or faster, and activates the central f/2.8 sensor, all the AF sensors in all current Sony models read the lens as if it had an aperture of f/7.1 (the only exception is the 500mm f/8 which has a special code to enable the central sensor only, and over-ride this).

So if you have an f/4, f/5.6, f/6.3 it makes no difference at all to the AF in terms of light level for a given condition. They all are seen by the AF sensors as if you had an f/7.1 lens fitted. Other things such as focal length and exit pupil size have subtle effects on how the AF works, but whatever the case is with the 70-400mm, any change in focusing ability as you zoom to 400mm is not down to the aperture change. It is probably caused by the focal length change.

Better light will still help of course, but helps all lenses equally (and those which are f/2.8 or faster, even more). Better light often also means better contrast and that can aid focusing.

David

[01af]

At longer focal lenghts (300 - 400 mm) it has a lot more trouble to focus, especially when moving from minimum distance (1.5 m to infinity), it can take up to 3 - 4 seconds ...

Yes, that's normal with this lens. When the AF starts at a setting very far off the actual subject distance then it takes a few additional seconds to sort things out. SSM is not particularly fast in that case, so I have the focus limiter on almost all the time. However I wouldn't call it "trouble" ... it just takes a few extra seconds.

SSM is fast---and accurate---when it comes to adjusting for small focus shifts.

-- Olaf

[stevecim]

I got a new filter today. They have exchanged it without any problems. They also ran some test, and it was remarkable to see the difference. The problem is not that obvious shooting subjects 5-7m, but going futher 10-20m the results are shocking!

At least I know now how to test focus, back focus and I have met the head technician of Sony South Africa. I guess it was all worth it.

Thanks for the help.

Can you please post some 100% crops , I would love to see the differance?

Cheers Steve

[Jonathan K]

Just to clarify matters - unless a lens is f/2.8 or faster, and activates the central f/2.8 sensor, all the AF sensors in all current Sony models read the lens as if it had an aperture of f/7.1 (the only exception is the 500mm f/8 which has a special code to enable the central sensor only, and over-ride this).

So if you have an f/4, f/5.6, f/6.3 it makes no difference at all to the AF in terms of light level for a given condition. They all are seen by the AF sensors as if you had an f/7.1 lens fitted. Other things such as focal length and exit pupil size have subtle effects on how the AF works, but whatever the case is with the 70-400mm, any change in focusing ability as you zoom to 400mm is not down to the aperture change. It is probably caused by the focal length change.

Better light will still help of course, but helps all lenses equally (and those which are f/2.8 or faster, even more). Better light often also means better contrast and that can aid focusing.

David

Thanks for the info, David. Maybe I haven't been too clear in my post, but I never wanted to suggest that there was a relation between aperture and the phenomenon I experience, but rather the focal length. There is a very quick and abrupt drop in focus speed, once you reach the 300mm.

Since there are other, more experienced users who notice the same thing, (thanks to all for your reply), I suppose I can rule out that there is something wrong with this particular sample.

So what I would like to know: Why does that happen? What influence does the focal lenght have on the way the AF-sensor reads the information? (since the information remains roughly the same... between 290mm and 310mm for example)...

Today I believe I have the opportunity to take some action shots... there is a boat race down the river in town.I will see if I can get a few "test shots".

Thanks, Jonathan