Queston??
 

Okay, I've been doing some reading, and playing on the sim-cam website. It started me thinking, My sigma 50/500mm lens is F4-6.3. Should I set my D50 up for an aperture of 6.3 since that is the opening (aperture?) that the lens will be? Then adjust to a slower shutter speed to compesate for the small aperture? Or do I still not have my think straight?


Thanks,

Frank
www.decoysbyfrank.com

Hi Frank, your lens is marketed as f4-6.3, this is the largest aperture this lens will go. As the aperture is relative to the focal length, and the lens is a zoom lens (variable focal length), the aperture is shown as a range. The biggest your lens will go at the 50mm end of the zoom is f4, by the time it's got to the 500mm end, that equates to f6.3.

If you leave the camera on auto program, it will adjust the aperture to whatever setting it thinks is best for the amount of light available. This may, or may not, be the widest the lens will go.

If you use manual mode, or aperture priority, and set the camera to f4 (at the short end) or f6.3 at the long end, the aperture will be at its widest and you will get the fastest shutter speed possible under the lighting conditions you have (unless you adjust the ISO 'film' speed).

Hope this makes sense.

Duncan

Thank for the reply
 

I forgot to mention that since my main interest in picture taking is waterfowl I expect to always be shooting at 500mm or more(since I have a 2x converter?) I was under the impression that since the lens is going to be at F6.3 or F8 (converter attached) the camera should be too.

Frank

The lens will be at whatever you or the camera set it to, it has a variable aperture. If you set the camera to f16 (for example), the camera will set the lens to f16. The aperture of the lens is dictated bythe camera or the user (you). The limitation to this is that the aperture cannot go bigger than the figures specified by the lens manufacturer.

Als oremember that if you are using a 2x teleconvertor, that will reduce the maximum effective aperture of the lens by two stops. At the long end of the zoom range (f6.3 without convertor) will actually be something like f13. You will have serious problems with auto-focus not having enough light/contrast to work effectively with this aperture.

Regards,

Duncan

Thanks Duncan
 

The Sigma loses auto focus capability when the converter is attached. I have realized that exposure time (shutter speed) will need to be slow when using the converter, in order to allow enough light penetration into the camera. I just wasn't sure if I should match the camera and the lens Fstop. To make an anology "the right size screw & thread to the right size nut". As you can tell I'm really green at photograpy.

Thanks for your patience and help, one and all!

Frank

Hi Frank

Seems strange that Sigma have only produced a TC that offers MF for its APO range of lenses.

Have you enquired as to whether the Nikon TC 2E11 range will afford you AF and metering service on your lens, as these duplicate the pin sequence from the camera functions on the Nikon.

The lack of AF isn't down to the TC not being capable of talking to the camera, but due to the 2 stops of light reduction you get with a 2x TC. This reduces the max effective aperture to something so dim there isn't enough contrast in the resulting image for the AF to lock onto.

If this TC was used with a f1.4 50mm prime lens then the AF would work fine.

Duncan

lenses/converters
 

I have tried to fit the Sigma converter onto my Nikon/ Nikkor lenses. The converter does not seem to want to fit. I don't want to force it and cause myself more headaches. The fit is so close it feels like it wants to go, but I think the difference is measued in thousandths of an inch.

While were on the subject of 500mm lens and converters, do you more expieranced photographers think I will be able to get some decent shots at full magnification? I'm not looking to publish to the National Geographic mind you. I just want some decent reference shots to help me carve a decoy. In decoy competition judges can be brutal if you miss an obvious trait in the species carved.

Frank

My Nikon TC's the 1.7 and 2 work on all the AFS lenses I use from the 70-200AFSVR through all the Primes from 200 and the AFSVR 200-400 from max aps of f2.8 - min f32 giving full support on AF and metering regardless of the aperture setting.

Whaooo
 

What did you just say? Remember I just a new "kid" learning this stuff. What are all those letters and what do they mean? AFS lenses (auto focus "S" ?)- 200AFSVP (200mm-auto focus- SVP??) max aps (max apertures?).

Ok I get that your nikon TC's work OK, it's my Sigma TC that doesn't want to fit my Nikon lenses.

Frank

That's because you may have set the aperture on the camera to take the picture at f32, but when the camera is taking its metering readings and performing AF, it will have the lens wide open, not at the final intended aperture.

If you have a Depth of Field preview function try this experiment:
Set the aperture to f32 using aperture priority or manual mode.
Look through the viewfinder without using Dof preview.
Press the DoF preview button, watch the viewfinder go dim, very dim.

The viewfinder screen is normally viewed with the aperture wide open, the camera performs AF in this mode. When the DoF preview button is pressed, the camera stops the aperture down to the intended final setting so that you can see the resulting DoF in the viewfinder. When taking the picture, the camera does not actually stop down the aperture until the shutter release button has been pressed. If the camera varied the aperture directly as the aperture setting was adjusted on the camera, it would be possible to see the DoF varying as you made the adjustment, it would also be clear that the brightness of the image in the viewfinder was changing as you varied the aperture. Neither of these effects are seen when not using the DoF preview function.

When performing AF and letting the camera change its focus point, you do not see the brightness of the image in the viewfinder vary, nor do you see the DoF vary, this is because the AF is performed with the lens wide open. If you stick on a 2x TC to a lens that has a max aperture of 6.3 it is unlikely to AF unless the subject is exceptionally bright and contrasty, the max aperture just isn't enough for the AF sensor to work with under most circumstances. Unless you have an extremely bright subject with lots of contrast, AF will struggle if presented with a smaller effective aperture than f8 when wide open.

Sorry Frank

Did not mean to confuse you –I was answering Duncans last post.

Duncan is correct in what he says – my confusion arose because all my lenses are f2,8 or f4 all the way through so even with a 2TC the worst would be f8. As he quite rightly says, at your 500mm end you have f6.3 less 2 stops for your TC.

I have been to a few Sigma 50-500 review sites and it looks as though with the Sigma TC2 you have to go completely Manual.

Brian