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05-04-2011, 07:03 PM   #1
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What mm do set my camera to when using Tameron 500mm ??

I have a Tameron SP 500mm mirror lens, and i know when you put older lenses without contacts into the camera you must manually select the mm size in the camera when you turn it on.

What setting should i use for my K-x? I know that lenses made for film have a different effect on digital cameras.

This setting affects how the shake reduction works i believe right? Maybe thats why the pictures arnt as sharp as they could be? I have no problems when using auto lenses.

PS. What would i set the camera to when using an old 50mm prime?

05-04-2011, 07:07 PM   #2
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Set it to the actual lens focal length or the nearest value when using lenses that do not send that information to the camera. Focal length is focal length.


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05-04-2011, 07:20 PM   #3
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So even though the lens was made for a film camera i would still set the camera to the focal length thats on the lens?

I thought that lenses made for film cameras functioned different with a digital sensor camera?

Like a 50mm lens would be closer to a 32mm on digital, or something like that.
05-04-2011, 07:24 PM   #4
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A 300mm lens is a 300mm lens, regardless of the camera it's mounted on. However, a 300mm lens on an apsc digital camera will have a field of view similar to a 450mm on a 35mm film camera. The focal length however stays the same.

Think of it this way: on a digital camera it's like it's cropped 1 and a half times.

05-04-2011, 07:30 PM   #5
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Use the actual lens mm length. The crop factor for digital is only to give you a reference to the amount of the scene you will capture compared the film or a full-frame sensor.
And, the lens size setting on the camera is only to assist in SR. If you put your 500mm on a tripod then it really wouldn't matter what size was set because you should turn off the SR anyway.
05-04-2011, 07:45 PM   #6
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Your main question has been answered, but there is one addition I'd like to make that might help..

QuoteOriginally posted by Silverkarn Quote
Maybe thats why the pictures arnt as sharp as they could be?
Softness at long focal lengths could be due to mirror slap - try using mirror lock-up (and maybe a tripod and remote shutter release) to see if it helps.
05-04-2011, 07:49 PM   #7
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As mentioned, focal length is focal length. A 100mm lens remains a 100mm lens regardless of whether it's on a Fuji 6x9, Hasselblad 6x6, Pentax 645, Minolta FF, digital APS-C (like your dSLR), Olympus m4/3, Bolex 16mm, or anything else. Smaller frames (film or digital) just see less of the projected image.

Also as mentioned, turn SR off when using a tripod. SR is for handheld non-macro shooting. A stabilized camera with SR on gives shaky pictures. SR doesn't help with very close shots because your shaky motions are in 3 dimensions while the SR correction is only in 2 dimensions. If you use a timer or remote mode, the camera shuts-off SR anyway.
05-05-2011, 07:47 AM   #8
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Well, I was using 1/300 shutter speed, handheld, with my hand holding the camera braced on a wall corner and the image was still blurry enough that you couldn't see detail when viewed at 1:1 size on photoshop.

05-05-2011, 03:49 PM   #9
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1/300" would be quite iffy for a 500mm lens. The old rule of thumb of aiming for a shutter speed 1 / (35mm equivalent focal length) would suggest you should have been shooting a stop and a half faster. I don't think you can trust your wall bracing and SR to give enough improvement at that focal length to guarantee the sort of sharpness that would stand up to 1:1 viewing. And while the Tamron is considered one of the best of the mirror lenses, it's also unreasonable to expect them to have the same resolution as, say, a 50mm lens. Finally, realize that DOF at 500mm and f/8 is usually only a matter of inches, and with the darkness of the viewfinder image (due to being f/8 and the obstruction within the lens and the loss of light due to the primary mirror), it's notoriously difficult to get exact focus with a mirror lens.
05-06-2011, 01:29 AM   #10
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Actually it's an interesting thought. Although a focal length is a focal length, wouldn't the shake observed by the sensor will be more in the center part compared to a full frame.
05-06-2011, 02:18 AM   #11
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QuoteOriginally posted by Marc Sabatella Quote
it's notoriously difficult to get exact focus with a mirror lens.
Which is why I put metal tape on my Sakar 500/8's T2-PK base and always use CIF with it. And use it in bright light. I just did some shooting in a downtown and got some very nice results with brightly-lit targets.

QuoteOriginally posted by yusuf Quote
Actually it's an interesting thought. Although a focal length is a focal length, wouldn't the shake observed by the sensor will be more in the center part compared to a full frame.
The SR system in my K20D doesn't care what camera format a lens was designed for, nor how it is built, nor how it is being used. If I build a 35/0.9 lens by stacking +30 dioptre closeup lenses on a focusing helicoid and enter 35mm, it's stabilized (but soft). If I put 60-75-90-105-127-140-162mm enlarger|projector lenses on bellows and enter the closest FL, they're stabilized. If I put MF lenses on adapters and enter the FL, they're stabilized. If I put a 12-inch LF lens on extension and enter 300mm, it's stabilized (but heavy). If I reverse an A35-80 zoom, set to 75mm and I enter 75mm, it's stabilized. ONLY THE FOCAL LENGTH MATTERS!
05-06-2011, 03:19 AM   #12
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QuoteOriginally posted by RioRico Quote
Also as mentioned, turn SR off when using a tripod. SR is for handheld non-macro shooting. A stabilized camera with SR on gives shaky pictures. SR doesn't help with very close shots because your shaky motions are in 3 dimensions while the SR correction is only in 2 dimensions. If you use a timer or remote mode, the camera shuts-off SR anyway.

So this is why there are no macro lenses with SR except for the Canon 100mm IS macro?

Is there any specific difficulties if I use my Sigma macro with the K-x SR on?

Seb.
05-06-2011, 07:58 AM   #13
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QuoteOriginally posted by yusuf Quote
Actually it's an interesting thought. Although a focal length is a focal length, wouldn't the shake observed by the sensor will be more in the center part compared to a full frame.
I don't understand the question exactly, but I'd have no trouble believing that if you were designing an SR system, you'd probably want to know the size of the sensor you were moving around. But I'm pretty sure the designers of Pentax SR system know they are dealing with an APS-C sensor. So even if the system has to take this into account, it would be crazy to assume they wouldn't have done so.

The confusion comes from the completely misguided notion that focal length on a lens designed for film means something different from focal length on a lens designed for digital. For some reason get the idea that crop factor is something you use to compare *lenses*, when in fact, it's something you use to compare *cameras*. All 500mm lenses have the focal length and will produce the same image on *a given camera*, whether the lens was designed for film or digital. However, any given 500mm lens will produce different images on an APS-C versus FF camera.
05-06-2011, 11:49 AM   #14
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Marc said it perfectly. The only differences between lenses designed for digital vs designed for film are:
1) Image circle coverage.
2) Minimum standards for antireflection coatings due to digital sensors being more reflective than film sensors. Film is more forgiving of subpar lens coatings.

However, focal length wise - as said before, focal length is focal length, a 500mm lens is always a 500mm lens regardless of what camera it was designed for.
05-07-2011, 12:27 PM   #15
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I follow the point of the FL being what it is but the old rule of thumb of 1/FL for a speed guide should surely be 1/1.5FL for an APS-C DSLR because the FOV on the sensor is as if one is using a lens that magnifies an image 50% more than if that lens is being used on a 35mm frame size camera.

I've read many times, for instance that a 300mm lens on an APS-c camera produces an image equivalent to a FF camera with a 450mm lens.

Assume for the sake of argument that a 1mm sideways displacement of the camera takes place during a shot. On a FF sensor the movement blur is x% of the width of the sensor but on an APS-C sensor, the movement blur will be 1.5x% of the width of the sensor. To reduce the blur width to the same % as on a FF sensor, the shutter speed needs to be 1.5x faster than what is being used on the FF camera.

Since the Pentax antshake system gives at best a two stop advantage, in the hands of an experienced picture taker, using a 300mm lens implies that one would seldom get a blur free picture, hand held, with speeds slower than 1/120.

With a 500mm lens, the hand held speed guide should be 1/200s or faster.

With the kit lens at 18mm, one should be OK down to 1/10s and in some cases, 1/5 but unlikely to be consistent at that speed.

This is a rule of thumb and there are some real steady shot Sams out there that can do better than this but for beginners and weekend shooters, these guidelines are worth remembering.
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