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03-31-2008, 10:44 PM   #1
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using Pentax smc 300 f/4 with K20D

Sorry for some basic questions here. I have had almost no experience with older, non-digital, non-auto-focus lenses.

I just received the Pentax (Asahi) smc 300 f/4 lens from KEH. I'm pretty sure that's the correct name or designation for the lens; doesn't seem to be part of any lens series like DA, FA, etc.

I know basically how to configure the camera to use this lens. When I started up the camera after installing the lens, I selected 300mm as the focal length for shake reduction. And then I set the last custom setting to allow use of the aperture ring. I was able to take a couple quick test photos in my back yard that aren't too bad.

I'm wondering about a couple of things, though.

First, it appears that I can't use the camera's meter with this lens. Is that right? It's not a huge problem, I'm just asking. If this is right, then I'll just use the depth of field preview to test the exposure, eyeball the histogram and make a quick adjustment. I've shot manual so long I can usually guess an acceptable exposure pretty closely anyway, and I can fine tune if necessary. Still, if I'm missing something about metering, I'd like to know.

Second, is there any reason that I should NOT use my Tamron 1.4x teleconverter with this lens? I'm fairly nervous about incompatibility problems and I'm timid mixing brand X with brand Y when I don't know for sure that the mix is safe. Would this be safe?

Third, if I wanted to try this with a 2x teleconverter, what would be the best one to get? I had a Kenko 2x for about 24 hours a year ago. Can't even remember why I sent it back.

Fourth and finally, I am pretty sure that somewhere recently I read a comment that made me think there's a way to get auto-focus to work with this lens, perhaps with the use of a teleconverter or some other adapter. Am I dreaming that or is it true?

Autofocus would be nice, but not essential. I'm ordering another Katz Eye for my K20D and it will be very useful with this lens. I notice that the focusing ring on the barrel seems a bit stiff, but I'll get used to it.

Thanks in advance,

Will

03-31-2008, 11:00 PM   #2
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QuoteOriginally posted by WMBP Quote
Sorry for some basic questions here. I have had almost no experience with older, non-digital, non-auto-focus lenses.

I just received the Pentax (Asahi) smc 300 f/4 lens from KEH. I'm pretty sure that's the correct name or designation for the lens; doesn't seem to be part of any lens series like DA, FA, etc.

I know basically how to configure the camera to use this lens. When I started up the camera after installing the lens, I selected 300mm as the focal length for shake reduction. And then I set the last custom setting to allow use of the aperture ring. I was able to take a couple quick test photos in my back yard that aren't too bad.

I'm wondering about a couple of things, though.

First, it appears that I can't use the camera's meter with this lens. Is that right? It's not a huge problem, I'm just asking. If this is right, then I'll just use the depth of field preview to test the exposure, eyeball the histogram and make a quick adjustment. I've shot manual so long I can usually guess an acceptable exposure pretty closely anyway, and I can fine tune if necessary. Still, if I'm missing something about metering, I'd like to know.
No, that is untrue. To use the lens on your camera, you need to use manual exposure metering. My preferred system is to use the Optical Depth of Field Preview on the power switch, and change the shutter speed to match meter the +/- exposure display. It might be that the lens will not meter accurately wide open. My 400, for example, overexposes when I meter wide open, but if I meter between f/8 and f/16, I get an accurate reading. I can then interpolate from there. Another way of doing this is to set the preferred aperture and then press the green button on the camera top. The camera will then set a shutter speed appropriate to the aperture you have set. With my K10D and the 400, I can use this system between f/8 and f/16, but not outside this range.
QuoteQuote:
Second, is there any reason that I should NOT use my Tamron 1.4x teleconverter with this lens? I'm fairly nervous about incompatibility problems and I'm timid mixing brand X with brand Y when I don't know for sure that the mix is safe. Would this be safe?
I do not have the Tamron, but it should work fine with the lens. You definitely will not damage the lens or the teleconverter by using it. Take some images and examine them closely in post processing, then decide whether or not to use the combination. Your lens is old enough that chromatic aberration is probably there, and the TC will multiply the width by 1.4 along with the rest of the image. To offset this, you are using only the center portion of a full frame 35mm lens.
QuoteQuote:
Third, if I wanted to try this with a 2x teleconverter, what would be the best one to get? I had a Kenko 2x for about 24 hours a year ago. Can't even remember why I sent it back.
Whichever converter you get, make sure it is the top quality converter. An inexpensive converter will degrade the image pretty badly.
QuoteQuote:
Fourth and finally, I am pretty sure that somewhere recently I read a comment that made me think there's a way to get auto-focus to work with this lens, perhaps with the use of a teleconverter or some other adapter. Am I dreaming that or is it true?
You are not dreaming. Unfortunately, there is only one converter that will do that, and it is the Pentax 1.7X AF. The converter will autofocus, but within a limited range. The operating method is to rough focus manually, then it will adjust the focus more finely. I have one en route, and will learn how to use it when it gets here.
QuoteQuote:
Autofocus would be nice, but not essential. I'm ordering another Katz Eye for my K20D and it will be very useful with this lens. I notice that the focusing ring on the barrel seems a bit stiff, but I'll get used to it.
When you put in your Katz Eye, you might have exposure changes with the DA lenses you have. You will need to find out what EF to apply to correct this.


Thanks in advance,

Will[/QUOTE]
04-01-2008, 08:02 PM   #3
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Will, As I don't have a K20D I will make a quantum leap of imagination here and assume it has similar controls to the K10D and *istD

Specifically dual thumb wheels and a green button, plus DOF preview and meter activation as an extension of the on off switch.

If this is the case, you can either press the green button, and have the camera set the shutter speed to match your apature and ISO, or you can activate teh DOF preview, at which point th emeter activates and you can manually adjust either apature via the apature ring or shutter speed with the fring wheel.

What would be interesting is how the K20 meters with manual apature lenses. You know my reported behavior on the K10D which is suspect,

Also, the SMC 300F4, in not having information contacts on the mount, will not work with P-TTL flash, but If I recall correctly you have an AF540FGZ, which can work in auto mode using the flashes photo sensor. If you kept your DS, the AF540FGZ will work in TTL mode with the 300mm on that body

As for the TC's, all you need to do is check that the tamron does not have any interference between the back of the 300mm and the front element of the tamron. It is the sigma TCs that really have an issue with this,

If you want a really nice setup, don;t go for a 2x, but go for the SMC-F 1.7x AF TC. this will give you an element of autofocus after you get close with MF.

That is how I use my 300mm F4

Last edited by Lowell Goudge; 04-01-2008 at 08:29 PM.
04-01-2008, 09:20 PM   #4
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QuoteOriginally posted by Lowell Goudge Quote
Will, As I don't have a K20D I will make a quantum leap of imagination here and assume it has similar controls to the K10D and *istD

Specifically dual thumb wheels and a green button, plus DOF preview and meter activation as an extension of the on off switch.
Lowell,

Yes, the K20D is virtually identical to the K10D on the outside - including the dual e-dials and the depth of field preview switch.


QuoteQuote:
If this is the case, you can either press the green button, and have the camera set the shutter speed to match your apature and ISO, or you can activate teh DOF preview, at which point th emeter activates and you can manually adjust either apature via the apature ring or shutter speed with the fring wheel.
That's what I've been doing - basically, making a guess and then testing it either by simply taking a picture (if my guess is right, then I'm done!) or by using depth of field preview and eyeballing the histogram, then adjusting.

If the subject is standing relatively still, like the whoopers, then this will work okay. But it's not going to be ideal for those times when the subject is on the move and I have to act quickly. And that happens a fair bit. Got photos of a red-tailed fox a couple of years ago who appeared out of nowhere in the mountains, ran alongside my car for 50 ft, then ran off into the woods.

Which is why I'm second-guessing myself about this lens. I may send it back. Of course it's a stop faster at 300mm than my Tamron 70-300 Di LD (f/4 for the Pentax, f/5.6 for the Tamron). And it may be slightly sharper, too. But my test photos today reminded me that it's advantage in terms of image quality over the Tamron isn't overwhelming. I lose also the zoom capability. And as you know, it weighs half a ton! So I'm still thinking about it.


QuoteQuote:
What would be interesting is how the K20 meters with manual apature lenses. You know my reported behavior on the K10D which is suspect,
Right, I remember. I haven't taken quite enough photos with the Pentax 300 to have figured out if it has any idiosyncrasies. The K20D is supposed to meter a little better, I think, than the K10D.

Problems with flash don't bother me right now. I'm not going to be using flash with any long lens. I know that you do, but I shoot wildlife almost entirely in available light. I say "almost entirely," because I did photograph a screech owl in our yard using a flashlight, but that's rare.

QuoteQuote:
If you want a really nice setup, don;t go for a 2x, but go for the SMC-F 1.7x AF TC. this will give you an element of autofocus after you get close with MF.

That is how I use my 300mm F4
Ah, so it was you who mentioned this converter. Do you know if it's available anywhere? I've been looking for it today but without success.

I assume a 1.7x converter would cost, oh, one and a half stops?

Thanks,

Will

04-02-2008, 06:36 PM   #5
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QuoteOriginally posted by WMBP Quote
Lowell,

Yes, the K20D is virtually identical to the K10D on the outside - including the dual e-dials and the depth of field preview switch.


That's what I've been doing - basically, making a guess and then testing it either by simply taking a picture (if my guess is right, then I'm done!) or by using depth of field preview and eyeballing the histogram, then adjusting.

If the subject is standing relatively still, like the whoopers, then this will work okay. But it's not going to be ideal for those times when the subject is on the move and I have to act quickly. And that happens a fair bit. Got photos of a red-tailed fox a couple of years ago who appeared out of nowhere in the mountains, ran alongside my car for 50 ft, then ran off into the woods.
I know, I think it is 270 degrees lock to lock on the focusing. you should try my vivitar 400, 330 degrees
QuoteQuote:
Which is why I'm second-guessing myself about this lens. I may send it back. Of course it's a stop faster at 300mm than my Tamron 70-300 Di LD (f/4 for the Pentax, f/5.6 for the Tamron). And it may be slightly sharper, too. But my test photos today reminded me that it's advantage in terms of image quality over the Tamron isn't overwhelming. I lose also the zoom capability. And as you know, it weighs half a ton! So I'm still thinking about it.


Right, I remember. I haven't taken quite enough photos with the Pentax 300 to have figured out if it has any idiosyncrasies. The K20D is supposed to meter a little better, I think, than the K10D.

Problems with flash don't bother me right now. I'm not going to be using flash with any long lens. I know that you do, but I shoot wildlife almost entirely in available light. I say "almost entirely," because I did photograph a screech owl in our yard using a flashlight, but that's rare.

Ah, so it was you who mentioned this converter. Do you know if it's available anywhere? I've been looking for it today but without success.

I assume a 1.7x converter would cost, oh, one and a half stops?

Thanks,

Will
Will the TC does cost 1 1/2 stops, but you get a 510mm F6.7 or something like that. It is only marginally slower than a bigma. There was one in the market place last week. they are going for very high prices, 300-400 US from memory


I notice you liked Ben's mirror. They are light, but I don't know if they are any faster to focus. Perhaps you should ask ben about the lock to lock focusing .

ps.\

speaking of whoopers

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