Extension rings with Digital Pentax.

I'm not up on these. Would they work with a digital camera. I can't make much sense of my manual. Would it work in Av with the aperture at max??

Any tips welcome.

Yes, I've used Pentax auto extension tubes on the *ist-D. However, you have to do things manually (of course). Open the lens wide, focus and frame, stop down and meter.
(You also have to enable the custom function that lets the shutter fire when the lens is not in the A position )
Had some pretty excellent results with an SMC-F 50mm/f1.7 and tubes
Matt

Thanks for that. So to sum up;
If I have a lens with an Aperture ring it will work but for auto lenses the connection for changing aperture is lost.

Hmmm!

Hi,
I think this is the reason the more recent AF Macro lenses focus up to true life size. All the MF ones and the 100/3.5 only went to 1/2 life size without a tube. I guess some of us Luddites still using MF and film have the odd advantage

Kim

Yes, it is for genuine Pentax tubes. However, I picked up some cheap third party tubes from a Jessops branch that have the electrical contacts so the fully automatic aperture features are kept So I only lose autofocus, which isn't much use in macro anyway.

Tubes work well, the SMC-F 100mm/f2.8 is beautiful and better, and with the SMC-F 1.7xAF convertor too you get really close
Matt

Matt, I think you have confused the issue here.

Extension tubes on digital SLRs work exactly as they do on film SLRs.

If they are AUTO tubes, then you can use whatever exposure mode you like on the D or DS. If they are manual tubes, then of course they must be used in manual mode.

G

George,
Thanks. I'm not completely confused.... at least I don't think so! LOL!

Please note that the "Pentax Auto Extension Tubes" are only auto with the older bodies - it used the "finger" to mechanically sense the aperture, rather than electronics. With those on the *ist-D/DS you can only use them as manual (now that sounds more confusing that it is!!).

It's only the third party tubes that have the electrical connections that will, as you say, give you auto on the *ist-D/DS.

Matt

Matt,

My apologies. It seems you are better informed than I am. My tubes aren't Pentax, so I wasn't aware that the Pentax ones are "crippled".

G

George, no apology needed Just like to clarify things.

Well I think I'm more confused than ever now. I didn't know you could get ones with the electrical connections. I'll call in at Jessops and enqure. Thanks for all the replies.

Hi,
I suspect that the reason Pentax have not produced electrical or AF auto tubes is that there is little or no reason for them. If you want quality, a macro lens is better. The AF lenses focus to life size without the need of tubes. Once you enter the realms of true macro work ie greater than life size you really need bellows and to be able to reverse the lens.

Any lens is designed such that it performs best when the light path on the object side is at a shallower angle then the light on the film side. At greater than life size this is not the case so reversing the lens restores the staus quo. It is also better at these magnifications to use a focus rail. In other words you set the magnification on the bellows and then focus by moving the whole setup back and forth. Autofocus would be useless. Depth of field is critical and exposure compensation becomes important. The purpose of the electrical contacts is the provide max and min apertures for the program and shutter priority modes. At best you will use aperture priority and probably manual metering or OTF flash.

The only purpose, therefore, for fully auto tubes would be to try and get closer with a non macro lens but not life size. For this I would recommend the 1.7AF convertor as Matt suggests. With the lens at infinity you get the same closefocus point but because of the apparent longer length you will get greater magnification. If you then set the lens to it's close focus point, it gets even better. Also by giving you a longer focal length you are further away and the lighting becomes that much easier.

In summary, for AF, if you want good quality closeups, use a true macro. The next best thing is a prime lens on the 1.7x convertor. If you want to get really BIG, go for a bellows. If necessary, pick up a cheap MF body for this.

Regards
Kim

Matt,

My brain works better in the morning. I think what you are saying is that when using the Pentax tubes on a D or DS, you set the aperture you want to use on the lens, set the camera to manual, and meter the way you do with K or M lenses.

When you press the shutter, the tubes will stop the lens down to the pre-set aperture, and you will have a correctly exposed picture.

It's basically exactly like using a K or M lens.

G

George,
Yes, I think so. I had the Pentax manual tubes which meant that adjusting the aperture on the lens stopped it down. Everything was done manually, yes, like using an M series lens.
Matt

Enough! One is doing my head in... I was looking for a cost effective way of experimenting with close up photography. I think the safest way to go is to go straight in and get a dedicated Macro lens and then work out what you've been discusssing later....LOL
Thanks though.

Downswood,

Looking back at your original question, you asked: "Would it work in Av with the lens set at max aperture?"

The answer is yes (even for the Pentax tubes).

However, this is probably the last thing you would want to do. Macro photography is all about capturing fine detail. This is not compatible with full aperture, which tends on most lenses to be rather soft.

Furthermore, because depth of field is very restricted at close range, most macro photographs are taken with the lens set at a small aperture.

However, it is usually the case in macro photography that you have both time, and control over light. This means that operating in manual exposure mode is no great hardship, especially with digital where you can experiment until you obtain perfect exposure.

Since you are looking for a cost-effective way into macro, I think tubes will be a good start. I use them on my FA 1:2.8 100mm macro when I want to get even closer, so buying a macro lens doesn't mean the tubes are redundant. And you can of course use them on all your lenses.

Kim, of course, is absolutely right in saying that a dedicated macro lens is the best solution, but the best solution is rarely cheap. Having said that, the M macros are not too pricey, but they are MF lenses, and they don't offer Av on a DSLR. If you want to play safe, and don't mind spending money, buy an F or FA 100mm, and you can use it as a very sharp short tele for normal purposes.

George