The magnification depends not only on the focal length of the lens and the length of the tubes, but also how close the lens will focus in the first place. If you have a 100mm lens that focuses to 1.0m and a 100mm lens that focuses to 0.8m without tubes, then the one that focuses to 0.8m will produce a larger image both with and without tubes. I know this doesn't really answer your questions, but it's not a simple relationship between focal length and image size!!

Regards
David

That lens looks like one heck of a sharp piece of kit Gary. The focus on these shots is stunning and they also seem to have a fair amount of Depth of Field. Some of the best Dragonfly / Butterfly shots I've seen in a while.

Regards
David

Thanks all for your guidance! I'll make sure I stick within the rules!

Regards
David

Hi Chris, great macro of the ladybird there! Standard lenses with extension tubes can often take better macro shots than dedicated macro lenses, however they are clearly not as easy to use. I find that with a standard 50mm (mine is a Chinon F1.9), the depth of field is absolutely minute, whereas with my Sigma 50mm Macro, there's a bit more depth to play with. However, the Chinon takes nicer images and has better out of focus effects so I suppose it's horses for courses.

I also like to use longer primes with extension tubes - I have had good results with a SMC 135mm Takumar and a 200mm Tele-Takumar F5.6 which can produce more magnified images than the 50mm Chinon.

Well done with your first macro attempt and keep up the good work!

Regards
David

Just a quick question, I'm probably being stupid, but do the entries for the weekly competitions have be shot within the competition time period?

I thought they did, but I've had a look at this week's and some were shot earlier?

Also, can you only upload one picture per competition?

Thanks in advance of any help given.

Regards
David

Fabulous lens for the money - you will not buy better. The only caveat is that it is noisy in AF and can be a bit tricky to lock onto small subjects (especially in dim light), however, unless you intend to use for sports or for close shots of wildlife this should not be an issue. BTW, it focusses much faster / better on my K-5 than it does on my K-x.

Image quality is superb - I use it quite often for landscapes at its shortest focal length.

Regards
David

I am using an old (5 yrs-ish) Pentium D Dual Core 3Ghz with 3Gb RAM running Windows XP and with an old-ish Nvidia 8600GT graphics card with 256mb of graphics RAM. Disks are 2x 2TB Network Storage Devices which are automatically sychronized using a freeware program called Allway Sync (which is very good BTW).

Everything flies on this setup except for the boot-up time (PC needs cleaning up a bit) and the file save/load because this is being done over a network. There's no need for anything more powerful as others have stated here unless you are working with 3D applications. Best advice would be get a decent mid-range processor, bang in as much fast RAM as the machine will take and fit the fastest disks you can (RAID array is good). It's the memory and disks that are most critical.

Regards
David

Hi Dan, welcome to Pentax! Not sure if you have one of the Chinon 50mm F1.7 or F1.9's, but if so they are great! I use my F1.9 a lot on the K-x and K-5 and it produces wonderful images.

Regards
David

I have tried the K-5's in-camera HDR today on a fairly weak setting and it works pretty well. It is clearly not as effective as careful processing in Photomatix, but used on a low setting it looks natural and significantly increases dynamic range.

I agree with the comments above about careful use of HDR - the results should look real and natural - too many are over-processed and full of image noise.

Regards
David

Matty, there is no difference in the optical quality - all versions of this lens use identical glass.

Regards
David