Go Back   Steve's Digicams Forums > Digital SLR and Interchangeable Lens Cameras > Pentax Lenses

Reply
 
Thread Tools Search this Thread
Old May 24, 2008, 10:40 PM   #1
Senior Member
 
Rodney9's Avatar
 
Join Date: Nov 2006
Location: Yeronga, Brisbane, Queensland, Australia
Posts: 3,518
Default

Hello,

I have a Pentax K100D and I recently bought a Pentax-M 100mm F4 Macro. I would like to test and compare it to my Tamron SP AF90mm F/2.8 (Di) Macro and show the results here.

What would be the best way to go about this, just two simple photos or several at different settings or what ?

Any advice would be appreciated,
Rodney.
Rodney9 is offline   Reply With Quote
Sponsored Links
Old May 25, 2008, 2:15 AM   #2
Senior Member
 
bilybianca's Avatar
 
Join Date: Nov 2005
Location: Hassleholm, Sweden
Posts: 3,435
Default

My way of thinking about this is to get it as "all else equal" as possible. Any difference in the pictures should be due to differences in the lenses.

a) Use a tripod and 2 sec delay, mirror lockup. SR off.

b) Bring paper and a pencil. Take notes about every setting for every shot. In front of the computer you'll need those notes.

c) Be sure to take all the shots within as short a time as possible, if your not in a studio with totally controlled lighting conditions. If you're outdoors the sun goes higher or lower., clouds might come and go.

d) Take the shots of something stationary, like a flower.

e) Use various settings. If you don't, you'll regret that afterwords when you sit there and wonder "hmmm, how would they compare at smaller apertures". Setting everything up is much more trouble than clicking away a few more pictures. You don't have to use all the pictures if you don't see anything interesting to report, but at least you have them.

There are test charts, but I actually prefer test shots of "real" subjects. The evaluation is subjective anyway. I think the test should be performed to help people decide which one they prefer, not to "objectively" decide which one is "the best".

I'm in no way a scientist and have only performed a few tests myself, so take my advice for what they are worth. (One of my tests is found here: http://forums.steves-digicams.com/fo...=80&page=2)

Kjell
bilybianca is offline   Reply With Quote
Old May 25, 2008, 8:23 AM   #3
Senior Member
 
danielchtong's Avatar
 
Join Date: Dec 2005
Posts: 2,888
Default

Rodney9 wrote:
Quote:
Hello,

I have a Pentax K100D and I recently bought a Pentax-M 100mm F4 Macro. I would like to test and compare it to my Tamron SP AF90mm F/2.8 (Di) Macro and show the results here.

What would be the best way to go about this, just two simple photos or several at different settings or what ?

Any advice would be appreciated,
Rodney.
Kjell more or less has summarised what I am saying. Also compare the non-macro shots of both lenses as well as I think both are stellar at least reputation wise


Daniel
danielchtong is offline   Reply With Quote
Old May 25, 2008, 11:01 AM   #4
Senior Member
 
bigdawg's Avatar
 
Join Date: Feb 2005
Location: Thach Alabama
Posts: 14,981
Default

Use them in the real world!

Dawg

bigdawg is offline   Reply With Quote
Old May 25, 2008, 11:24 AM   #5
Senior Member
 
mtngal's Avatar
 
Join Date: Nov 2005
Location: Frazier Park, CA
Posts: 16,052
Default

The correct way is the way that Kjell said. Make sure you write down everything you can, otherwise you won't remember (I always do).

My problem is that I'll always have something changed or use some setting thatI didn't mean to, or else end up with a bunch of very boring pictures that don't show much difference. So I tend to just go walking around, taking pictures. Sometimes (since I have two cameras), I'll take some pictures with the lenses on one camera and then switch them - that doesn't give you a truly direct comparison, but I've found that I've managed to get a better selection of shooting conditions, and will be able to judge if I like the lens better on one camera or another (I sometimes do). By the time I do this once or twice, I get a good idea of which one I'd prefer, because sometimes the differences are small and not readily apparent with test shots of charts.
mtngal is offline   Reply With Quote
Old May 25, 2008, 2:18 PM   #6
Senior Member
 
Join Date: Jul 2006
Location: Tumbleweed, Arizona
Posts: 1,381
Default

Hi Rodney,

I am an engineer and we try to do this on computer systems, and there is always something that goes wrong, the first few runs. So long about the 5th try we get everything stable - maybe.

Take a look at Daniel's thread, because your going to have the same problem.

http://forums.steves-digicams.com/fo...mp;forum_id=94

He had 2 lenses with different speeds. Thus, trying to compare each of them at the same f stop will inadvertantly give an advantage to one and bias the other, throwing off the results.

Probably the best way is to take all the advice given here, select a well lit area, with a tripod, 2 sec delay, mirror up, etc , mount one lens, and take an image at each f stop setting for each lens, without changing anything else on the camera body. Also record the setup, however the meta data on the images should also record all of this. This still may not be perfect since the shutter speed may vary across the time that you take the images due to changes in the ambient light conditions. I would also use something like ISO 100 for the best image possible for comparision.

This way you have an entire series of images with hopefully a single variable. Then examine them at your leasure. You will probably then find the sweet spot for each lens' f stop. I.e., say - f8 on one and f6 on the other. I would then compare the images at these setting to make a determination of what if either one is the best.

I tried somewhat the same idea, but using several lens at 16, 17 and 18mm. Everything went fine untill I looked at them and then found that the sun had changed a bit and on one of the images the f stop (in automatic) was different, but the shutter speed was the same. So there is always something to go wrong.

The other thing, I too have a K100D and since it does not have all of the capability of a K10D, your at the mercy of some of the automation. Like forcing the f stop, and shutter speed, however there is a button on the back right hand side that should lock in these that is used for stitching ALE or something.

Well - the Inlaws are flying out on Tuesday and we are "blitizing" the house - so back to cleaning, as I hear my wife calling...

Just some ideas.....

interested_observer is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 7:01 AM.