Am I reading this riight ? The Pentax 18-135 WR is sharper than Tamron 17-50 F2.8 ?

photoleet · 04-22-2012, 11:09 PM

18-135 review - Pentax SMC-DA 18-135mm f/3.5-5.6 ED AL [IF] WR - Review / Lens Test - Analysis

17-50 review - Tamron AF 17-50mm f/2.8 SP XR Di II LD Aspherical [IF] (Canon) - Review / Test Report - Analysis

Or am I reading those MTF charts wrong ?

**luftfluss** · 04-22-2012, 11:18 PM

Originally posted by StDevious

18-135 review - Pentax SMC-DA 18-135mm f/3.5-5.6 ED AL [IF] WR - Review / Lens Test - Analysis

17-50 review - Tamron AF 17-50mm f/2.8 SP XR Di II LD Aspherical [IF] (Canon) - Review / Test Report - Analysis

Or am I reading those MTF charts wrong ?

Well, first of all, you're comparing a lens on an 8MP camera vs a lens on a 16MP camera, so the sensors are not comparable, and also:

"Please note that the tests results are not comparable across the different systems!" - that's highlighted in blue on the lens test index apges

adpo · 04-23-2012, 01:38 AM

pretty sure you're reading the data wrong, what i'm getting is that the tamron is quite a bit faster at equivalent apertures, especially in the corners

khenna · 03-07-2014, 04:59 AM

Originally posted by photoleet

18-135 review - Pentax SMC-DA 18-135mm f/3.5-5.6 ED AL [IF] WR - Review / Lens Test - Analysis

17-50 review - Tamron AF 17-50mm f/2.8 SP XR Di II LD Aspherical [IF] (Canon) - Review / Test Report - Analysis

Or am I reading those MTF charts wrong ?

Yes, you are reading the MTF charts wrong as PZ did Pentax SMC-DA 18-135mm f/3.5-5.6 ED AL [IF] WR - Review / Lens Test - Analysis REFOCUS THE BORDERS/CORNERS!

awaldram · 03-07-2014, 05:16 AM - **1 Like**

Originally posted by photoleet

18-135 review - Pentax SMC-DA 18-135mm f/3.5-5.6 ED AL [IF] WR - Review / Lens Test - Analysis

17-50 review - Tamron AF 17-50mm f/2.8 SP XR Di II LD Aspherical [IF] (Canon) - Review / Test Report - Analysis

Or am I reading those MTF charts wrong ?

Your reading them wrong

If your willing to ignore klauses warning on cross system comaparason then you need to normalise the graphes

to do this your divide the resoltuion with the max chart scale so for 24mm F4
Tamron = 2050/2150 = 95% of max system resoltuion
Pentax = 2598/2750 = 94% of max system resoltuion

so the Tamron os sharper @f4 24mm ......But that only works if your using the lens on 8Mp

the reason is the lens may well have a max resolution (itself) of 2200 lw/ph you will not see this on 8mp but switch to 16Mp (2750) and the lens suddenly cannot rise to the requirements of the sensor.

SO you might see figure like
Tamron 2170/2750 = 78% of max resoltuion

I'm not saying that is what would happen but that is why you cannot cross compare MTF figures.

You need to interprate them as a trend and be aware the lower the Mp tested the easier it is for a lens to shine.

In your two examples I woudl summerise as

The Tamron easily out performs the Pentax at the wide end where the Pentax edges are well beyond soft.
by 24mm the Pentax has caught up and portentially passed the Tamron give the Mp differences but still the Tamron has f2.8
once past 24mm the Tamron again shows it superioirty

But bear in mind this is a single lens and the images I've seen from the Pentax are not indicative of the results Klaus obtained being considerably better across the frame than those MTF figure would show.

normhead · 03-07-2014, 06:14 AM

Long answer

Owning both lenses and completely loving my 18-135, in it's range the Tamron is just better. At least for my lenses. Sharper, better micro-contrast, and without looking at the numbers I guess that means better controlled CA, because that usually increases the micro-contrast... I don't like the 17-50 as a walk around lens, you waste too much time in lens changes, but in a studio type setting, where I can have my lens bag on a chair beside me and in good relatively dust and wind free condition, I'll use the Tamron in it's focal length. And awaldram is completely correct on the perils of comparing lenses tested on different sensors. You can look at the graphs and do a rough comparison...but if two lenses are pretty close on different systems, you don't want to be making any decisions from the numbers alone. Because of sample variation, they may not be accurate at all. With the two lenses Klaus got, lens A may be slightly better than Lens B. But at your retailer the lens B he has is better than the lens A he has in stock. It could happen.

Short answer,
In the range from 17-50 the Tamron is better although at 24 mm the 18-135 is darn good.
At ƒ2.8 the Tamron is 100% better. (and in low light it will lock focus on a K-3 in practically pitch darkness.)
At 51mm to 135 mm the 18-135 is 100% better.

They are not the same type of lens.

**Rondec** · 03-07-2014, 07:37 AM

Echoing what others have said, you can't compare lenses across systems -- at least not with the absolute numbers. What you can say is that the Tamron has achieved maximal center sharpness by f4, borders are maximal at all focal lengths by f5.6. On the other hand, the 18-135 is all over the place through the focal range, but borders are pretty weak at 18mm and above 80mm, even stopped down. Distortion is obviously worse on the 18-135.

But honestly, you can't really compare an f2.8 zoom with a 3x zoom to a variable aperture 8x zoom. Every lens is a compromise and the wider the zoom range, the more the compromises with regard to distortion, sharpness, and vignetting.

khenna · 03-07-2014, 01:59 PM

Originally posted by awaldram

Your reading them wrong

If your willing to ignore klauses warning on cross system comaparason then you need to normalise the graphes

to do this your divide the resoltuion with the max chart scale so for 24mm F4
Tamron = 2050/2150 = 95% of max system resoltuion
Pentax = 2598/2750 = 94% of max system resoltuion

so the Tamron os sharper @f4 24mm ......But that only works if your using the lens on 8Mp

the reason is the lens may well have a max resolution (itself) of 2200 lw/ph you will not see this on 8mp but switch to 16Mp (2750) and the lens suddenly cannot rise to the requirements of the sensor.

SO you might see figure like
Tamron 2170/2750 = 78% of max resoltuion

I'm not saying that is what would happen but that is why you cannot cross compare MTF figures.

You need to interprate them as a trend and be aware the lower the Mp tested the easier it is for a lens to shine.

In your two examples I woudl summerise as

The Tamron easily out performs the Pentax at the wide end where the Pentax edges are well beyond soft.
by 24mm the Pentax has caught up and portentially passed the Tamron give the Mp differences but still the Tamron has f2.8
once past 24mm the Tamron again shows it superioirty

But bear in mind this is a single lens and the images I've seen from the Pentax are not indicative of the results Klaus obtained being considerably better across the frame than those MTF figure would show.

I meant that Photozone admittted that the MTF charts of the Pentax 18-135 are wrong as

Quote:

However, regarding the field curvature you should stop down to f/11 in order to make sure that the corners are at least somewhat in-focus. THIS DOES NOT SHOW UP IN THE CHART BECAUSE WE REFOCUS THE BORDERS/CORNERS!

So the MTF charts don't make much sense.

normhead · 03-07-2014, 02:40 PM

Originally posted by khenna

I meant that Photozone admittted that the MTF charts of the Pentax 18-135 are wrong as So the MTF charts don't make much sense.

I've noticed with that lens you can keep the subject in the centre in focus and have pretty good focus on the wall behind it. It could be that this different points in focus could work to your advantage in some circumstances. But I've never seen corners with my lens Klaus saw with his. Pentax should have exchanged his copy for a better one. Or maybe as lens rentals suggested, they only have the equipment to test for centre sharp. Maybe they certified it as within spec without even knowing what the edges were like.

ElJamoquio · 09-04-2014, 01:22 PM

Originally posted by khenna

I meant that Photozone admittted that the MTF charts of the Pentax 18-135 are wrong as So the MTF charts don't make much sense.

I have a pic of a landscape at infinity and 135mm. Accidentally took it 'wide open', but wide open on that lens is F/5.6 so it's not a ridiculous thing to do.

The corners are just bad, bad, bad, bad. Really bad. At infinity.

normhead · 09-04-2014, 01:39 PM

Originally posted by ElJamoquio

I have a pic of a landscape at infinity and 135mm. Accidentally took it 'wide open', but wide open on that lens is F/5.6 so it's not a ridiculous thing to do.

The corners are just bad, bad, bad, bad. Really bad. At infinity.

That's when you change to your 60-250 ElJay.. I use my 60-250 for landscape quite often.

audiobomber · 09-04-2014, 02:17 PM

Originally posted by ElJamoquio

I have a pic of a landscape at infinity and 135mm. Accidentally took it 'wide open', but wide open on that lens is F/5.6 so it's not a ridiculous thing to do.

The corners are just bad, bad, bad, bad. Really bad. At infinity.

Could we see the photo? I don't find the 18-135 as bad as all that. Maybe yours just sucks.

JinDesu · 09-04-2014, 02:33 PM

The 18-135 is surprisingly sharp in the center. Corners, not so much.

https://farm6.staticflickr.com/5574/15090000256_724feaaf02_o.jpg - 18mm F4 (almost wide open)
https://farm4.staticflickr.com/3876/14926312929_5bf0fffc06_o.jpg - 135mm F5.6 (closer focus)

I didn't think it was bad at 135mm F5.6 infinity focus, but I don't have the lens with me to test.

ElJamoquio · 09-04-2014, 03:30 PM

Originally posted by audiobomber

Could we see the photo? I don't find the 18-135 as bad as all that. Maybe yours just sucks.

Prepping for a trip right now. Might be able to post it tonight.

**skunktail** · 09-04-2014, 04:07 PM

Originally posted by normhead

Owning both lenses and completely loving my 18-135, in it's range the Tamron is just better. At least for my lenses.

Norm, You beat me to this comment.

Ignoring the test charts, I carry the 18-135 for weather resistance, the Tamron for image quality.
and ultimately, we don't buy lenses to shoot test-charts, we buy them to take photos.

04-22-2012, 11:09 PM	#1
photoleet Veteran Member Join Date: Jul 2011 Location: DMV Photos: Albums Posts: 431	Am I reading this riight ? The Pentax 18-135 WR is sharper than Tamron 17-50 F2.8 ? 18-135 review - Pentax SMC-DA 18-135mm f/3.5-5.6 ED AL [IF] WR - Review / Lens Test - Analysis 17-50 review - Tamron AF 17-50mm f/2.8 SP XR Di II LD Aspherical [IF] (Canon) - Review / Test Report - Analysis Or am I reading those MTF charts wrong ?

03-07-2014, 05:16 AM - 1 Like	#5
awaldram Veteran Member Join Date: May 2008 Location: Hampshire Photos: Gallery Posts: 732	Originally posted by photoleet 18-135 review - Pentax SMC-DA 18-135mm f/3.5-5.6 ED AL [IF] WR - Review / Lens Test - Analysis 17-50 review - Tamron AF 17-50mm f/2.8 SP XR Di II LD Aspherical [IF] (Canon) - Review / Test Report - Analysis Or am I reading those MTF charts wrong ? Your reading them wrong If your willing to ignore klauses warning on cross system comaparason then you need to normalise the graphes to do this your divide the resoltuion with the max chart scale so for 24mm F4 Tamron = 2050/2150 = 95% of max system resoltuion Pentax = 2598/2750 = 94% of max system resoltuion so the Tamron os sharper @f4 24mm ......But that only works if your using the lens on 8Mp the reason is the lens may well have a max resolution (itself) of 2200 lw/ph you will not see this on 8mp but switch to 16Mp (2750) and the lens suddenly cannot rise to the requirements of the sensor. SO you might see figure like Tamron 2170/2750 = 78% of max resoltuion I'm not saying that is what would happen but that is why you cannot cross compare MTF figures. You need to interprate them as a trend and be aware the lower the Mp tested the easier it is for a lens to shine. In your two examples I woudl summerise as The Tamron easily out performs the Pentax at the wide end where the Pentax edges are well beyond soft. by 24mm the Pentax has caught up and portentially passed the Tamron give the Mp differences but still the Tamron has f2.8 once past 24mm the Tamron again shows it superioirty But bear in mind this is a single lens and the images I've seen from the Pentax are not indicative of the results Klaus obtained being considerably better across the frame than those MTF figure would show. Last edited by awaldram; 03-07-2014 at 05:25 AM.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Pentax 50-135 vs Tamron 70-200 + 28-75	dr_romix	Pentax SLR Lens Discussion	43	07-28-2012 09:36 AM
Pentax M 100 2.8 vs f4: which is sharper?	whojammyflip	Pentax SLR Lens Discussion	16	04-06-2012 04:38 PM
For Sale - Sold: K7, 18-55 WR, Tamron SP 70-150/2.8 and Pentax Broken 50-135/2.8	lynch1234	Sold Items	12	06-13-2011 11:06 AM
Tamron AF 90mm f/2.8 Di SP A/M 1:1 Macro vs Pentax 50-135	KAR200D	Pentax SLR Lens Discussion	17	06-10-2011 09:50 AM
Tamron 17-50 or Pentax DA18-135?	yurko_yr	Pentax SLR Lens Discussion	29	03-27-2011 06:16 AM

04-22-2012, 11:18 PM	#2
luftfluss Site Supporter Join Date: Jun 2011 Location: NJ Photos: Gallery \| Albums Posts: 11,619	Originally posted by StDevious 18-135 review - Pentax SMC-DA 18-135mm f/3.5-5.6 ED AL [IF] WR - Review / Lens Test - Analysis 17-50 review - Tamron AF 17-50mm f/2.8 SP XR Di II LD Aspherical [IF] (Canon) - Review / Test Report - Analysis Or am I reading those MTF charts wrong ? Well, first of all, you're comparing a lens on an 8MP camera vs a lens on a 16MP camera, so the sensors are not comparable, and also: "Please note that the tests results are not comparable across the different systems!" - that's highlighted in blue on the lens test index apges

04-23-2012, 01:38 AM	#3
adpo Veteran Member Join Date: Apr 2011 Location: Arizona Photos: Gallery Posts: 888	pretty sure you're reading the data wrong, what i'm getting is that the tamron is quite a bit faster at equivalent apertures, especially in the corners

03-07-2014, 04:59 AM	#4
khenna New Member Join Date: Nov 2013 Posts: 12	Originally posted by photoleet 18-135 review - Pentax SMC-DA 18-135mm f/3.5-5.6 ED AL [IF] WR - Review / Lens Test - Analysis 17-50 review - Tamron AF 17-50mm f/2.8 SP XR Di II LD Aspherical [IF] (Canon) - Review / Test Report - Analysis Or am I reading those MTF charts wrong ? Yes, you are reading the MTF charts wrong as PZ did Pentax SMC-DA 18-135mm f/3.5-5.6 ED AL [IF] WR - Review / Lens Test - Analysis REFOCUS THE BORDERS/CORNERS!

03-07-2014, 06:14 AM	#6
normhead Pentaxian Join Date: Jun 2007 Location: Near Algonquin Park Photos: Gallery \| Albums Posts: 40,451	Long answer Owning both lenses and completely loving my 18-135, in it's range the Tamron is just better. At least for my lenses. Sharper, better micro-contrast, and without looking at the numbers I guess that means better controlled CA, because that usually increases the micro-contrast... I don't like the 17-50 as a walk around lens, you waste too much time in lens changes, but in a studio type setting, where I can have my lens bag on a chair beside me and in good relatively dust and wind free condition, I'll use the Tamron in it's focal length. And awaldram is completely correct on the perils of comparing lenses tested on different sensors. You can look at the graphs and do a rough comparison...but if two lenses are pretty close on different systems, you don't want to be making any decisions from the numbers alone. Because of sample variation, they may not be accurate at all. With the two lenses Klaus got, lens A may be slightly better than Lens B. But at your retailer the lens B he has is better than the lens A he has in stock. It could happen. Short answer, In the range from 17-50 the Tamron is better although at 24 mm the 18-135 is darn good. At ƒ2.8 the Tamron is 100% better. (and in low light it will lock focus on a K-3 in practically pitch darkness.) At 51mm to 135 mm the 18-135 is 100% better. They are not the same type of lens.

03-07-2014, 07:37 AM	#7
Rondec Loyal Site Supporter Join Date: Mar 2009 Location: Gladys, Virginia Photos: Gallery Posts: 27,653	Echoing what others have said, you can't compare lenses across systems -- at least not with the absolute numbers. What you can say is that the Tamron has achieved maximal center sharpness by f4, borders are maximal at all focal lengths by f5.6. On the other hand, the 18-135 is all over the place through the focal range, but borders are pretty weak at 18mm and above 80mm, even stopped down. Distortion is obviously worse on the 18-135. But honestly, you can't really compare an f2.8 zoom with a 3x zoom to a variable aperture 8x zoom. Every lens is a compromise and the wider the zoom range, the more the compromises with regard to distortion, sharpness, and vignetting.

03-07-2014, 01:59 PM	#8
khenna New Member Join Date: Nov 2013 Posts: 12	Originally posted by awaldram Your reading them wrong If your willing to ignore klauses warning on cross system comaparason then you need to normalise the graphes to do this your divide the resoltuion with the max chart scale so for 24mm F4 Tamron = 2050/2150 = 95% of max system resoltuion Pentax = 2598/2750 = 94% of max system resoltuion so the Tamron os sharper @f4 24mm ......But that only works if your using the lens on 8Mp the reason is the lens may well have a max resolution (itself) of 2200 lw/ph you will not see this on 8mp but switch to 16Mp (2750) and the lens suddenly cannot rise to the requirements of the sensor. SO you might see figure like Tamron 2170/2750 = 78% of max resoltuion I'm not saying that is what would happen but that is why you cannot cross compare MTF figures. You need to interprate them as a trend and be aware the lower the Mp tested the easier it is for a lens to shine. In your two examples I woudl summerise as The Tamron easily out performs the Pentax at the wide end where the Pentax edges are well beyond soft. by 24mm the Pentax has caught up and portentially passed the Tamron give the Mp differences but still the Tamron has f2.8 once past 24mm the Tamron again shows it superioirty But bear in mind this is a single lens and the images I've seen from the Pentax are not indicative of the results Klaus obtained being considerably better across the frame than those MTF figure would show. I meant that Photozone admittted that the MTF charts of the Pentax 18-135 are wrong as Quote: However, regarding the field curvature you should stop down to f/11 in order to make sure that the corners are at least somewhat in-focus. THIS DOES NOT SHOW UP IN THE CHART BECAUSE WE REFOCUS THE BORDERS/CORNERS! So the MTF charts don't make much sense.

03-07-2014, 02:40 PM	#9
normhead Pentaxian Join Date: Jun 2007 Location: Near Algonquin Park Photos: Gallery \| Albums Posts: 40,451	Originally posted by khenna I meant that Photozone admittted that the MTF charts of the Pentax 18-135 are wrong as So the MTF charts don't make much sense. I've noticed with that lens you can keep the subject in the centre in focus and have pretty good focus on the wall behind it. It could be that this different points in focus could work to your advantage in some circumstances. But I've never seen corners with my lens Klaus saw with his. Pentax should have exchanged his copy for a better one. Or maybe as lens rentals suggested, they only have the equipment to test for centre sharp. Maybe they certified it as within spec without even knowing what the edges were like.

09-04-2014, 01:22 PM	#10
ElJamoquio Veteran Member Join Date: Feb 2011 Posts: 4,873	Originally posted by khenna I meant that Photozone admittted that the MTF charts of the Pentax 18-135 are wrong as So the MTF charts don't make much sense. I have a pic of a landscape at infinity and 135mm. Accidentally took it 'wide open', but wide open on that lens is F/5.6 so it's not a ridiculous thing to do. The corners are just bad, bad, bad, bad. Really bad. At infinity.

09-04-2014, 01:39 PM	#11
normhead Pentaxian Join Date: Jun 2007 Location: Near Algonquin Park Photos: Gallery \| Albums Posts: 40,451	Originally posted by ElJamoquio I have a pic of a landscape at infinity and 135mm. Accidentally took it 'wide open', but wide open on that lens is F/5.6 so it's not a ridiculous thing to do. The corners are just bad, bad, bad, bad. Really bad. At infinity. That's when you change to your 60-250 ElJay.. I use my 60-250 for landscape quite often.

09-04-2014, 02:17 PM	#12
audiobomber Veteran Member Join Date: May 2008 Location: Sudbury, Ontario Photos: Albums Posts: 6,806	Originally posted by ElJamoquio I have a pic of a landscape at infinity and 135mm. Accidentally took it 'wide open', but wide open on that lens is F/5.6 so it's not a ridiculous thing to do. The corners are just bad, bad, bad, bad. Really bad. At infinity. Could we see the photo? I don't find the 18-135 as bad as all that. Maybe yours just sucks.

09-04-2014, 02:33 PM	#13
JinDesu Veteran Member Join Date: Jun 2011 Location: New York City Photos: Gallery Posts: 5,638	The 18-135 is surprisingly sharp in the center. Corners, not so much. https://farm6.staticflickr.com/5574/15090000256_724feaaf02_o.jpg - 18mm F4 (almost wide open) https://farm4.staticflickr.com/3876/14926312929_5bf0fffc06_o.jpg - 135mm F5.6 (closer focus) I didn't think it was bad at 135mm F5.6 infinity focus, but I don't have the lens with me to test.

09-04-2014, 03:30 PM	#14
ElJamoquio Veteran Member Join Date: Feb 2011 Posts: 4,873	Originally posted by audiobomber Could we see the photo? I don't find the 18-135 as bad as all that. Maybe yours just sucks. Prepping for a trip right now. Might be able to post it tonight.

09-04-2014, 04:07 PM	#15
skunktail Site Supporter Join Date: Jan 2013 Location: Sydney, NSW Photos: Gallery \| Albums Posts: 287	Originally posted by normhead Owning both lenses and completely loving my 18-135, in it's range the Tamron is just better. At least for my lenses. Norm, You beat me to this comment. Ignoring the test charts, I carry the 18-135 for weather resistance, the Tamron for image quality. and ultimately, we don't buy lenses to shoot test-charts, we buy them to take photos.