Should I send this lens back for decentering?

Outis · 11-13-2015, 07:54 AM

I ordered a Rokinon 14mm f/2.8, and the first copy I got was obviously decentered-- one side of the image was was far fuzzier than the other, even on a normal laptop screen, without zooming in to 100%. So, I exchanged it for another copy. This one also shows some decentering, though it's only noticeable at 100%. Should I exchange it, too? I really don't know what level of decentering falls under normal tolerances.

**luftfluss** · 11-13-2015, 08:11 AM

Is the decentering only noticeable wide open? For my usage, if the decentering was evident at f/4 I would return it.

stillshot2 · 11-13-2015, 08:12 AM

It's really up to you if it's worth it or not. You could post a full resolution sample photo for us to analyze if you wanted.

normhead · 11-13-2015, 08:14 AM - **1 Like**

Send it back.... for the most part it can't be corrected. Very few facilities have the ability to fix this. Lens rentals uses trial and error with shims. It's not going to get any better, if you start with defective, and it gets worse how bad will it get? The only way these companies are going to clue in is if every decentered lens is returned. Right now, so few people look for it they just assume they can get away with it. I recently sent a Sigma lens in because it was decentered and they replaced a few parts, but did nothing for the decentered image. It is pretty much only functional at ƒ8 and beyond. You paid for ƒ2.8 in both size and cost, Having to stop the lens down to get decent images is un-acceptable.

Go in with your game face on, calmly explain the situation, ask for another lens.

osv · 11-13-2015, 08:36 AM

the korean lenses are all pretty much known for that.

it's not uncommon to see people go through several copies before giving up.

**luftfluss** · 11-13-2015, 08:48 AM

Originally posted by normhead

Send it back.... for the most part it can't be corrected. Very few facilities have the ability to fix this. Lens rentals uses trial and error with shims. It's not going to get any better, if you start with defective, and it gets worse how bad will it get? The only way these companies are going to clue in is if every decentered lens is returned. Right now, so few people look for it they just assume they can get away with it. I recently sent a Sigma lens in because it was decentered and they replaced a few parts, but did nothing for the decentered image. It is pretty much only functional at ƒ8 and beyond. You paid for ƒ2.8 in both size and cost, Having to stop the lens down to get decent images is un-acceptable.

You are also paying for poor QC when you buy Samyang/Rokinon/etc. That's why each individual has to decide on what he/she can live with, and the trade-off between searching for the "perfect" copy - which could take months and multiple exchanges - and one that is sufficient for the need.

Quote:

Go in with your game face on, calmly explain the situation, ask for another lens.

The OP indicated he ordered the lens.

Na Horuk · 11-13-2015, 09:12 AM

Originally posted by Outis

So, I exchanged it for another copy. This one also shows some decentering, though it's only noticeable at 100%

Welcome to the club. Many of us sent back our first copy. Some even sent back the second.
I personally returned the first and got another, which is better, but not perfect. Its not a big problem, though. I mostly use the lens at f8, where DoF covers most of the decentering. For wide open photos, its not a problem, because I only shoot wide open for close up subjects, where DoF does not need to be perfectly centered. One problem is that I cannot use CA correction, since CA is different on different sides of the frame. The biggest problem is astrophotography! If you want to take star photos, where stars across the sky are sharp, then decentering can be a problem.
So decide what your priorities are.

Originally posted by Outis

I really don't know what level of decentering falls under normal tolerances.

The problem is that many UWA lenses have some degree of decentering. The decentering can be very slight and it already shows up at UWA focal lengths. Some UWA lenses have problems only at certain focus (like the Pentax 16-45mm, where the extended barrel at 16mm can bend a little, which is enough to be optically noticeable).

I know, its a hassle. Decentering and uncalibrated focus ring are the main problems with UWA Samyang lenses. Other than that, they are amazing. My 14mm is very sharp, despite its slightly diagonal DoF. Try to test the lens in the way you will be using it, and decide if it delivers what you need it to.
One other thing to keep in mind is that if you will buy a camera with a bigger sensor (film, FF), then this decentering can become even more noticeable in the edges.

---------- Post added 13th Nov 2015 at 17:20 ----------

If you want us to judge for you, take a photo at f2.8 near the minimum focus distance, of something like a coin on a newspaper. Use a tripod and 2 sec timer and lowest ISO. Feel free to use live view with focus peaking and digital zoom to achieve best focus. De-focus and re-focus to take another photo. Upload the one where you got the best focus. Put it on a website like Flickr where we can see the full size photo, as uploading it to this forum will cause automatic resizing, which will affect the image quality and make it harder to judge.

Outis · 11-13-2015, 09:20 AM

Yeah, the only thing I'm going to use this lens for is astrophotography, where the decentering wide open would be a problem. So, I think I'll exchange it for another copy.

Na Horuk · 11-13-2015, 10:40 AM

Still, do a test run first. Hope you have clear skies tonight

Suggest you find out where infinity focus lies on the focus ring before going out, though.

Outis · 11-13-2015, 02:51 PM

I mean, I live in urban Boston and don't have a car, so that's not really possible for me. I think I'll just try for another one.

goldenarrow · 11-14-2015, 10:52 PM - **1 Like**

Originally posted by normhead

Send it back.... for the most part it can't be corrected. Very few facilities have the ability to fix this. Lens rentals uses trial and error with shims. It's not going to get any better, if you start with defective, and it gets worse how bad will it get? The only way these companies are going to clue in is if every decentered lens is returned. Right now, so few people look for it they just assume they can get away with it. I recently sent a Sigma lens in because it was decentered and they replaced a few parts, but did nothing for the decentered image. It is pretty much only functional at ƒ8 and beyond. You paid for ƒ2.8 in both size and cost, Having to stop the lens down to get decent images is un-acceptable.

Go in with your game face on, calmly explain the situation, ask for another lens.

YES, SEND IT BACK!!!

Outis · 11-15-2015, 09:23 AM

YES, SIR!

normhead · 11-15-2015, 09:30 AM - **1 Like**

That's the spirit.

stevebrot · 11-15-2015, 03:11 PM

Send it back. Continuous quality improvement process relies on input from each point in the product manufacture, distribution, sale, and use flow. By refusing to accept readily detectable issues, one improves the product and the buyer experience for many others down at a later time.

Steve

goldenarrow · 11-15-2015, 03:19 PM

Originally posted by Outis

YES, SIR!

It is an interesting problem. You may get one back (third lens) that is fine, but maybe not. They will probably sell this as new since it is only slightly decentered. It is one big carp shoot nowadays......

11-13-2015, 07:54 AM	#1
Outis Veteran Member Join Date: Apr 2014 Location: Cambridge, MA Posts: 935	Should I send this lens back for decentering? I ordered a Rokinon 14mm f/2.8, and the first copy I got was obviously decentered-- one side of the image was was far fuzzier than the other, even on a normal laptop screen, without zooming in to 100%. So, I exchanged it for another copy. This one also shows some decentering, though it's only noticeable at 100%. Should I exchange it, too? I really don't know what level of decentering falls under normal tolerances.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
What should I do with this lens?	vagabond79	General Photography	25	02-18-2015 09:08 PM
Where can I send lens and camera for repair?	Bumblebee71	Troubleshooting and Beginner Help	2	04-08-2014 11:41 PM
Should I send my 50-135 for repair?	sebberry	Troubleshooting and Beginner Help	6	08-23-2013 12:40 AM
No Dealer -- How To Send Lens Back For Exchange	rparmar	Pentax SLR Lens Discussion	2	08-25-2008 01:31 PM
how much should i offer for this lens?	Tyler	Pentax SLR Lens Discussion	4	06-17-2007 06:43 AM

11-13-2015, 08:11 AM	#2
luftfluss Site Supporter Join Date: Jun 2011 Location: NJ Photos: Gallery \| Albums Posts: 11,627	Is the decentering only noticeable wide open? For my usage, if the decentering was evident at f/4 I would return it.

11-13-2015, 08:12 AM	#3
stillshot2 Pentaxian Join Date: Sep 2013 Location: Phoenix, AZ Photos: Albums Posts: 1,070	It's really up to you if it's worth it or not. You could post a full resolution sample photo for us to analyze if you wanted.

11-13-2015, 08:14 AM - 1 Like	#4
normhead Pentaxian Join Date: Jun 2007 Location: Near Algonquin Park Photos: Gallery \| Albums Posts: 40,451	Send it back.... for the most part it can't be corrected. Very few facilities have the ability to fix this. Lens rentals uses trial and error with shims. It's not going to get any better, if you start with defective, and it gets worse how bad will it get? The only way these companies are going to clue in is if every decentered lens is returned. Right now, so few people look for it they just assume they can get away with it. I recently sent a Sigma lens in because it was decentered and they replaced a few parts, but did nothing for the decentered image. It is pretty much only functional at ƒ8 and beyond. You paid for ƒ2.8 in both size and cost, Having to stop the lens down to get decent images is un-acceptable. Go in with your game face on, calmly explain the situation, ask for another lens.

11-13-2015, 08:36 AM	#5
osv Veteran Member Join Date: Mar 2007 Location: So Cal Photos: Gallery Posts: 2,080	the korean lenses are all pretty much known for that. it's not uncommon to see people go through several copies before giving up.

11-13-2015, 08:48 AM	#6
luftfluss Site Supporter Join Date: Jun 2011 Location: NJ Photos: Gallery \| Albums Posts: 11,627	Originally posted by normhead Send it back.... for the most part it can't be corrected. Very few facilities have the ability to fix this. Lens rentals uses trial and error with shims. It's not going to get any better, if you start with defective, and it gets worse how bad will it get? The only way these companies are going to clue in is if every decentered lens is returned. Right now, so few people look for it they just assume they can get away with it. I recently sent a Sigma lens in because it was decentered and they replaced a few parts, but did nothing for the decentered image. It is pretty much only functional at ƒ8 and beyond. You paid for ƒ2.8 in both size and cost, Having to stop the lens down to get decent images is un-acceptable. You are also paying for poor QC when you buy Samyang/Rokinon/etc. That's why each individual has to decide on what he/she can live with, and the trade-off between searching for the "perfect" copy - which could take months and multiple exchanges - and one that is sufficient for the need. Quote: Go in with your game face on, calmly explain the situation, ask for another lens. The OP indicated he ordered the lens.

11-13-2015, 09:12 AM	#7
Na Horuk Veteran Member Join Date: Feb 2012 Location: Slovenia, probably Photos: Gallery \| Albums Posts: 11,186	Originally posted by Outis So, I exchanged it for another copy. This one also shows some decentering, though it's only noticeable at 100% Welcome to the club. Many of us sent back our first copy. Some even sent back the second. I personally returned the first and got another, which is better, but not perfect. Its not a big problem, though. I mostly use the lens at f8, where DoF covers most of the decentering. For wide open photos, its not a problem, because I only shoot wide open for close up subjects, where DoF does not need to be perfectly centered. One problem is that I cannot use CA correction, since CA is different on different sides of the frame. The biggest problem is astrophotography! If you want to take star photos, where stars across the sky are sharp, then decentering can be a problem. So decide what your priorities are. Originally posted by Outis I really don't know what level of decentering falls under normal tolerances. The problem is that many UWA lenses have some degree of decentering. The decentering can be very slight and it already shows up at UWA focal lengths. Some UWA lenses have problems only at certain focus (like the Pentax 16-45mm, where the extended barrel at 16mm can bend a little, which is enough to be optically noticeable). I know, its a hassle. Decentering and uncalibrated focus ring are the main problems with UWA Samyang lenses. Other than that, they are amazing. My 14mm is very sharp, despite its slightly diagonal DoF. Try to test the lens in the way you will be using it, and decide if it delivers what you need it to. One other thing to keep in mind is that if you will buy a camera with a bigger sensor (film, FF), then this decentering can become even more noticeable in the edges. ---------- Post added 13th Nov 2015 at 17:20 ---------- If you want us to judge for you, take a photo at f2.8 near the minimum focus distance, of something like a coin on a newspaper. Use a tripod and 2 sec timer and lowest ISO. Feel free to use live view with focus peaking and digital zoom to achieve best focus. De-focus and re-focus to take another photo. Upload the one where you got the best focus. Put it on a website like Flickr where we can see the full size photo, as uploading it to this forum will cause automatic resizing, which will affect the image quality and make it harder to judge.

11-13-2015, 09:20 AM	#8
Outis Veteran Member Join Date: Apr 2014 Location: Cambridge, MA Posts: 935 Original Poster	Yeah, the only thing I'm going to use this lens for is astrophotography, where the decentering wide open would be a problem. So, I think I'll exchange it for another copy.

11-13-2015, 10:40 AM	#9
Na Horuk Veteran Member Join Date: Feb 2012 Location: Slovenia, probably Photos: Gallery \| Albums Posts: 11,186	Still, do a test run first. Hope you have clear skies tonight Suggest you find out where infinity focus lies on the focus ring before going out, though.

11-13-2015, 02:51 PM	#10
Outis Veteran Member Join Date: Apr 2014 Location: Cambridge, MA Posts: 935 Original Poster	I mean, I live in urban Boston and don't have a car, so that's not really possible for me. I think I'll just try for another one.

11-14-2015, 10:52 PM - 1 Like	#11
goldenarrow Veteran Member Join Date: Jun 2009 Location: Chicago Suburbs. Photos: Gallery Posts: 501	Originally posted by normhead Send it back.... for the most part it can't be corrected. Very few facilities have the ability to fix this. Lens rentals uses trial and error with shims. It's not going to get any better, if you start with defective, and it gets worse how bad will it get? The only way these companies are going to clue in is if every decentered lens is returned. Right now, so few people look for it they just assume they can get away with it. I recently sent a Sigma lens in because it was decentered and they replaced a few parts, but did nothing for the decentered image. It is pretty much only functional at ƒ8 and beyond. You paid for ƒ2.8 in both size and cost, Having to stop the lens down to get decent images is un-acceptable. Go in with your game face on, calmly explain the situation, ask for another lens. YES, SEND IT BACK!!!

11-15-2015, 09:23 AM	#12
Outis Veteran Member Join Date: Apr 2014 Location: Cambridge, MA Posts: 935 Original Poster	YES, SIR!

11-15-2015, 09:30 AM - 1 Like	#13
normhead Pentaxian Join Date: Jun 2007 Location: Near Algonquin Park Photos: Gallery \| Albums Posts: 40,451	That's the spirit.

11-15-2015, 03:11 PM	#14
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Send it back. Continuous quality improvement process relies on input from each point in the product manufacture, distribution, sale, and use flow. By refusing to accept readily detectable issues, one improves the product and the buyer experience for many others down at a later time. Steve

11-15-2015, 03:19 PM	#15
goldenarrow Veteran Member Join Date: Jun 2009 Location: Chicago Suburbs. Photos: Gallery Posts: 501	Originally posted by Outis YES, SIR! It is an interesting problem. You may get one back (third lens) that is fine, but maybe not. They will probably sell this as new since it is only slightly decentered. It is one big carp shoot nowadays......