DA* 250mm image smaller than DA* 200mm image

russvarley · 02-17-2022, 04:48 PM

Hello everyone

My two long lenses are causing me some head scratching.The picture taken with the lens set at 250mm (bottom image) appears further away than the picture taken with the 200mm prime lens (top image). Both pictures were taken at the same time, from the same place with my KP. Shouldn't the 250mm picture appear nearer/bigger than the 200mm or am I missing something? Any explanation appreciated even if it is "your lens is broken".

Many thanks

Russ

Attached Images

bertwert · 02-17-2022, 04:57 PM - **3 Likes**

This is focus breathing - the 60-250 is well known for it. The rated focal length is focused at infinity, and if you focus close the effect is more pronounced. Some lenses are much worse at this than others

vonBaloney · 02-17-2022, 04:59 PM - **2 Likes**

The 250 is from a zoom, right? Welcome to something called "focus-breathing" which occurs with primes as well, but generally much less so. (It occurs with internally focusing lenses.) What it means is you only get the stated max focal length when focused at infinity, and when you are closer (and especially if you are within only a few feet), the real focal length is much less. For instance my Pentax 18-250 tops out at about 180mm for close subjects.

**luftfluss** · 02-17-2022, 05:00 PM - **1 Like**

Originally posted by russvarley

Hello everyone

My two long lenses are causing me some head scratching.The picture taken with the lens set at 250mm (bottom image) appears further away than the picture taken with the 200mm prime lens (top image). Both pictures were taken at the same time, from the same place with my KP. Shouldn't the 250mm picture appear nearer/bigger than the 200mm or am I missing something? Any explanation appreciated even if it is "your lens is broken".

Many thanks

Russ

Welcome to the wonderful world of focus breathing.

The DA* 250/4 is noted to have a particularly extravagant case of it.

Paul the Sunman · 02-17-2022, 06:12 PM - **1 Like**

Yep, focus breathing. The DFA* 70-200 does it too at close focusing distances. It's a "feature" of certain zoom optical designs. I don't really consider it a bug or flaw. It is what it is, part of the character and nature of the lens. If you want big close focussing, get a macro.

**UncleVanya** · 02-17-2022, 06:50 PM - **1 Like**

The effect on that lens diminishes as you move farther away. At 10m the effect is much reduced and before 30m I think it is gone.

---------- Post added 02-17-22 at 08:52 PM ----------

Originally posted by Paul the Sunman

Yep, focus breathing. The DFA* 70-200 does it too at close focusing distances. It's a "feature" of certain zoom optical designs. I don't really consider it a bug or flaw. It is what it is, part of the character and nature of the lens. If you want big close focussing, get a macro.

It is a feature of internal focusing designs. The zoom design is likely important also but even primes can suffer from this.

normhead · 02-17-2022, 06:53 PM - **1 Like**

Originally posted by UncleVanya

The effect on that lens diminishes as you move farther away. At 10m the effect is much reduced and before 30m I think it is gone.

---------- Post added 02-17-22 at 08:52 PM ----------

It is a feature of internal focusing designs. The zoom design is likely important also but even primes can suffer from this.

I bought one for use on birds 7 feet away.... what a shock. It was like my M-135 2.8 (Vivitar)roughly.

Funny you mention the DA*200. For close objects I use it instead of the DA*60-250, just for the reason you mention.

**UncleVanya** · 02-17-2022, 06:55 PM - **1 Like**

Originally posted by normhead

I bought one for use on birds 7 feet away.... what a shock. It was like my M-135 2.8 (Vivitar)roughly.

Amen... I found it out trying to shoot birds on a feeder. The DA* 50-135 is nearly as effective at that distance... the 135 Tak Bayonet is "longer".

normhead · 02-17-2022, 07:31 PM - **1 Like**

Originally posted by UncleVanya

Amen... I found it out trying to shoot birds on a feeder. The DA* 50-135 is nearly as effective at that distance... the 135 Tak Bayonet is "longer".

At least when I got the HD DA 1.4 TC it brought it into the same ballpark as the DA*200. The good thing being, as you get further away, it holds it's own.

However, bottom line, just another reason to love the DA 55-300 PLM.

**Bob 256** · 02-17-2022, 08:23 PM - **1 Like**

Pop a closeup lens on the front (distance to subject = 1/diopter value in meters - e.g. 1 diopter at 1 meter) and you'll get the 250mm back. Such a closeup lens arrangement will force the 250mm focus at infinity and you'll get the rated FL. Unfortunately, you need a closeup lens for every near distance you choose to make this work.

You could also keep your lens focused at infinity and use the proper extension tube and the image size would increase but in this case you might even get more than 250mm worth of magnification since the actual focal length increases without limit (theoretically anyway) as you get closer to your subject.

russvarley · 02-18-2022, 01:17 AM

Thank you for your replies everyone, really helpful

02-17-2022, 04:48 PM	#1
russvarley New Member Join Date: Feb 2022 Posts: 2	*DA 250mm image smaller than DA* 200mm image** Hello everyone My two long lenses are causing me some head scratching.The picture taken with the lens set at 250mm (bottom image) appears further away than the picture taken with the 200mm prime lens (top image). Both pictures were taken at the same time, from the same place with my KP. Shouldn't the 250mm picture appear nearer/bigger than the 200mm or am I missing something? Any explanation appreciated even if it is "your lens is broken". Many thanks Russ Attached Images

02-17-2022, 04:59 PM - 2 Likes	#3
vonBaloney Pentaxian Join Date: Oct 2011 Location: Albuquerque, NM Posts: 6,029	The 250 is from a zoom, right? Welcome to something called "focus-breathing" which occurs with primes as well, but generally much less so. (It occurs with internally focusing lenses.) What it means is you only get the stated max focal length when focused at infinity, and when you are closer (and especially if you are within only a few feet), the real focal length is much less. For instance my Pentax 18-250 tops out at about 180mm for close subjects. Last edited by vonBaloney; 02-17-2022 at 06:59 PM.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Canon EOS Rebel SL3 - smaller than the K100D Super	UncleVanya	General Photography	28	05-28-2019 03:18 AM
AF Spot mode: hidden fact revealed - AF point is 30% smaller than in "select"	beholder3	Pentax DSLR Discussion	17	09-14-2018 12:15 AM
Can you shoot smaller than 40mp with the 645D?	Sperdynamite	Pentax Medium Format	14	11-02-2011 07:23 AM
Pentax EVIL NC-1 has smaller sensor than APS-C - your opinion?	ogl	Pentax News and Rumors	1096	08-02-2011 06:52 AM
Which Zoom Lens? "Tamron AF 18-250mm", "Pentax-DA 18-250mm" or "Sigma 18-250mm"	hoomanshb	Pentax SLR Lens Discussion	4	07-30-2010 09:50 AM

02-17-2022, 04:57 PM - 3 Likes	#2
bertwert Veteran Member Join Date: Jun 2015 Location: Golden, BC Posts: 15,173	This is focus breathing - the 60-250 is well known for it. The rated focal length is focused at infinity, and if you focus close the effect is more pronounced. Some lenses are much worse at this than others

02-17-2022, 05:00 PM - 1 Like	#4
luftfluss Site Supporter Join Date: Jun 2011 Location: NJ Photos: Gallery \| Albums Posts: 11,619	Originally posted by russvarley Hello everyone My two long lenses are causing me some head scratching.The picture taken with the lens set at 250mm (bottom image) appears further away than the picture taken with the 200mm prime lens (top image). Both pictures were taken at the same time, from the same place with my KP. Shouldn't the 250mm picture appear nearer/bigger than the 200mm or am I missing something? Any explanation appreciated even if it is "your lens is broken". Many thanks Russ Welcome to the wonderful world of focus breathing. The DA* 250/4 is noted to have a particularly extravagant case of it.

02-17-2022, 06:12 PM - 1 Like	#5
Paul the Sunman Pentaxian Join Date: Aug 2011 Location: Melbourne Photos: Gallery Posts: 4,843	Yep, focus breathing. The DFA* 70-200 does it too at close focusing distances. It's a "feature" of certain zoom optical designs. I don't really consider it a bug or flaw. It is what it is, part of the character and nature of the lens. If you want big close focussing, get a macro.

02-17-2022, 06:50 PM - 1 Like	#6
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,407	The effect on that lens diminishes as you move farther away. At 10m the effect is much reduced and before 30m I think it is gone. ---------- Post added 02-17-22 at 08:52 PM ---------- Originally posted by Paul the Sunman Yep, focus breathing. The DFA* 70-200 does it too at close focusing distances. It's a "feature" of certain zoom optical designs. I don't really consider it a bug or flaw. It is what it is, part of the character and nature of the lens. If you want big close focussing, get a macro. It is a feature of internal focusing designs. The zoom design is likely important also but even primes can suffer from this.

02-17-2022, 06:53 PM - 1 Like	#7
normhead Pentaxian Join Date: Jun 2007 Location: Near Algonquin Park Photos: Gallery \| Albums Posts: 40,451	Originally posted by UncleVanya The effect on that lens diminishes as you move farther away. At 10m the effect is much reduced and before 30m I think it is gone. ---------- Post added 02-17-22 at 08:52 PM ---------- It is a feature of internal focusing designs. The zoom design is likely important also but even primes can suffer from this. I bought one for use on birds 7 feet away.... what a shock. It was like my M-135 2.8 (Vivitar)roughly. Funny you mention the DA200. For close objects I use it instead of the DA60-250, just for the reason you mention.

02-17-2022, 06:55 PM - 1 Like	#8
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,407	Originally posted by normhead I bought one for use on birds 7 feet away.... what a shock. It was like my M-135 2.8 (Vivitar)roughly. Amen... I found it out trying to shoot birds on a feeder. The DA* 50-135 is nearly as effective at that distance... the 135 Tak Bayonet is "longer".

02-17-2022, 07:31 PM - 1 Like	#9
normhead Pentaxian Join Date: Jun 2007 Location: Near Algonquin Park Photos: Gallery \| Albums Posts: 40,451	Originally posted by UncleVanya Amen... I found it out trying to shoot birds on a feeder. The DA* 50-135 is nearly as effective at that distance... the 135 Tak Bayonet is "longer". At least when I got the HD DA 1.4 TC it brought it into the same ballpark as the DA*200. The good thing being, as you get further away, it holds it's own. However, bottom line, just another reason to love the DA 55-300 PLM.

02-17-2022, 08:23 PM - 1 Like	#10
Bob 256 Site Supporter Join Date: Jun 2008 Location: Idaho Photos: Gallery Posts: 2,375	Pop a closeup lens on the front (distance to subject = 1/diopter value in meters - e.g. 1 diopter at 1 meter) and you'll get the 250mm back. Such a closeup lens arrangement will force the 250mm focus at infinity and you'll get the rated FL. Unfortunately, you need a closeup lens for every near distance you choose to make this work. You could also keep your lens focused at infinity and use the proper extension tube and the image size would increase but in this case you might even get more than 250mm worth of magnification since the actual focal length increases without limit (theoretically anyway) as you get closer to your subject.

02-18-2022, 01:17 AM	#11
russvarley New Member Join Date: Feb 2022 Posts: 2 Original Poster	Thank you for your replies everyone, really helpful