Depth of field and sharpness with manual lenses

rodrigogalvao · 01-30-2023, 06:38 PM

I basically use manual lenses on my cameras (a Pentax-A 28mm f2.8 and a Pentax-A 50mm f2 on a K5 or K30).

I wonder if anyone has ever compared the depth of field using the aperture ring on the lenses versus the digital aperture in camera - and if you noticed any difference in results, ever in depth of field or sharpness.

**Just1MoreDave** · 01-30-2023, 06:59 PM - **1 Like**

I have, a long time ago. I was curious because A lenses have two different mechanisms for setting the aperture, and I wanted to make sure they both agreed after reassembly. I saw no difference and there shouldn't be, unless a lens has problems. You may see metering differences because the camera can use matrix metering with the A position but switches to center weighted off the A position.

Fogel70 · 01-30-2023, 10:27 PM

If you use the aperture ring in other modes than M-mode the lens will only use wide open aperture. And you have to use stop down metering in M-mode which may not as reliable as using the normal wide open metering.

So any lens with A-position it is usually recmended to use them in A-position on digital bodies.

Also if using aperture ring the camera will not save the f-number used in exif data.

**GUB** · 01-31-2023, 12:09 AM

Originally posted by rodrigogalvao

I wonder if anyone has ever compared the depth of field using the aperture ring on the lenses versus the digital aperture in camera - and if you noticed any difference in results, ever in depth of field or sharpness.

The only way for them to vary in DOF or sharpness is if they stop down to different f stops. If so variations in exposure would be the giveaway. Easy to spot in manual mode and in auto modes you would have to take shutter speed into account. I use my A series mostly via the ring but very occasionally use the A mode - never seen any difference.

StiffLegged · 01-31-2023, 12:14 AM - **1 Like**

Originally posted by rodrigogalvao

I basically use manual lenses on my cameras (a Pentax-A 28mm f2.8 and a Pentax-A 50mm f2 on a K5 or K30).

I wonder if anyone has ever compared the depth of field using the aperture ring on the lenses versus the digital aperture in camera - and if you noticed any difference in results, ever in depth of field or sharpness.

I have three A series optics: a lens is a lens is a lens. Just be aware that those depth of field scales were made for film and you might be slightly disappointed when using a higher-resolution digital camera compared to a film body. Review your results before walking on to the next shot.

Fogel70 · 01-31-2023, 02:32 AM - **1 Like**

Originally posted by GUB

The only way for them to vary in DOF or sharpness is if they stop down to different f stops. If so variations in exposure would be the giveaway. Easy to spot in manual mode and in auto modes you would have to take shutter speed into account. I use my A series mostly via the ring but very occasionally use the A mode - never seen any difference.

It may not be so easy, as stop down metering may not give the same meter reading as wide open metering. At least not on a DSLR.
Because of the focus screen used with stop down metering on DSLR may not give the same linear response on metering as wide open metering.

pschlute · 01-31-2023, 02:36 AM

Originally posted by rodrigogalvao

I wonder if anyone has ever compared the depth of field using the aperture ring on the lenses versus the digital aperture in camera

As pointed out above, if you move the aperture ring off the "A" setting, you need to use Manual Exposure mode (or B or X-Sync) if you want the lens to stop down during capture. If you try and use any of the Auto modes like P or TAv the camera will default to Av mode but the lens will not stop down.

There should be no difference when using Manual exposure mode, in how the lens stops down to the selected aperture during capture, whether you have selected aperture via the ring or via the camera e-dial.

AfterPentax Mark II · 01-31-2023, 04:51 AM

Originally posted by pschlute

As pointed out above, if you move the aperture ring off the "A" setting, you need to use Manual Exposure mode (or B or X-Sync) if you want the lens to stop down during capture. If you try and use any of the Auto modes like P or TAv the camera will default to Av mode but the lens will not stop down.

There should be no difference when using Manual exposure mode, in how the lens stops down to the selected aperture during capture, whether you have selected aperture via the ring or via the camera e-dial.

On the Super A, however, one of the features was when in Tv mode with the aperture ring set to A, the camera would set the aperture to any value as it was able to use continuous steps. I do not know if the later film camera's and the modern digital camera's did/do the same. It was never stipulated with any of the digital camera's when using DA or DFA lenses that the body has that same feature. When the aperture ring was set to A in Av mode the Super A did also use continuous steps for the exposure time. In Auto mode it chose the best setting for the exposure using continuous steps. In M mode it takes the usual steps. This is one of the reasons that the Super A gave you those brilliant results as to colour and contrast. It was one of the reasons I traded in my ME Super for the Super A. As to your question: it seems hard to compare and get a trustworthy result as you do not know if the digital camera has the same feature as the camera for which these lenses were originally designed.

pschlute · 01-31-2023, 05:41 AM - **1 Like**

Originally posted by AfterPentax Mark II

On the Super A

Yes the Super-A/Program-A was very advanced for it's time.

I have no idea if that was carried on in later film models or indeed into digital.

mikesbike · 01-31-2023, 02:13 PM

Originally posted by rodrigogalvao

I basically use manual lenses on my cameras (a Pentax-A 28mm f2.8 and a Pentax-A 50mm f2 on a K5 or K30).

I wonder if anyone has ever compared the depth of field using the aperture ring on the lenses versus the digital aperture in camera - and if you noticed any difference in results, ever in depth of field or sharpness.

I'm not sure I am understanding the exact nature of your inquiry, but you do not have to engage the aperture ring to make use of the distance and DOF scale on the lens. After using these scales to determine the aperture best for the purpose, you simply set the aperture as indicated via the camera's aperture control. However, there is only so much room on a lens for a DOF scale, which of course then has to be more approximate than an outboard DOF scale can be.

I do not think your K-30 has one, but your K-5 has optical DOF viewing, which is using your own eyes to evaluate what is or is not sharp, as long as the lighting is adequate to do so. When using this device, the lens will stop down to your chosen aperture, which will make for darker viewing. This control is at the far travel of the On/Off lever around the shutter button. If practical, it would seem best to go ahead and use the DOF scale on the lens, such as it is, and shooting in Av or M mode, use the camera's control to set the aperture as indicated, then do a double check by using the K-5's optical viewing through the VF. Finally, take a test shot to see if it is satisfactory. Another important factor- those lenses and their DOF scale were designed for FF use, not APS-C. With APS-C there will be a bit more DOF than there would be using that lens on a 35mm film body or a FF DSLR.

rodrigogalvao · 01-31-2023, 05:17 PM

Thanks for all your answers! I´ll some tests and compare the results, including the use of hyperfocal distance with lens set to infinity vs focus peak. There are some images that i recently took during a trip to Bolivia that seems not so good.

**Lowell Goudge** · 01-31-2023, 08:11 PM

Just to add a little “quirk” into the discussion of manual vs automatic aperture many years ago I found that some lenses have different behaviour.

The tamron XR di 28-75/2.8 has ani error in the auto aperture mechanism, where at F2.8 it under exposes by 1/2-1 stop and the error is linear to an over exposure of 1/2 - 1 stop at F32. It drove me nuts for years.manually setting exposure it was fone

**GUB** · 01-31-2023, 08:16 PM

Originally posted by rodrigogalvao

Thanks for all your answers! I´ll some tests and compare the results

If you are going to the trouble of a test then make sure you do it in manual mode with the same shutter speed and iso. Then if there is any variation in f stop from using the aperture ring vs using the A setting it will be obvious in the exposure.

pschlute · 01-31-2023, 11:04 PM - **1 Like**

Originally posted by rodrigogalvao

Thanks for all your answers! I´ll some tests and compare the results

One other thing that may be worth mentioning. I have an extensive collection of old manual focus lenses (K,M,A), and a few of them won't quite focus to infinity. The lens indicates it is on infinity but examination of the photo reveals it didn't quite make it. You may want to check that out too.

**GUB** · 01-31-2023, 11:46 PM

Originally posted by pschlute

One other thing that may be worth mentioning. I have an extensive collection of old manual focus lenses (K,M,A), and a few of them won't quite focus to infinity. The lens indicates it is on infinity but examination of the photo reveals it didn't quite make it. You may want to check that out too.

really good point.
Focus on something the lens can definitely focus past and compare that sharpness to a subject in the distance.
This definitely is an issue with old lenses.
Another quite common possibility is it is focusing past infinity and you are hitting the stop on distant subjects presuming that the stop is at infinity.

01-30-2023, 06:38 PM	#1
rodrigogalvao New Member Join Date: Apr 2020 Posts: 11	Depth of field and sharpness with manual lenses I basically use manual lenses on my cameras (a Pentax-A 28mm f2.8 and a Pentax-A 50mm f2 on a K5 or K30). I wonder if anyone has ever compared the depth of field using the aperture ring on the lenses versus the digital aperture in camera - and if you noticed any difference in results, ever in depth of field or sharpness.

01-31-2023, 02:32 AM - 1 Like	#6
Fogel70 Pentaxian Join Date: Sep 2009 Location: Stockholm, Sweden Photos: Albums Posts: 2,887	Originally posted by GUB The only way for them to vary in DOF or sharpness is if they stop down to different f stops. If so variations in exposure would be the giveaway. Easy to spot in manual mode and in auto modes you would have to take shutter speed into account. I use my A series mostly via the ring but very occasionally use the A mode - never seen any difference. It may not be so easy, as stop down metering may not give the same meter reading as wide open metering. At least not on a DSLR. Because of the focus screen used with stop down metering on DSLR may not give the same linear response on metering as wide open metering. Last edited by Fogel70; 01-31-2023 at 02:40 AM.

01-31-2023, 02:13 PM	#10
mikesbike Pentaxian Join Date: Dec 2016 Location: Southeastern Michigan Posts: 4,321	Originally posted by rodrigogalvao I basically use manual lenses on my cameras (a Pentax-A 28mm f2.8 and a Pentax-A 50mm f2 on a K5 or K30). I wonder if anyone has ever compared the depth of field using the aperture ring on the lenses versus the digital aperture in camera - and if you noticed any difference in results, ever in depth of field or sharpness. I'm not sure I am understanding the exact nature of your inquiry, but you do not have to engage the aperture ring to make use of the distance and DOF scale on the lens. After using these scales to determine the aperture best for the purpose, you simply set the aperture as indicated via the camera's aperture control. However, there is only so much room on a lens for a DOF scale, which of course then has to be more approximate than an outboard DOF scale can be. I do not think your K-30 has one, but your K-5 has optical DOF viewing, which is using your own eyes to evaluate what is or is not sharp, as long as the lighting is adequate to do so. When using this device, the lens will stop down to your chosen aperture, which will make for darker viewing. This control is at the far travel of the On/Off lever around the shutter button. If practical, it would seem best to go ahead and use the DOF scale on the lens, such as it is, and shooting in Av or M mode, use the camera's control to set the aperture as indicated, then do a double check by using the K-5's optical viewing through the VF. Finally, take a test shot to see if it is satisfactory. Another important factor- those lenses and their DOF scale were designed for FF use, not APS-C. With APS-C there will be a bit more DOF than there would be using that lens on a 35mm film body or a FF DSLR. Last edited by mikesbike; 01-31-2023 at 02:21 PM.

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01-30-2023, 06:59 PM - 1 Like	#2
Just1MoreDave Site Supporter Join Date: Feb 2007 Location: Aurora, CO Photos: Gallery \| Albums Posts: 6,187	I have, a long time ago. I was curious because A lenses have two different mechanisms for setting the aperture, and I wanted to make sure they both agreed after reassembly. I saw no difference and there shouldn't be, unless a lens has problems. You may see metering differences because the camera can use matrix metering with the A position but switches to center weighted off the A position.

01-30-2023, 10:27 PM	#3
Fogel70 Pentaxian Join Date: Sep 2009 Location: Stockholm, Sweden Photos: Albums Posts: 2,887	If you use the aperture ring in other modes than M-mode the lens will only use wide open aperture. And you have to use stop down metering in M-mode which may not as reliable as using the normal wide open metering. So any lens with A-position it is usually recmended to use them in A-position on digital bodies. Also if using aperture ring the camera will not save the f-number used in exif data.

01-31-2023, 12:09 AM	#4
GUB Loyal Site Supporter Join Date: Aug 2012 Location: Wanganui Photos: Gallery \| Albums Posts: 5,346	Originally posted by rodrigogalvao I wonder if anyone has ever compared the depth of field using the aperture ring on the lenses versus the digital aperture in camera - and if you noticed any difference in results, ever in depth of field or sharpness. The only way for them to vary in DOF or sharpness is if they stop down to different f stops. If so variations in exposure would be the giveaway. Easy to spot in manual mode and in auto modes you would have to take shutter speed into account. I use my A series mostly via the ring but very occasionally use the A mode - never seen any difference.

01-31-2023, 12:14 AM - 1 Like	#5
StiffLegged Pentaxian Join Date: Jan 2018 Photos: Gallery Posts: 3,594	Originally posted by rodrigogalvao I basically use manual lenses on my cameras (a Pentax-A 28mm f2.8 and a Pentax-A 50mm f2 on a K5 or K30). I wonder if anyone has ever compared the depth of field using the aperture ring on the lenses versus the digital aperture in camera - and if you noticed any difference in results, ever in depth of field or sharpness. I have three A series optics: a lens is a lens is a lens. Just be aware that those depth of field scales were made for film and you might be slightly disappointed when using a higher-resolution digital camera compared to a film body. Review your results before walking on to the next shot.

01-31-2023, 02:36 AM	#7
pschlute Moderator Loyal Site Supporter Join Date: Mar 2007 Location: Surrey, UK Photos: Gallery Posts: 6,522	Originally posted by rodrigogalvao I wonder if anyone has ever compared the depth of field using the aperture ring on the lenses versus the digital aperture in camera As pointed out above, if you move the aperture ring off the "A" setting, you need to use Manual Exposure mode (or B or X-Sync) if you want the lens to stop down during capture. If you try and use any of the Auto modes like P or TAv the camera will default to Av mode but the lens will not stop down. There should be no difference when using Manual exposure mode, in how the lens stops down to the selected aperture during capture, whether you have selected aperture via the ring or via the camera e-dial.

01-31-2023, 04:51 AM	#8
AfterPentax Mark II Pentaxian Join Date: Mar 2021 Posts: 1,178	Originally posted by pschlute As pointed out above, if you move the aperture ring off the "A" setting, you need to use Manual Exposure mode (or B or X-Sync) if you want the lens to stop down during capture. If you try and use any of the Auto modes like P or TAv the camera will default to Av mode but the lens will not stop down. There should be no difference when using Manual exposure mode, in how the lens stops down to the selected aperture during capture, whether you have selected aperture via the ring or via the camera e-dial. On the Super A, however, one of the features was when in Tv mode with the aperture ring set to A, the camera would set the aperture to any value as it was able to use continuous steps. I do not know if the later film camera's and the modern digital camera's did/do the same. It was never stipulated with any of the digital camera's when using DA or DFA lenses that the body has that same feature. When the aperture ring was set to A in Av mode the Super A did also use continuous steps for the exposure time. In Auto mode it chose the best setting for the exposure using continuous steps. In M mode it takes the usual steps. This is one of the reasons that the Super A gave you those brilliant results as to colour and contrast. It was one of the reasons I traded in my ME Super for the Super A. As to your question: it seems hard to compare and get a trustworthy result as you do not know if the digital camera has the same feature as the camera for which these lenses were originally designed.

01-31-2023, 05:41 AM - 1 Like	#9
pschlute Moderator Loyal Site Supporter Join Date: Mar 2007 Location: Surrey, UK Photos: Gallery Posts: 6,522	Originally posted by AfterPentax Mark II On the Super A Yes the Super-A/Program-A was very advanced for it's time. I have no idea if that was carried on in later film models or indeed into digital.

01-31-2023, 05:17 PM	#11
rodrigogalvao New Member Join Date: Apr 2020 Posts: 11 Original Poster	Thanks for all your answers! I´ll some tests and compare the results, including the use of hyperfocal distance with lens set to infinity vs focus peak. There are some images that i recently took during a trip to Bolivia that seems not so good.

01-31-2023, 08:11 PM	#12
Lowell Goudge Site Supporter Join Date: Jan 2007 Location: Toronto Photos: Gallery \| Albums Posts: 17,371	Just to add a little “quirk” into the discussion of manual vs automatic aperture many years ago I found that some lenses have different behaviour. The tamron XR di 28-75/2.8 has ani error in the auto aperture mechanism, where at F2.8 it under exposes by 1/2-1 stop and the error is linear to an over exposure of 1/2 - 1 stop at F32. It drove me nuts for years.manually setting exposure it was fone

01-31-2023, 08:16 PM	#13
GUB Loyal Site Supporter Join Date: Aug 2012 Location: Wanganui Photos: Gallery \| Albums Posts: 5,346	Originally posted by rodrigogalvao Thanks for all your answers! I´ll some tests and compare the results If you are going to the trouble of a test then make sure you do it in manual mode with the same shutter speed and iso. Then if there is any variation in f stop from using the aperture ring vs using the A setting it will be obvious in the exposure.

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01-31-2023, 11:04 PM - 1 Like	#14
pschlute Moderator Loyal Site Supporter Join Date: Mar 2007 Location: Surrey, UK Photos: Gallery Posts: 6,522	Originally posted by rodrigogalvao Thanks for all your answers! I´ll some tests and compare the results One other thing that may be worth mentioning. I have an extensive collection of old manual focus lenses (K,M,A), and a few of them won't quite focus to infinity. The lens indicates it is on infinity but examination of the photo reveals it didn't quite make it. You may want to check that out too.

01-31-2023, 11:46 PM	#15
GUB Loyal Site Supporter Join Date: Aug 2012 Location: Wanganui Photos: Gallery \| Albums Posts: 5,346	Originally posted by pschlute One other thing that may be worth mentioning. I have an extensive collection of old manual focus lenses (K,M,A), and a few of them won't quite focus to infinity. The lens indicates it is on infinity but examination of the photo reveals it didn't quite make it. You may want to check that out too. really good point. Focus on something the lens can definitely focus past and compare that sharpness to a subject in the distance. This definitely is an issue with old lenses. Another quite common possibility is it is focusing past infinity and you are hitting the stop on distant subjects presuming that the stop is at infinity.