Using a full frame lens on a cropped sensor body

A Quick FAQ for one of the most sensitive and hottest topics in forums. It stirs controversy not only because people don't fully understand, it causes anguish because people end up supplying answers to different questions.

Q1. Do I dial in a different ISO/shutter speed / f/no with the same lens on bodies with different sized sensors?
Ans: No, You use the same parameters

Q2. Do I get a different image "quality" if I use the same lens on different sensors?
Ans:

• It varies depending on some factors but overall, yes, the final image when enlarged from the sensor size to the final size of screen or print will show that the full frame image with less image noise, all things being equal. 
• It may not be exactly proportional to the sensor size ratios because all things are not always equal. 
• The increase in noise is due to the fact that the smaller sensor only sees a small part of the full frame image and you have to magnify the image more to fit the final size screen or print. 
• Some people want to explain it a different way and say that the smaller sensor has "lost" light - in one way, it has, because the smaller sensor cannot see part of the image. In another way, it has not - whatever light that does fall onto the sensor, is the same brightness per area.
• Also an issue is that people often want X megapixels (let us say 20 Mp) whether they use a cropped sensor camera or a full frame camera. That means that cropped sensor makers have to fit a higher pixel density (more pixels per area) onto a smaller sensor. This makes the pixel smaller on a cropped sensor camera. These are all theoretical design issues. At the end of the day, people compare real, practical cameras with real sensors - due to different technological edge, the superiority may not be proportional as prescribed by theory.

Q3. Will the amount of blur background be different when you use the same lens on different sized sensors for the same subject size in the frame.
Ans.

• Yes, there will be different background blur, all things being equal. This is where the notorious phrase - "f/2 on a MFT sensor is equivalent to f/... on a full frame sensor"
• A simplified visual simulator that you can interact with on the web is here:
  https://dofsimulator.net/en/
• An Android App that allows you to understand subject dimensions in the parameters of depth of field is the DOF and Hyperfocal Calculator by Cunning Dog.

Q4: If you fit a 50mm full frame lens on a cropped sensor body, what happens to the f/no?

Ans:

• The f/no stays the same - it is a property of the lens, not the camera body.

Q5: Isn't background blur the same as depth of field?

Ans: No, they are not the same. 

• Depth of field depends on camera to subject distance
• Background blur depends on camera to background distance

Q6. Will the inherent creaminess of a bokeh ball in the centre of the frame be different between the two bodies?
Ans. Likely the bokeh ball will be the same character of wiryness, onion skin, or bokeh ball shape.

Q7: Isn't bokeh the same as background blur?
Ans: Not, they are not the same. The original definition for bokeh is about the creaminess of the blur for the same amount of blur, not how blurred the background is.

Q8. Will the whole frame blur and bokeh effect be different between the two bodies with different sensor size with the same lens?
Ans. Yes, the full frame style of picture will be different because the smaller sensor does not show you the blurry bits and vignetting of the lens that is around the edge of the frame

Q9: If you fit a 50mm full frame lens onto say an MFT sensor body, will it become 100mm?
Ans: No.

• 50mm focal length is a property of the lens. 
• When you fit this lens on a cropped sensor body (whether it be MFT or APS-C), part of the image will not be seen by the sensor because the sensor is smaller (hence the name Cropped) than the Circle of Coverage of the full frame lens. 
• To ensure that you see the full height of the subject using a cropped sensor body, you will have to walk backwards - i.e. increase your camera to subject distance.
• People will then say that if you stand at the same spot but do not move back, you are using the equivalent of a 100mm lens on a full frame body, when you use a 50mm lens on a MFT body.

Having said all the above, let's look at an entertaining and illustrative video that combines some of these points together and..... potentially (if you didn't read above) fills your head with conflicting information (unless you sit down and calmly deconstruct the impact James is saying point by point)

Oh, Ok, so it wasn't that quick. Did you learn something?

For ease of access, here is a DOF calculator by PhotoPills

The Misconception about SOOC Raw

Recently I saw a question posed about which camera (or camera brand) had the better colour. I explained that each camera will likely have a different colour profile and it should not be viewed as a technical superiority, the merit is most often subjective and affected by artistic interpretations. In short, it's a matter of taste.

There is also a misconception that if one takes a raw file from the camera and displays it the preferred editing program of choice, without touching any adjustment sliders, that it is SOOC (Straight Out Of Camera) raw. This is not correct. In order for the editing program to create a display on screen for you to asses, it has to demosaic, apply colour profiles, tonal curves, sharpening, noise reduction and even lens corrections. It's a bit like the old Australian ad phrase - "Clayton's - its the drink you have when you are not having a drink". Every editing program has to apply "factory defaults" as determined by the program maker (as opposed to the camera maker). In most programs, you can replace the factory default with your preferred "look", either on a one by one image, or in batch with a Develop Preset or save that "look" to the default.  In the last case, that means whenever you bring in a raw file, this camera calibration will be applied.

As Lightroom is one of the most popular raw editing programs, here are some screenshots of where you go to set up your personalised import defaults.

Edit > Preferences in Lightroom

Import Dialog in Lightroom showing Import Presets and Develop Settings

Preferences Dialog in Adobe Camera Raw

Develop Presets Panel in Adobe Camera Raw

Here's a video explaining this:

And here is a video by Mark Wallace about how to use the Xrite Color Checker Passport with Lightroom to set reference profiles and switch and also to offset the neutral colour to a wamer or cooler white balance:

Learnt something?

Keep it Simple: Fill in Flash in harsh daylight

It's not hard to reduce shadows in harsh daylight, for general circumstances. Here's how.

Equipment used:

• Olympus OM-D E-M1 Mark 1
• Nissin i40 (for MFT cameras, able to support TTL and HSS)

Many people who eschew using flash, are used to P A or S (Program vs Aperture Priority vs Shutter Speed priority) for ambient light shooting. P A or S can be so convenient, you feel like using it all the time. When you fit the flash on, you want the flash to somehow work in with the situation. It seems natural to think like that. 

P A or S were designed for when the camera just measures the light in the scene, computes what ISO / Aperture / Shutter Speed is right to use. When you introduce the factor of Flash, the camera now has a conundrum - the flash will only show its hand when it fires, not during liveview before you press the shutter release. So the liveview estimates for ISO / Aperture / Shutter Speed may or may not be able to be fulfilled when you click.  In this case, the camera makers so far, have made assumptions on how to make this mechanism work for P A S. These assumptions may set limits on what you want to do and you may spend more time fighting these assumptions than making forward progress.

Do the Gordian Knot thing - take a deep breath and leave P A S alone. For this situation, use Manual Exposure on the camera body and take control of your destiny.

1. Switch to Manual Exposure on the Camera
2. Ensure Liveview Boost (on Olympus cameras, the jargon is different for other mirrorless cameras) is set to OFF so that Liveview will emulate the exposure if using ambient light alone - this is typically OFF under normal use.
3. Ensure that you are not using Silent Shutter.
4. Set the ISO to fixed ISO 200
5. Set the shutter speed to 1/250th sec
6. Set the f/no to f/5.6
7. Have look at Liveview, take a shot. Make it look reasonable - darken / brighten by changing the f/no but keep the shutter speed at or below 1/250th sec.  This is what I got:

In this photo, without flash, I've adjusted the settings so that the brighter leaves are pleasant but the leaves in shadow are a little dark

8. Now fit the flash, switch it on, ensure the flash is set to TTL Auto (on the Nissin i40, there are two choices on the flash dial - "A" for standard TTL Auto and "TTL" if you want to use an enhanced mode and adjust flash brightness compensation using the dials on the Nissin i40 - choose A)
9.  and ensure that the camera has the flash icon in Super Control Panel enabled. Simply point the camera at anything (not your eyes) and click just to check that the flash will fire when you click.
10. Take a photo with the flash thus ready.

Photo with flash on TTL auto but otherwise same settings as the previous image above.

Notice in this photo, the shadows have been lightened considerably. You can now change the f/no by a little bit if you want to tweak to taste.

If the ambient light changes considerably, you might want to adjust the f/no again but I'm assuming you're using this technique because it is constantly bright and harsh and the lighting is not volatile.

If you are happy with this look, that's it, no need to read anymore. 

For those who are looking for more blur in the background and they have a lens that opens to f/2 (or brighter) which allows a shallower depth of field, this is what you do next.

11. Fit the brighter lens, take off the flash or disable the flash from triggering.
12. Ensure the lens is set to f/2 or the bright aperture that you so desire. Take a shot without the flash.  ISO 200, 1/250th sec, camera on Manual Exposure. This is what you get:

Over bright exposure, with a bright f/2 lens, same ambient lighting as the previous photos

So you see, by ambient light itself without flash, the exposure is too bright. Using Liveview, you will want to adjust the shutter speed so that the photo does not bleach out. This makes a high shutter speed necessary. 

13. Take another shot, adjust the shutter speed faster so that the photo without flash looks nice enough. Let us say, I got a photo that was nice at 1/800th sec.
14. Fit the flash, enable the flash in the camera. You will see the shutter speed drop to 1/250th and no amount of camera dial twirling will make it rise. This is the stage when you want to enable High Speed Sync (HSS).
15. On the Nissin i40 (see pdf manual), you enable HSS by pressing the lighted green button on the flash for a few seconds until a white LED blinks near the right-hand dial on the flash. Once you see that blink, you can use the camera dial to raise the camera's shutter speed past 1/250th sec. So raise the camera's shutter speed to the shutter speed that you arrived at in step 13.
16. Take the shot with the flash firing. You'll get this:

So, a similarly pleasant shot as the one you got at f/5.6 with flash. 

This new shot is similar in exposure brightness to the one you got at f/5.6 with flash. However, this is at f/2 or brighter and you now have a blurred background.

That's it. You've survived Manual Exposure on the camera body with TTL Auto and HSS on the flash and used a bright aperture like f/2 for shallow depth of field bokeliciousness.

Like what you read? Learnt something from it?

I have other flash notes too.
Jargon:

MFT	Micro Four Thirds mirrorless cameras. These cameras have LiveView so that you can see what image will look like in ambient light before you click
TTL Flash	Through The Lens metering so that the camera can measure the light that the flash produces when the flash triggers and regulate it to the image brightness you have nominated HSS
HSS	High Speed Sync - Focal Plane Shutters have a limited maximum speed when used with flash (flash sync speed), typically 1/250th sec and in bright sun outdoors, you need a higher speed than that. So HSS (also called FP mode) was invented to pulse the flash light many many times during the exposure so that the camera body allows you to use a higher shutter speed than the flash sync speed
Focal Plane Shutter	There are several types of shutter used in the variety of cameras. DSLRs and interchangeable lens mirrorless cameras tend to use a Focal Plane Shutter. A Focal Plane Shutter at a shutter speed higher than Flash Sync Speed, produces a travelling slit to expose the sensor that is less than the full area of the sensor.

Photographing the Super Blue Red Moon (Lunar Eclipse)

The Moon before the eclipse. Tokina 200mm f/3.5 film era lens on an Olympus E-M1 Mark 1 with film era Komura Telemore II 2x magnification teleconvertor.  ISO 200 1/250 (f/8 on the lens, I think)

We've had a fun time trying to shoot the moon.  Some people make the activity look unbelievably easy, others encounter all kinds of difficulties that puzzle them. Here's a retrospective on my technique.

1. Separate the process of aiming vs focussing vs exposure - I use a mirrorless Liveview camera and these modern cameras excel at general photography but shooting the moon is a non standard activity. If you don't separate these concepts in your mind, you end up with a blurry white disc in an expanse of black sky.
2. Put the camera on a tripod. You will be waiting for the moon and taking several shots. I was around for from 11 pm to nearly 2 am so that's a long time to spend holding a heavy long lens pointing up in the sky.  For some gear, turn off image stabilisation if you trust your tripod is very steady and your tripod head to camera mount is rock steady. Some cameras automatically understand they don't need image stabilisation.
3. Use Manual Focus and Manual Exposure and Fixed ISO. See point 1

Aiming

Liveview cameras are usually set to emulate the scene and the exposure - if the exposure is very bright, the liveview will be bright and vice versa if dark. This presents a problem with shooting only the moon (it's different if you want the moon as part of a nightscape). If the camera thinks there is a lot of dark (i.e. the black sky) it will brighten the liveview to the extent that the moon in liveview will be like a blurry, white washed out disc. You don't want that, you can't assess the clarity of focus or anything.

Tip: Set the exposure metering of the camera to spot area. Point the spot at a lit portion of the moon. The camera will attempt to make liveview display that area as 18% grey, suitable for eye judgement and assessment.

Focussing

Now that you can see the moon clearly (see Aiming, above), you can manually focus. If the moon is very small because you do not have a high power telephoto / zoom, you might need to magnify which Liveview cameras often easily do. Toggle Focus Peaking (I like red outlines) - you can outline the edges of the moon with focus peaking colour. Focus Peaking sometimes does not represent perfect focus in general use but the moon is a bright disc in the black sky, it works well.

The moon is not a racing car or a sports player. It does move but not at the speed of lightning. And its distance from you does not change - it traverses the night sky, it doesn't run away or toward you. Once you have achieved focus, except for gear accidents, touching the lens etc... you do not need to change focus. It's essentially at infinity.

Exposure

First to appreciate the significance, read through these B & H articles (highlighted by +Margaret Wong)

• https://www.bhphotovideo.com/explora/photography/tips-and-solutions/22-tips-for-photographing-a-lunar-eclipse
• https://www.bhphotovideo.com/explora/photography/tips-and-solutions/14-tips-shooting-moon

The moon will be bright before eclipse. Rule of thumb is the Looney 11. 

All you need is a ballpark figure to set the fixed ISO / shutter speed / aperture on your camera. Remember you are using a digital camera - you can shoot and review exposure almost immediately, then adjust the setting. Of course, you need to know which way on those scales is brighter or darker. But within a few seconds, you can home in on the relevant exposure.

When the moon enters eclipse, the brightness changes a lot because now, the light from the sun is being blocked by the earth. (It's the lunar eclipse, duh!).  In this case, it will be a lot dimmer. You might have to go to ISO 1600 as opposed to Looney 16 when you used ISO 200. You might be down to 1/2 sec exposure time as opposed to 1/200th sec exposure during Looney 16.

Tokina 200mm 1/25sec with stacked Komura TCON X2 and Vivitar TCON X2  ISO 200 (f/3.5 I think) on Olympus E-M1 Mark 1

Be awake to that. It takes like forever to eclipse, then it's suddenly dark and remains dark for 10 or more minutes. If you are not awake to that, you would have left your manual exposure setting on Looney 11.

Tokina 200mm 1/4sec with stacked Komura TCON X2 Vivitar TCON X2  ISO 3200 (f/3.5 I think) on Olympus E-M1 Mark 1

When you figure out that your settings for exposure need brightening, you have to reconcile whether you want to increase ISO (which implies more image noise) or lengthen shutter speed (which risks blur from camera/tripod/moon movement)

Tokina 200mm 1/2sec with stacked Komura TCON X2 Vivitar TCON X2  ISO 3200 (f/3.5 I think) on Olympus E-M1 Mark 1

Then, you wait around until the eclipse clears and it's back to Looney 11

Tokina 200mm 1/15 sec with stacked Komura TCON X2 Vivitar TCON X2  ISO 400 (f/8 I think) on Olympus E-M1 Mark 1

Triggering

Under Looney 11 conditions, you may not need much care in holding the camera steady or triggering. You could even hand hold the camera and lens if you could hold your aim steady enough at such a high magnification. However, when shutter speeds lengthen, you want camera motion to be the least of your worries. You could use a remote control mechanism (wired remote control or camera phone app or tether) or you could just use the 12 second timer built into most cameras. If you are worried about shutter shock or you want even more time for the camera and nervous tripod to reach static state, use the vibration reduction delay built into the camera.

Colour

If you are shooting raw, you can adjust colour easily during post processing. However, you have to remember the colour of the moon. Why not shoot JPEG + Raw so you can easily have a reference. And set the White Balance in the camera to Sunny. Not Auto White Balance which will fade the colours to pale (the camera does not know what colour the moon should be)

But my photo isn't as sharp as I expect - I'm not seeing enough detail

The tips above are to give you a head start, a ballpark result where the moon does not look like a blurred white disc in the sky. If your photo isn't as sharp or as detailed as you expect or some trolls egg you on about, consider:

• How was the atmospheric haze/cloud cover during your shot?
• Have you got the best quality lenses for this type of work - what is their usual sharpness resolving power and micro contrast. What's the next level up in performance and cost? Do you want to pay that for this pursuit? Or maybe you could rent?
• Have you got enough magnification? Speaking in terms of "full frame" sensor, 800mm equivalent focal length is nice to have.
• Have you got enough image light/brightness. An f/2.8 lens would be nice. It does not stay as f/2.8 brightness if you stack on one or two optical teleconverters
• Have you got a really steady tripod/camera/lens combination that does not wobble at the slightest breeze?
• Have you got a sensor that will have low enough noise at ISO 3200?
• If you are using specialised 2000mm mirror lenses which are high magnifying power and suffer from thermal expansion/contraction that affects the focus point, you should be checking your focus more frequently.

Like what you read? Learnt something from it?